diff --git a/examples/rbtree_bench.js b/benchmarks/rbtree_bench.js
similarity index 100%
rename from examples/rbtree_bench.js
rename to benchmarks/rbtree_bench.js
diff --git a/compare/registry.js b/compare/registry.js
deleted file mode 100644
index dc2342e..0000000
--- a/compare/registry.js
+++ /dev/null
@@ -1,32 +0,0 @@
-import { getInst, getType } from "../primitives/dynamic.js";
-import { SymbolBool, SymbolChar, SymbolDouble, SymbolInt, SymbolType, SymbolUnit } from "../primitives/types.js";
-import { symbolList, symbolProduct, symbolSet, symbolSum } from "../structures/types.js";
-import { compareBools, compareNumbers, compareStrings, compareUnits } from "./primitives.js";
-import { compareLists, compareProducts, compareSets, compareSums } from "./structures.js";
-import { compareTypes } from "./type.js";
-
-const typeSymbolToCmp = new Map([
-  [SymbolInt   , compareNumbers],
-  [SymbolChar  , compareStrings],
-  [SymbolDouble, compareNumbers],
-  [SymbolBool  , compareBools],
-  [SymbolUnit  , compareUnits],
-  [SymbolType  , compareTypes],
-
-  // these functions take extra comparison callbacks:
-  [symbolList   , compareLists],
-  [symbolProduct, compareProducts],
-  [symbolSum    , compareSums],
-  [symbolSet    , compareSets],
-]);
-
-export const makeCompareFn = type => {
-  return type.params.reduce(
-    (acc, cur) => acc(makeCompareFn(cur)),
-    typeSymbolToCmp.get(type.symbol)
-  );
-};
-
-export const compareDynamic = x => y =>
-  compareTypes(getType(x))(getType(y))
-    || makeCompareFn(getType(x))(getInst(x))(getInst(y));
diff --git a/examples/enum.js b/examples/enum.js
index 43223f4..8ca9301 100644
--- a/examples/enum.js
+++ b/examples/enum.js
@@ -1,13 +1,15 @@
-import { makeCompareFn } from "../compare/registry.js";
-import { Int, Unit } from "../primitives/types.js";
-import { unit } from "../primitives/unit.js";
-import { enumType, makeConstructors, makeMatchFn } from "../structures/enum.js";
-import { newProduct } from "../structures/product.js";
-import { lsType, prettyT } from "../structures/types.js";
+import { makeCompareFn } from "../lib/compare/registry.js";
+import { Int, Unit } from "../lib/primitives/primitive_types.js";
+import { unit } from "../lib/primitives/unit.js";
+import { makeConstructors, makeMatchFn } from "../lib/structures/enum.js";
+import { enumType } from "../lib/structures/enum.types.js";
+import { newProduct } from "../lib/structures/product.js";
+import { lsType } from "../lib/structures/type_constructors.js";
+import { prettyT } from "../lib/util/pretty.js";
 
 const variants = [
   newProduct("price")(Int),
-  newProduct("prices")(lsType(() =>Int)),
+  newProduct("prices")(lsType(_ => Int)),
   newProduct("not_found")(Unit),
 ];
 
@@ -19,7 +21,7 @@ console.log(" ", prettyT(myEnumType));
 const [newPrice, newPrices, newNotFound] = makeConstructors(variants);
 
 const price = newPrice(10);
-const prices = newPrices({ l: [20, 30] });
+const prices = newPrices([20, 30]);
 const notFound = newNotFound(unit);
 
 console.log("observe the encoding of different variant instances:");
@@ -29,7 +31,7 @@ console.log(" ", notFound);
 
 const myEnumToString = x => makeMatchFn(variants)(x)
   (price => `Price: ${price}`)
-  (prices => `Prices: ${prices.l}`)
+  (prices => `Prices: ${prices}`)
   (() => "Not found!");
 
 console.log("observe the generated match function in action:");
@@ -40,9 +42,9 @@ console.log(" ", myEnumToString(notFound));
 const compareMyEnum = makeCompareFn(myEnumType);
 
 console.log("observe the generated compare function in action:");
-console.log("  smaller ->", compareMyEnum(price)(prices));
-console.log("  bigger  ->", compareMyEnum(prices)(price));
-console.log("  bigger  ->", compareMyEnum(notFound)(price));
-console.log("  equal   ->", compareMyEnum(prices)(prices));
-console.log("  smaller ->", compareMyEnum(newPrice(5))(newPrice(6)));
-console.log("  bigger  ->", compareMyEnum(newPrices({ l: [5, 6] }))(newPrices({ l: [5, 5] })));
+console.log("  should be smaller ->", compareMyEnum(price)(prices));
+console.log("  should be bigger  ->", compareMyEnum(prices)(price));
+console.log("  should be bigger  ->", compareMyEnum(notFound)(price));
+console.log("  should be equal   ->", compareMyEnum(prices)(prices));
+console.log("  should be smaller ->", compareMyEnum(newPrice(5))(newPrice(6)));
+console.log("  should be bigger  ->", compareMyEnum(newPrices([5, 6]))(newPrices([5, 5])));
diff --git a/examples/generics.js b/examples/generics.js
index e307537..c60ba62 100644
--- a/examples/generics.js
+++ b/examples/generics.js
@@ -1,45 +1,37 @@
-import { Bool, Int } from "../primitives/types.js";
-import { fnType, lsType } from "../structures/types.js";
-import { assign, makeGeneric, unify } from "../generics/generics.js";
-import { prettyGenT, prettyT } from "../util/pretty.js";
+import { assign, makeGeneric, unify } from "../lib/generics/generics.js";
+import { prettyGenT } from "../lib/util/pretty.js";
+import { getDefaultTypeParser } from "../lib/parser/type_parser.js";
+
+const mkType = getDefaultTypeParser();
 
-// a -> Int
-const a_to_Int = makeGeneric(a => fnType(() => a)(() => Int));
-console.log((prettyGenT(a_to_Int))); // ∀a: (a -> Int)
-// Bool -> Int
-const Bool_to_Int = makeGeneric(() => fnType(() => lsType(() =>Bool))(() => Int));
-console.log((prettyGenT(Bool_to_Int))); // ∀: ([Bool] -> Int)
 console.log("should be: [Bool] -> Int")
-console.log(prettyGenT(unify(a_to_Int, Bool_to_Int)));
+console.log(prettyGenT(
+  unify(
+    mkType("∀a: (a -> Int)"),
+    makeGeneric(() => mkType("[Bool] -> Int")),
+  )
+));
 
-// (a -> a) -> b
-const fnType2 = makeGeneric((a,b) => fnType(() => fnType(a)(a))(() => b));
-// (Bool -> Bool) -> a
-const fnType3 = makeGeneric(a => fnType(() => fnType(Bool)(Bool))(() => a));
 console.log("should be: (Bool -> Bool) -> a");
-console.log(prettyT(unify(fnType2, fnType3)));
+console.log(prettyGenT(
+  unify(
+    mkType("∀a,b: (a -> a) -> b"),
+    mkType("∀a: (Bool -> Bool) -> a"),
+  )
+));
 
-// (a -> b) -> [a] -> [b]
-const mapFnType = makeGeneric((a,b) =>
-  fnType
-    (fnType(() => a)(() => b))
-    (fnType(() => lsType(() =>a))(() => lsType(() =>b))))
-// a -> a
-const idFnType = makeGeneric((_,__,c) =>
-  fnType(() => c)(() => c));
-console.log("should be: [c] -> [c]");
-console.log(prettyT(assign(mapFnType, idFnType)));
+console.log("should be: [a] -> [a]");
+console.log(prettyGenT(
+  assign(
+    mkType("∀a,b: (a -> b) -> [a] -> [b]"),
+    mkType("∀a: a -> a")
+  )
+));
 
-// (a -> Int) -> [a] -> a
-const weirdFnType = makeGeneric(a =>
-  fnType
-    (fnType(() => a)(() => Int))
-    (fnType
-      (lsType(() =>a))
-      (a)))
-// we call this function with parameter of type (b -> b) ...
-// giving these substitutions:
-//    a := b
-//    b := Int
 console.log("should be: [Int] -> Int");
-console.log(prettyT(assign(weirdFnType, idFnType)));
+console.log(prettyGenT(
+  assign(
+    mkType("∀a: (a -> Int) -> [a] -> a"),
+    mkType("∀a: a -> a")
+  )
+));
diff --git a/examples/int_or_bool.js b/examples/int_or_bool.js
deleted file mode 100644
index 4f773f9..0000000
--- a/examples/int_or_bool.js
+++ /dev/null
@@ -1,60 +0,0 @@
-import { assign, makeGeneric, unify } from "../generics/generics.js";
-import { Bool, Int } from "../primitives/types.js";
-import { newLeft, newRight, match } from "../structures/sum.js";
-import { fnType, sumType } from "../structures/types.js";
-import { pretty } from '../util/pretty.js';
-
-const IntOrBool = sumType(() => Int)(() => Bool);
-
-
-// console.log(int5);
-
-console.log(pretty(unify(
-  makeGeneric(() => IntOrBool),
-  makeGeneric(a => sumType(() => Int)(() => a)),
-)));
-
-const cipFunction = (x) => {
-  return match(x)({
-    left: x_as_int => (x_as_int === 5),
-    right: x_as_bool => false,
-  });
-}
-
-const cipFunctionType = fnType
-  (IntOrBool) // in
-  (Bool);
-
-// console.log(cipFunctionType);
-// console.log(IntOrBool);
-
-console.log(assign(
-  makeGeneric(() => cipFunctionType),
-  makeGeneric(() => IntOrBool),
-));
-
-console.log("calling newLeft with Int:");
-const typeAtCallSite = assign(
-  makeGeneric((a, b) =>
-    fnType
-      (a)
-      (sumType(() => a)(() => b))
-  ),
-  makeGeneric(() => Int));
-console.log(pretty(typeAtCallSite));
-
-
-console.log("calling cipFunction:");
-console.log(pretty(assign(
-  makeGeneric(() => cipFunctionType),
-  typeAtCallSite,
-)));
-
-console.log("valid function calls:");
-console.log(cipFunction(newLeft(5)));
-console.log(cipFunction(newLeft(7)));
-console.log(cipFunction(newRight(true)));
-
-console.log("invalid function calls:");
-console.log(cipFunction(5));
-console.log(cipFunction(newLeft("abc")));
diff --git a/examples/num.js b/examples/num.js
deleted file mode 100644
index 0fe79f4..0000000
--- a/examples/num.js
+++ /dev/null
@@ -1,28 +0,0 @@
-import { assign } from "../generics/generics.js";
-import { makeGeneric } from "../generics/generics.js";
-import { Double, Int } from "../primitives/types.js";
-import { fnType } from "../structures/types.js";
-import { pretty } from '../util/pretty.js';
-import { getMul, NumInstances } from "../typeclasses/num.js";
-import { numDictType } from "./num_type.js";
-
-const square = numDict => x => getMul(numDict)(x)(x);
-
-// NumDict a -> a -> a
-const squareFnType = makeGeneric(a => 
-  fnType
-    (numDictType(a))
-    (fnType(() => a)(() => a))
-  );
-
-console.log("should be: Int -> Int");
-console.log(pretty(assign(squareFnType, makeGeneric(() => numDictType(Int)))));
-
-console.log("should be: Double -> Double");
-console.log(pretty(assign(squareFnType, makeGeneric(() => numDictType(Double)))));
-
-// to call 'square' we need:
-//   - the type of our argument (=Int)
-//   - access to a mapping from types to their typeclass instantiation
-console.log("");
-console.log(square(NumInstances.get(Int))(42n)); // 1764n
diff --git a/examples/parser.js b/examples/parser.js
index e3d5701..0c5ce7c 100644
--- a/examples/parser.js
+++ b/examples/parser.js
@@ -1,5 +1,7 @@
-import { parse } from "../parser/parser.js";
-import { prettyGenT, prettyT } from "../util/pretty.js";
+import { getDefaultTypeParser }from "../lib/parser/type_parser.js";
+import { prettyGenT, prettyT } from "../lib/util/pretty.js";
+
+const parse = getDefaultTypeParser();
 
 console.log(prettyT(parse("Int"))); // Int
 
@@ -12,4 +14,3 @@ console.log(prettyT(parse("#0((Int * #0) + Unit)"))) // #0((Int ⨯ #0) + Unit)
 console.log(prettyGenT(parse("∀a: #0((a * #0) + Unit"))); // ∀a: #0((a ⨯ #0) + Unit)
 
 console.log(prettyGenT(parse("∀a,b,c,d: (a*b) + (c*d)"))); // ∀a,b,c,d: ((a ⨯ b) + (c ⨯ d))
-
diff --git a/examples/prompt.js b/examples/prompt.js
index f2cea2b..7372296 100644
--- a/examples/prompt.js
+++ b/examples/prompt.js
@@ -1,14 +1,15 @@
 import { select, number, input } from '@inquirer/prompts';
 import { ModulePoint } from "../lib/point.js";
-import { DefaultMap } from "../util/defaultmap.js";
-import { pretty } from '../util/pretty.js';
+import { DefaultMap } from "../lib/util/defaultmap.js";
+import { pretty } from '../lib/util/pretty.js';
 import { isFunction } from '../structures/types.js';
-import { ModuleStd } from '../stdlib.js';
+import { ModuleStd } from '../lib/stdlib.js';
 import { Double, GenericType, Int, SymbolT, Type } from "../primitives/types.js";
 import { eqType } from '../primitives/type.js';
 import { Top } from "../primitives/types.js";
-import { assignFn, makeGeneric, onlyOccurring } from '../generics/generics.js';
-import { prettyT } from '../util/pretty.js';
+import { assignFn, makeGeneric, onlyOccurring } from '../lib/generics/generics.js';
+import { prettyT } from '../lib/util/pretty.js';
+import { genUUID } from '../lib/util/random.js';
 
 
 // import {emitKeypressEvents} from 'node:readline';
@@ -289,7 +290,7 @@ async function createInstance(t) {
   else if (eqType(t)(SymbolT)) {
     console.log("Note: you are creating a new Symbol. Even if the description matches that of another symbol (e.g., \"Int\"), a new Symbol will be created that is unique and only equal to itself.");
     const symbolDescr = await input({message: "enter symbol description:"});
-    return Symbol(symbolDescr);
+    return symbolDescr + '__' + genUUID(16);
   }
   else {
     console.log("no prompt handler for creating new", prettyT(t));
diff --git a/examples/rbtree.js b/examples/rbtree.js
new file mode 100644
index 0000000..1ad2369
--- /dev/null
+++ b/examples/rbtree.js
@@ -0,0 +1,13 @@
+import createRBTree from "functional-red-black-tree";
+
+console.log("#############");
+console.log("## RB Tree ##");
+console.log("#############");
+
+// just a small experiment
+console.log(
+  createRBTree()
+    .insert(1)
+    .insert(1)
+    .insert(2)
+);
diff --git a/examples/recursive_types.js b/examples/recursive_types.js
index 5431b8d..fae27f8 100644
--- a/examples/recursive_types.js
+++ b/examples/recursive_types.js
@@ -1,8 +1,10 @@
-import { compareTypes } from "../compare/type.js";
-import { makeGeneric, substitute, unify } from "../generics/generics.js";
-import { Double, Int, Unit } from "../primitives/types.js";
-import { fnType, lsType, prodType, setType, sumType } from "../structures/types.js";
-import { prettyGenT, prettyT } from "../util/pretty.js";
+import { compareTypes } from "../lib/compare/type.js";
+import { makeGeneric, substitute, unify } from "../lib/generics/generics.js";
+import { Double, Int, Unit } from "../lib/primitives/primitive_types.js";
+import { fnType, lsType, prodType, sumType, setType } from "../lib/structures/type_constructors.js";
+import { prettyGenT, prettyT } from "../lib/util/pretty.js";
+
+Error.stackTraceLimit = Infinity;
 
 // some recursive types:
 
diff --git a/examples/versioning.js b/examples/versioning.js
index 70e63b8..f4688c0 100644
--- a/examples/versioning.js
+++ b/examples/versioning.js
@@ -1,7 +1,6 @@
 import { pretty } from "../util/pretty.js";
 import { newLiteral, transform, read, getReadDependencies, verifyValue } from "../versioning/value.js";
 import { merge, merge2, newSlot, overwrite } from "../versioning/slot.js";
-import createRBTree from "functional-red-black-tree";
 import { add, emptySet, RBTreeWrapper } from "../structures/set.js";
 import { compareNumbers } from "../compare/primitives.js";
 
@@ -77,39 +76,20 @@ console.log(pretty({sixSevenEightSlot}));
 // console.log("########################");
 // console.log("## Heterogeneous data ##");
 // console.log("########################");
-
 // // Slot<Int>
 // const numberOfSheepSlot  = newSlot(Symbol('numberOfSheep'))(newLiteral(5));
 // const alternativeNumberOfSheepSlot = newSlot(Symbol('alternativeNumberOfSheep'))(newLiteral(6));
 // // Slot<String>
 // const labelSlot  = newSlot(Symbol('label'))(newLiteral("number of sheep"));
-
 // const combineFn = newLiteral(label => numberOfSheep => `${label}: ${numberOfSheep}`)
-
 // // Slot<String>
 // const labelAndValueSlotA = overwrite(labelSlot)(
 //   transform(read(numberOfSheepSlot))(
 //     transform(read(labelSlot))(combineFn)));
-
 // const labelAndValueSlotB = overwrite(labelSlot)(
 //   transform(read(alternativeNumberOfSheepSlot))(
 //     transform(read(labelSlot))(combineFn)));
-      
 // console.log(
 //   add(add(emptySet(compareSlots(compareStrings)))(labelAndValueSlotA))(labelAndValueSlotB)
 // );
-
 // merge()(labelSlot)(labelAndValueSlot)
-
-
-console.log("#############")
-console.log("## RB Tree ##")
-console.log("#############")
-
-// just a small experiment
-console.log(
-  createRBTree()
-  .insert(1)
-  .insert(1)
-  .insert(2)
-);
diff --git a/extra/point/nominal.js b/extra/point/nominal.js
new file mode 100644
index 0000000..a888488
--- /dev/null
+++ b/extra/point/nominal.js
@@ -0,0 +1,23 @@
+export const cart2polar = ({x, y}) => {
+  const r = Math.sqrt(x*x + y*y);
+  const θ = Math.atan(y/x);
+  return {r, θ};
+};
+
+export const polar2cart = ({r, θ}) => {
+  const x = r * Math.cos(θ);
+  const y = r * Math.sin(θ);
+  return {x, y};
+}
+
+export const translate = dx => dy => ({x, y}) => {
+  return {left: x+dx, right: y+dy};
+}
+
+export const rotate = dθ => ({r, θ}) => {
+  return {r, θ: θ+dθ};
+}
+
+export const scale = dr => ({r, θ}) => {
+  return {r: r+dr, θ};
+}
diff --git a/extra/point/nominal.types.js b/extra/point/nominal.types.js
new file mode 100644
index 0000000..06ff6dc
--- /dev/null
+++ b/extra/point/nominal.types.js
@@ -0,0 +1,30 @@
+import { makeTypeParser } from "../../lib/parser/type_parser.js";
+import { Type } from "../../lib/primitives/primitive_types.js";
+import { makeTypeConstructor } from "../../lib/meta/type_constructor.js";
+import { cart2polar, polar2cart, rotate, scale, translate } from "./nominal.js";
+
+const PointCartesian2D = makeTypeConstructor('PCartesian2D__20bb64ce2cd52cfc6702f7d5d9bd1e60')(0);
+const PointPolar2D = makeTypeConstructor('PPolar2D__dd566869d57d440e0bc299c53cac3846')(0);
+
+const examplePoint = {x: 1, y: 2};
+
+const mkType = makeTypeParser({
+  extraPrimitives: [
+    ["PointCartesian2D", PointCartesian2D],
+    ["PointPolar2D", PointPolar2D],
+  ]
+});
+
+export const ModulePointNominal = [
+  {i: PointCartesian2D   , t: Type},
+  {i: PointPolar2D       , t: Type},
+
+  {i: examplePoint       , t: PointCartesian2D},
+
+  {i: cart2polar, t: mkType("PointCartesian2D -> PointPolar2D")},
+  {i: polar2cart, t: mkType("PointPolar2D -> PointCartesian2D")},
+
+  {i: translate, t: mkType("Double -> Double -> PointCartesian2D")},
+  {i: rotate   , t: mkType("Double -> PointPolar2D -> PointPolar2D")},
+  {i: scale    , t: mkType("Double -> PointPolar2D -> PointPolar2D")},
+];
diff --git a/extra/point/structural.types.js b/extra/point/structural.types.js
new file mode 100644
index 0000000..2904966
--- /dev/null
+++ b/extra/point/structural.types.js
@@ -0,0 +1,81 @@
+import { makeTypeParser } from "../../lib/parser/type_parser.js";
+import { makeModuleStruct } from "../../lib/structures/struct.types.js";
+import { makeTypeConstructor } from "../../lib/meta/type_constructor.js";
+import { newProduct } from "../../lib/structures/product.js";
+import { Double } from "../../lib/primitives/primitive_types.js";
+
+// Nominal types:
+const NPoint2DCartesian = makeTypeConstructor('PCartesian2D__7efe2dd14d9b036e2e83d6e4771c88ac')(0);
+const NPoint2DPolar = makeTypeConstructor('PPolar2D__9297b15478804ee209a91f1af943b67a')(0);
+
+// Structural types:
+
+const ModuleCartesian = makeModuleStruct([
+  newProduct("x")(Double),
+  newProduct("y")(Double),
+]);
+const ModulePolar = makeModuleStruct([
+  newProduct("r")(Double),
+  newProduct("θ")(Double),
+]);
+
+const [
+  {i: SPoint2DCartesian},
+  {i: newCartesian},
+  {i: getX},
+  {i: getY},
+] = ModuleCartesian;
+
+const [
+  {i: SPoint2DPolar},
+  {i: newPolar},
+  {i: getR},
+  {i: getΘ},
+] = ModulePolar;
+
+const cart2polar = cart => {
+  const x = getX(cart);
+  const y = getY(cart);
+  const r = Math.sqrt(x*x + y*y);
+  const θ = Math.atan(y/x);
+  return newPolar(r)(θ);
+};
+
+const polar2cart = polar => {
+  const r = getR(polar);
+  const θ = getΘ(polar);
+  const x = r * Math.cos(θ);
+  const y = r * Math.sin(θ);
+  return newCartesian(x)(y);
+};
+
+const mkType = makeTypeParser({
+  extraPrimitives: [
+    ["NPoint2DCartesian", NPoint2DCartesian],
+    ["NPoint2DPolar"    , NPoint2DPolar    ],
+  ],
+});
+
+const ModuleConversions = [
+  { i: NPoint2DCartesian , t: mkType("NPoint2DCartesian") },
+  { i: NPoint2DPolar     , t: mkType("NPoint2DPolar") },
+  { i: cart2polar        , t: mkType("NPoint2DCartesian -> NPoint2DPolar") },
+  { i: polar2cart        , t: mkType("NPoint2DPolar -> NPoint2DCartesian") },
+];
+
+const examplePointCart = newCartesian(1)(2);
+const examplePointPolar = newPolar(0)(5);
+
+const ModuleExamples = [
+  { i: examplePointCart  , t: SPoint2DCartesian },
+  { i: examplePointCart  , t: NPoint2DCartesian },
+  { i: examplePointPolar , t: SPoint2DPolar },
+  { i: examplePointPolar , t: NPoint2DPolar },
+];
+
+export const ModuleAll = [
+  ...ModuleCartesian,
+  ...ModulePolar,
+  ...ModuleConversions,
+  ...ModuleExamples,
+];
diff --git a/compare/primitives.js b/lib/compare/primitives.js
similarity index 73%
rename from compare/primitives.js
rename to lib/compare/primitives.js
index 5e15119..f043a1c 100644
--- a/compare/primitives.js
+++ b/lib/compare/primitives.js
@@ -22,8 +22,7 @@ export const compareBools = x => y => {
 };
 
 // The Unit-type has only one instance, which is equal to itself:
-export const compareUnits = x => y => 0;
+export const compareUnits = _ => _ => 0;
 
-// Note: dirty assumption that every symbol has unique description.
-// This will be fixed once we move from symbols to real UUIDs.
-export const compareSymbols = a => b => Number(a !== b) && compareStrings(a.description)(b.description);
+// Symbols are encoded as strings
+export const compareSymbols = a => b => compareStrings(a)(b);
diff --git a/lib/compare/primitives.types.js b/lib/compare/primitives.types.js
new file mode 100644
index 0000000..c7a17fc
--- /dev/null
+++ b/lib/compare/primitives.types.js
@@ -0,0 +1,11 @@
+import { getDefaultTypeParser } from "../parser/type_parser.js";
+import { compareBools, compareNumbers, compareSymbols, compareUnits } from "./primitives.js";
+
+const mkType = getDefaultTypeParser();
+
+export const ModuleComparePrimitives = [
+  {i: compareNumbers, t: mkType("Double -> Double -> Int")},
+  {i: compareBools  , t: mkType("Bool -> Bool -> Int")},
+  {i: compareUnits  , t: mkType("Unit -> Unit -> Int")},
+  {i: compareSymbols, t: mkType("SymbolT -> SymbolT -> Int")},
+];
diff --git a/lib/compare/registry.js b/lib/compare/registry.js
new file mode 100644
index 0000000..bfda00f
--- /dev/null
+++ b/lib/compare/registry.js
@@ -0,0 +1,35 @@
+import { getInst, getType } from "../primitives/dynamic.js";
+import { SymbolBool, SymbolChar, SymbolDouble, SymbolInt, SymbolType, SymbolUnit } from "../primitives/primitive_types.js";
+import { getHumanReadableName } from "../primitives/symbol.js";
+import { symbolDict, symbolList, symbolProduct, symbolSet, symbolSum } from "../structures/type_constructors.js";
+import { capitalizeFirstLetter } from "../util/util.js";
+import { compareBools, compareNumbers, compareStrings, compareUnits } from "./primitives.js";
+import { compareLists, compareProducts, compareSets, compareSums } from "./structures.js";
+import { compareTypes } from "./type.js";
+
+const typeSymbolToCmp = new Map([
+  [SymbolInt    , compareNumbers],
+  [SymbolChar   , compareStrings],
+  [SymbolDouble , compareNumbers],
+  [SymbolBool   , compareBools],
+  [SymbolUnit   , compareUnits],
+  [SymbolType   , compareTypes],
+
+  // these functions take extra comparison callbacks:
+  [symbolList    , compareLists],
+  [symbolProduct , compareProducts],
+  [symbolSum     , compareSums],
+  [symbolSet     , compareSets],
+  // [symbolDict    , compareDicts], TODO
+]);
+
+export const makeCompareFn = type => {
+  return type.params.reduce(
+    (acc, cur) => acc(makeCompareFn(cur(type))),
+    typeSymbolToCmp.get(type.symbol)
+  );
+};
+
+export const compareDynamic = x => y =>
+  compareTypes(getType(x))(getType(y))
+    || makeCompareFn(getType(x))(getInst(x))(getInst(y));
diff --git a/compare/structures.js b/lib/compare/structures.js
similarity index 76%
rename from compare/structures.js
rename to lib/compare/structures.js
index dbb9a9f..bde873a 100644
--- a/compare/structures.js
+++ b/lib/compare/structures.js
@@ -28,16 +28,22 @@ export const compareProducts = compareLeft => compareRight => x => y => {
 
 // (a -> a -> Int) -> (b -> b -> Int) -> (a | b) -> (a | b) -> Int
 export const compareSums = compareLeft => compareRight => x => y => {
-  return match(x)(newProduct
-    (leftValueX => match(y)(newProduct
-      (leftValueY => compareLeft(leftValueX)(leftValueY))
-      ((rightValueY) => -1) // x is 'left' and y is 'right' => x < y
-    ))
-    (rightValueX => match(y)(newProduct
-      (leftValueY => 1) // x is 'right' and y is 'left' => x > y
-      (rightValueY => compareRight(rightValueX)(rightValueY))
-    ))
-  );
+  // console.log("compareSums...", x, y)
+  return match(x)
+    (leftValueX => match(y)
+      (leftValueY => compareLeft(leftValueX)(leftValueY)) // both are left
+      ((_rightValueY) => {
+        // console.log("x is 'left' and y is 'right' => x < y")
+        return -1;
+      }) // x is 'left' and y is 'right' => x < y
+    )
+    (rightValueX => match(y)
+      (_leftValueY => {
+        // console.log("x is 'right' and y is 'left' => x > y");
+        return 1;
+      }) // x is 'right' and y is 'left' => x > y
+      (rightValueY => compareRight(rightValueX)(rightValueY)) // both are right
+    );
 };
 
 // (a -> a -> Int) -> {a} -> {a} -> Int
diff --git a/lib/compare/structures.types.js b/lib/compare/structures.types.js
new file mode 100644
index 0000000..16c8fce
--- /dev/null
+++ b/lib/compare/structures.types.js
@@ -0,0 +1,14 @@
+import { getDefaultTypeParser } from "../parser/type_parser.js";
+import { compareLists, compareProducts, compareSets, compareSums } from "./structures.js";
+
+const mkType = getDefaultTypeParser();
+
+export const ModuleCompareStructures = [
+  {i: compareLists, t: mkType("∀a: (a -> a -> Int) -> [a] -> [a] -> Int")},
+
+  {i: compareProducts, t: mkType("∀a,b: (a -> a -> Int) -> (b -> b -> Int) -> (a*b) -> (a*b) -> Int")},
+
+  {i: compareSums, t: mkType("∀a,b: (a -> a -> Int) -> (b -> b -> Int) -> (a+b) -> (a+b) -> Int")},
+
+  {i: compareSets, t: mkType("∀a: (a -> a -> Int) -> {a} -> {a} -> Int")},
+];
\ No newline at end of file
diff --git a/compare/type.js b/lib/compare/type.js
similarity index 86%
rename from compare/type.js
rename to lib/compare/type.js
index fb3a4dc..5f70d1c 100644
--- a/compare/type.js
+++ b/lib/compare/type.js
@@ -1,5 +1,5 @@
-import { getParams, getSymbol } from "../type_constructor.js";
-import { compareBools, compareSymbols } from "./primitives.js";
+import { getParams, getSymbol } from "../primitives/type.js";
+import { compareBools, compareNumbers, compareSymbols } from "./primitives.js";
 import { compareLists } from "./structures.js";
 
 const __compareTypes = state => typeX => typeY => {
@@ -20,7 +20,7 @@ const __compareTypes = state => typeX => typeY => {
                 // both sub-types have been visited already in an enclosing call
                 // if they were being compared in the same enclosing call, we assume they are equal!
                 // (we cannot compare them, that would result in endless recursion)
-                return compareSymbols(state.comparing.get(pX))(pY);
+                return compareNumbers(state.comparing.get(pX))(pY);
               }
               // none have been visited -> recursively compare
               return __compareTypes(state)(pX)(pY);
diff --git a/lib/compare/type.types.js b/lib/compare/type.types.js
new file mode 100644
index 0000000..ad11e3c
--- /dev/null
+++ b/lib/compare/type.types.js
@@ -0,0 +1,8 @@
+import { getDefaultTypeParser } from "../parser/type_parser.js";
+import { compareTypes } from "./type.js";
+
+const mkType = getDefaultTypeParser();
+
+export const ModuleCompareTypes = [
+  {i: compareTypes, t: mkType("Type -> Type -> Int")},
+];
diff --git a/compare/versioning.js b/lib/compare/versioning.js
similarity index 100%
rename from compare/versioning.js
rename to lib/compare/versioning.js
diff --git a/generics/generics.js b/lib/generics/generics.js
similarity index 93%
rename from generics/generics.js
rename to lib/generics/generics.js
index 1d8089a..d8ee7e4 100644
--- a/generics/generics.js
+++ b/lib/generics/generics.js
@@ -96,11 +96,11 @@ export const mergeTwoWay = (m1, m2) => {
 //   fType, aType: generic types to unify
 //   fStack, aStack: internal use.
 const __unify = (typeVars, fType, aType, fStack=[], aStack=[]) => {
-  // console.log("__unify", {typeVars, fType, aType, fStack, aStack});
+  // console.log("__unify", {typeVars, fType: prettyT(fType), aType: prettyT(aType), fStack, aStack});
   if (typeVars.has(fType)) {
     // simplest case: formalType is a type paramater
     //   => substitute with actualType
-    // console.log("assign actual to formal");
+    // console.log(`assign ${prettyT(aType)} to ${prettyT(fType)}`);
     return {
       substitutions: new Map([[fType, aType]]),
       genericType: {
@@ -111,7 +111,7 @@ const __unify = (typeVars, fType, aType, fStack=[], aStack=[]) => {
   }
   if (typeVars.has(aType)) {
     // same as above, but in the other direction
-    // console.log("assign formal to actual");
+    // console.log(`assign ${prettyT(fType)} to ${prettyT(aType)}`);
     return {
       substitutions: new Map([[aType, fType]]),
       genericType: {
@@ -163,7 +163,7 @@ const __unify = (typeVars, fType, aType, fStack=[], aStack=[]) => {
   };
 
   const [unifiedSubstitutions, unifiedTypeVars] = unifications.reduce((acc, getParam) => {
-    const self = Symbol();
+    const self = Symbol(); // dirty, just need something unique
     const {substitutions, deletions} = mergeTwoWay(acc[0], getParam(self).substitutions);
     return [substitutions, acc[1]
       .difference(substitutions)
@@ -206,8 +206,8 @@ export const assign = (genFnType, paramType) => {
   let allTypeVars;
   [allTypeVars, genFnType, paramType] = safeUnionTypeVars(genFnType, paramType);
   const [inType, outType] = genFnType.type.params;
-  const {substitutions} = unifyInternal(allTypeVars, inType, paramType.type);
-  const substitutedOutType = substitute(outType, substitutions);
+  const {substitutions} = __unify(allTypeVars, inType(genFnType.type), paramType.type);
+  const substitutedOutType = substitute(outType(genFnType.type), substitutions);
   return recomputeTypeVars(onlyOccurring(substitutedOutType, allTypeVars));
 };
 
@@ -215,7 +215,7 @@ export const assignFn = (genFnType, paramType) => {
   let allTypeVars;
   [allTypeVars, genFnType, paramType] = safeUnionTypeVars(genFnType, paramType);
   const [inType] = genFnType.type.params;
-  const {substitutions} = unifyInternal(allTypeVars, inType, paramType.type);
+  const {substitutions} = __unify(allTypeVars, inType, paramType.type);
   const substitutedFnType = substitute(genFnType.type, substitutions);
   return recomputeTypeVars(onlyOccurring(substitutedFnType, allTypeVars));
 };
diff --git a/lib/meta/type_constructor.js b/lib/meta/type_constructor.js
new file mode 100644
index 0000000..825f76a
--- /dev/null
+++ b/lib/meta/type_constructor.js
@@ -0,0 +1,21 @@
+import { getHumanReadableName } from "../primitives/symbol.js";
+
+const __makeTypeConstructor = (symbol, nAry, params) => {
+  if (nAry === 0) {
+    return { symbol, params };
+  }
+  // only for debugging, do we give the function a name
+  const fName = `${getHumanReadableName(symbol).toLowerCase()}Type${params.length>0?params.length:''}`;
+  return {
+    [fName]: typeParam => {
+      if (typeof typeParam !== 'function') {
+        throw new Error("all type params must be functions");
+      }
+      return __makeTypeConstructor(symbol, nAry-1, params.concat([typeParam]));
+    }
+  }[fName];
+}
+
+// Creates a new nominal type
+// export const makeTypeConstructor = symbol => nAry => makeTypeConstructorInternal(symbol, nAry);
+export const makeTypeConstructor = symbol => nAry => __makeTypeConstructor(symbol, nAry, []);
diff --git a/lib/meta/type_constructor.types.js b/lib/meta/type_constructor.types.js
new file mode 100644
index 0000000..ff13e94
--- /dev/null
+++ b/lib/meta/type_constructor.types.js
@@ -0,0 +1,9 @@
+import { getDefaultTypeParser } from "../parser/type_parser.js"
+import { makeTypeConstructor } from "./type_constructor.js";
+
+const mkType = getDefaultTypeParser();
+
+export const ModuleTypeConstructor = [
+  // Problem: number of parameters of returned function depends on the 'Int' parameter...
+  // {i: makeTypeConstructor, t: mkType("SymbolT -> Int -> ??")}
+];
diff --git a/lib/parser/type_parser.js b/lib/parser/type_parser.js
new file mode 100644
index 0000000..3ba9b07
--- /dev/null
+++ b/lib/parser/type_parser.js
@@ -0,0 +1,206 @@
+// A simple, hacked-together recursive parser for types.
+
+import { Bool, Char, Double, Int, SymbolT, Type, Unit } from "../primitives/primitive_types.js";
+import { Dynamic } from "../primitives/primitive_types.js";
+import { dictType, fnType, lsType, prodType, sumType } from "../structures/type_constructors.js";
+import { setType } from "../structures/type_constructors.js";
+
+export const makeTypeParser = ({
+  // parser can be extended:
+  extraPrimitives=[],
+  extraBracketOperators=[],
+  extraInfixOperators=[],
+}) => {
+  const a = Symbol('a');
+  const b = Symbol('b');
+  const c = Symbol('c');
+  const d = Symbol('d');
+  const e = Symbol('e');
+  
+  const primitives = new Map([
+    ['Int', Int],
+    ['Double', Double],
+    ['Bool', Bool],
+    ['Char', Char],
+    ['String', lsType(_ => Char)],
+    ['Module', lsType(_ => Dynamic)],
+    ['Unit', Unit],
+    ['Type', Type],
+    ['Dynamic', Dynamic],
+    ['SymbolT', SymbolT],
+    ['a', a],
+    ['b', b],
+    ['c', c],
+    ['d', d],
+    ['e', e],
+
+    ...extraPrimitives,
+  ]);
+
+  const bracketOperators = new Map([
+    ['(', [')', null]],
+    ['[', [']', lsType]],
+    ['{', ['}', setType]],
+  
+    // can only occur at beginning
+    // we use these to extract the type variables
+    ['∀', [':', null]],
+  
+    ...extraBracketOperators,
+  ]);
+  
+  const infixOperators = new Map([
+    ['+', sumType],
+    ['|', sumType],
+    ['⨯', prodType],
+    ['*', prodType],
+    ['→', fnType],
+    ['->', fnType],
+    ['⇒', dictType],
+    ['=>', dictType],
+  
+    // only used for type variables (e.g., ∀a,b,c:)
+    [',', fnX => fnY => {
+      const x = fnX();
+      const y = fnY();
+      return Array.isArray(x) ? x.concat(y) : [x].concat(y)
+    }],
+
+    ...extraInfixOperators,
+  ]);
+  
+  
+  const TOKENS = [
+    ...bracketOperators.keys(),
+    ...[...bracketOperators.values()].map(v => v[0]),
+    ...infixOperators.keys(),
+    ...primitives.keys(),
+  ].toSorted((a,b) => {
+    return (b.length - a.length); // try longer tokens first
+  });
+  
+  // console.log('TOKENS =', TOKENS);
+  
+  const tokenize = expr => {
+    const tokens = [];
+    let i=0;
+    outerloop: while (i<expr.length) {
+      if (/\s/.test(expr[i])) {
+        i++;
+        continue outerloop; // skip whitespace
+      }
+      if (expr[i] === '#') {
+        const label = '#' + parseInt(expr.slice(i+1));
+        tokens.push(label);
+        i += label.length;
+        continue outerloop;
+      }
+      for (const token of TOKENS) {
+        if (expr.startsWith(token, i)) {
+          tokens.push(token);
+          i += token.length;
+          continue outerloop;
+        }
+      }
+      throw new Error(`Couldn't match any token at position ${i} in\n  ${expr}\n  ${' '.repeat(i)}^`);
+    }
+    // console.log({tokens});
+    return tokens;
+  }
+  
+  const consumeGroup = (tokens) => {
+    const bracket = bracketOperators.get(tokens[0]);
+    if (bracket === undefined) {
+      // no group, just a single token:
+      const [firstToken, ...rest] = tokens;
+      return [[firstToken], null, rest];
+    }
+    else {
+      // find where group ends:
+      const [closing, fn] = bracket;
+      const opening = tokens[0]
+      let depth = 1;
+      let i = 1;
+      for (; i<tokens.length; i++) {
+        if (tokens[i] === opening) {
+          depth++;
+        }
+        else if (tokens[i] === closing) {
+          depth--;
+        }
+        if (depth === 0) {
+          break;
+        }
+      }
+      const tokensInGroup = tokens.slice(1, i); // don't include brackets
+      const rest = tokens.slice(i+1);
+      return [tokensInGroup, fn, rest];
+    }
+  }
+  
+  const parseGroup = (tokensInGroup, fn, labels, label) => {
+    // console.log('parseGroup ', tokensInGroup, fn);
+    return (fn === null)
+      ? __parse(tokensInGroup, labels, label)
+      : fn(self => {
+          return __parse(tokensInGroup, extendLabels(labels, label, self));
+        });
+  }
+  
+  const extendLabels = (labels, label, self) => {
+    return (label === null) ? labels : new Map([...labels, [label, self]])
+  };
+  
+  const __parse = (tokens, labels = new Map(), label = null) => {
+    // console.log('parse ', tokens);
+    if (tokens[0].startsWith('#')) {
+      if (labels.has(tokens[0])) {
+        return labels.get(tokens[0]);
+      }
+      else {
+        // pass label and parse 'rest'
+        return __parse(tokens.slice(1), labels, tokens[0]);
+      }
+    }
+    if (tokens.length === 1) {
+      return primitives.get(tokens[0]);
+    }
+    else {
+      const [lhsTokens, fnGrp, rest] = consumeGroup(tokens);
+      if (rest.length === 0) {
+        return parseGroup(lhsTokens, fnGrp, labels, label);
+      }
+      const [operator, ...rhsTokens] = rest;
+      for (const [operatorChar, fn] of infixOperators) {
+        if (operator === operatorChar) {
+          return fn
+            (self => {
+              return parseGroup(lhsTokens, fnGrp, extendLabels(labels, label, self));
+            })(self => {
+              return __parse(rhsTokens, extendLabels(labels, label, self));
+            });
+        }
+      }
+      throw new Error("unknown operator: "+operator)
+    }
+  };
+  
+  const parse = expr => {
+    const tokens = tokenize(expr);
+    if (tokens[0] === '∀') {
+      // generic type
+      const [typeVarTokens, _, rest] = consumeGroup(tokens);
+      const typeVars = [].concat(__parse(typeVarTokens))
+      const type = __parse(rest);
+      return { typeVars, type };
+    }
+    return __parse(tokens);
+  }
+
+  return parse;
+}
+
+let defaultParser;
+export const getDefaultTypeParser = () => {
+  return defaultParser || (defaultParser = makeTypeParser({}));
+};
diff --git a/lib/point.js b/lib/point.js
deleted file mode 100644
index cb116cb..0000000
--- a/lib/point.js
+++ /dev/null
@@ -1,73 +0,0 @@
-import { Type } from "../primitives/types.js";
-import { typedFnType } from "../structures/types.js"
-import { Double } from "../primitives/types.js";
-import { makeTypeConstructor } from "../type_constructor.js";
-
-// Create nominal types
-export const PointCartesian2D = makeTypeConstructor(Symbol('PointCartesian2D'))(0);
-export const PointPolar2D     = makeTypeConstructor(Symbol('PointPolar2D'))(0);
-
-export const cart2polar = ({x, y}) => {
-  const r = Math.sqrt(x*x + y*y);
-  const θ = Math.atan(y/x);
-  return {r, θ};
-};
-
-export const polar2cart = ({r, θ}) => {
-  const x = r * Math.cos(θ);
-  const y = r * Math.sin(θ);
-  return {x, y};
-}
-
-export const translate = dx => dy => ({x, y}) => {
-  return {left: x+dx, right: y+dy};
-}
-
-export const rotate = dθ => ({r, θ}) => {
-  return {r, θ: θ+dθ};
-}
-
-export const scale = dr => ({r, θ}) => {
-  return {r: r+dr, θ};
-}
-
-const examplePoint = {x: 1, y: 2};
-
-export const ModulePoint = {l:[
-  {i: -1                 , t: Double},
-  {i: 2                  , t: Double},
-  {i: examplePoint       , t: PointCartesian2D},
-
-  {i: PointCartesian2D   , t: Type},
-  {i: PointPolar2D       , t: Type},
-
-  ...typedFnType(cart2polar, fnType => fnType(() => PointCartesian2D)(() => PointPolar2D)),
-
-  ...typedFnType(polar2cart, fnType => fnType(() => PointPolar2D)(() => PointCartesian2D)),
-
-  // Double -> Double -> PointCartesian2D -> PointCartesian2D
-  ...typedFnType(translate, fnType =>
-    fnType
-      (Double)
-      (fnType
-        (Double)
-        (fnType
-          (PointCartesian2D)
-          (PointCartesian2D)))),
-
-  // Double -> PointPolar2D -> PointPolar2D
-  ...typedFnType(rotate, fnType =>
-    fnType
-      (Double)
-      (fnType
-        (PointPolar2D)
-        (PointPolar2D))),
-
-  // Double -> PointPolar2D -> PointPolar2D
-  ...typedFnType(scale, fnType =>
-    fnType
-      (Double)
-      (fnType
-        (PointPolar2D)
-        (PointPolar2D))),
-]};
diff --git a/lib/point_structural.js b/lib/point_structural.js
deleted file mode 100644
index d530c82..0000000
--- a/lib/point_structural.js
+++ /dev/null
@@ -1,140 +0,0 @@
-import { prettyT, typedFnType } from "../structures/types.js"
-import { Double } from "../primitives/types.js";
-import { makeConstructor, makeConstructorType, makeGetters, makeGettersTypes, structType } from "../structures/struct.js";
-import { newProduct } from "../structures/product.js";
-import { makeTypeConstructor } from "../type_constructor.js";
-
-const cartFields = [
-  newProduct("x")(Double),
-  newProduct("y")(Double),
-];
-
-const polarFields = [
-  newProduct("r")(Double),
-  newProduct("θ")(Double),
-];
-
-// Nominal types:
-export const NPoint2DCartesian = makeTypeConstructor(Symbol('Point2DCartesian'))(0);
-export const NPoint2DPolar     = makeTypeConstructor(Symbol('Point2DPolar'))(0);
-
-// Structural types:
-export const SPoint2DCartesian = structType(cartFields);  // (Double, (Double, Unit))
-export const SPoint2DPolar     = structType(polarFields); // (Double, (Double, Unit))
-
-export const constructorPoint2DCartesian = makeConstructor(cartFields);
-export const constructorPoint2DPolar     = makeConstructor(polarFields);
-
-export const constructorPoint2DCartesianFnType = makeConstructorType(NPoint2DCartesian)(cartFields);
-export const constructorPoint2DPolarFnType     = makeConstructorType(NPoint2DPolar)(polarFields);
-
-export const [getX, getY] = makeGetters(cartFields);
-export const [getR, getΘ] = makeGetters(polarFields);
-
-export const [getXFnType, getYFnType] = makeGettersTypes(NPoint2DCartesian)(cartFields);
-export const [getRFnType, getΘFnType] = makeGettersTypes(NPoint2DPolar)(polarFields);
-
-export const cart2polar = cart => {
-  const x = getX(cart);
-  const y = getY(cart);
-  const r = Math.sqrt(x*x + y*y);
-  const θ = Math.atan(y/x);
-  return constructorPoint2DPolar(r)(θ);
-};
-
-export const polar2cart = polar => {
-  const r = getR(polar);
-  const θ = getΘ(polar);
-  const x = r * Math.cos(θ);
-  const y = r * Math.sin(θ);
-  return constructorPoint2DCartesian(x)(y);
-};
-
-export const cart2Str = cart => {
-  const x = getX(cart);
-  const y = getY(cart);
-  return {l: `{x: ${x}, y: ${y}}`};
-};
-
-export const polar2Str = polar => {
-  const r = getR(polar);
-  const θ = getΘ(polar);
-  return {l: `{r: ${r}, θ: ${θ}}`};
-};
-
-// export const translate = dx => dy => ({x, y}) => {
-//   return {x: x+dx, y: y+dy};
-// };
-
-// export const rotate = dθ => ({r, θ}) => {
-//   return {r, θ: θ+dθ};
-// };
-
-// export const scale = dr => ({r, θ}) => {
-//   return {r: r+dr, θ};
-// };
-
-// const examplePoint = {x: 1, y: 2};
-
-const examplePointCart = constructorPoint2DCartesian(1)(2);
-const examplePointPolar = constructorPoint2DCartesian(0)(5);
-
-console.log(prettyT(getXFnType));
-
-export const ModulePoint = {l:[
-  // {i: -1                 , t: Double},
-  // {i: 2                  , t: Double},
-  // {i: examplePoint       , t: Point2DCartesian},
-
-  {i: examplePointCart, t: SPoint2DCartesian},
-  {i: examplePointCart, t: NPoint2DCartesian},
-
-  {i: examplePointPolar, t: SPoint2DPolar},
-  {i: examplePointPolar, t: NPoint2DPolar},
-
-  // {i: SPoint2DCartesian   , t: Type},
-  // {i: SPoint2DPolar       , t: Type},
-
-  // {i: NPoint2DCartesian   , t: Type},
-  // {i: NPoint2DPolar       , t: Type},
-
-  {i: getX, t: getXFnType},
-  {i: getY, t: getYFnType},
-  {i: getR, t: getRFnType},
-  {i: getΘ, t: getΘFnType},
-
-  ...typedFnType(cart2polar, fnType => fnType(() => NPoint2DCartesian)(() => NPoint2DPolar)),
-  ...typedFnType(polar2cart, fnType => fnType(() => NPoint2DPolar)(() => NPoint2DCartesian)),
-
-  // ...typedFnType(polar2cart, fnType => fnType(() => Point2DPolar)(() => Point2DCartesian)),
-
-  // // Double -> Double -> PointCartesian2D -> PointCartesian2D
-  // ...typedFnType(translate, fnType =>
-  //   fnType
-  //     (Double)
-  //     (fnType
-  //       (Double)
-  //       (fnType
-  //         (Point2DCartesian)
-  //         (Point2DCartesian)))),
-
-  // ...typedFnType(cart2tuple, fnType => fnType(() => Point2DCartesian)(prodType(() => Double)(() => () => Double))),
-  
-  // ...typedFnType(polar2tuple, fnType => fnType(() => Point2DPolar)(prodType(() => Double)(() => () => Double))),
-
-  // // Double -> PointPolar2D -> PointPolar2D
-  // ...typedFnType(rotate, fnType =>
-  //   fnType
-  //     (Double)
-  //     (fnType
-  //       (Point2DPolar)
-  //       (Point2DPolar))),
-
-  // // Double -> PointPolar2D -> PointPolar2D
-  // ...typedFnType(scale, fnType =>
-  //   fnType
-  //     (Double)
-  //     (fnType
-  //       (Point2DPolar)
-  //       (Point2DPolar))),
-]};
diff --git a/lib/primitives/double.js b/lib/primitives/double.js
new file mode 100644
index 0000000..281e815
--- /dev/null
+++ b/lib/primitives/double.js
@@ -0,0 +1,3 @@
+export const addDouble = x => y => x + y;
+export const mulDouble = x => y => x * y;
+export const eqDouble  = x => y => x === y;
diff --git a/lib/primitives/double.types.js b/lib/primitives/double.types.js
new file mode 100644
index 0000000..6e64769
--- /dev/null
+++ b/lib/primitives/double.types.js
@@ -0,0 +1,10 @@
+import { getDefaultTypeParser } from "../parser/type_parser.js";
+import { addDouble, eqDouble, mulDouble } from "./double.js";
+
+const mkType = getDefaultTypeParser();
+
+export const ModuleDouble = [
+  { i: addDouble, t: mkType("Double -> Double -> Double") },
+  { i: mulDouble, t: mkType("Double -> Double -> Double") },
+  { i: eqDouble, t: mkType("Double -> Double -> Bool") },
+];
diff --git a/lib/primitives/dynamic.js b/lib/primitives/dynamic.js
new file mode 100644
index 0000000..6f01125
--- /dev/null
+++ b/lib/primitives/dynamic.js
@@ -0,0 +1,3 @@
+export const newDynamic = i => t => ({i, t});
+export const getInst = lnk => lnk.i;
+export const getType = lnk => lnk.t;
diff --git a/lib/primitives/dynamic.types.js b/lib/primitives/dynamic.types.js
new file mode 100644
index 0000000..1cf645a
--- /dev/null
+++ b/lib/primitives/dynamic.types.js
@@ -0,0 +1,14 @@
+import { getDefaultTypeParser } from "../parser/type_parser.js";
+import { getInst, getType, newDynamic } from "./dynamic.js";
+
+const mkType = getDefaultTypeParser();
+
+export const ModuleDynamic = [
+  { i: newDynamic, t: mkType("∀a: a -> Type -> Dynamic")},
+
+  // allows us to (unsafely) cast the result to the specific type...
+  // (not sure if this is the right way to go)
+  { i: getInst, t: mkType("∀a: Dynamic -> a") },
+
+  { i: getType, t: mkType("Dynamic -> Type") },
+];
diff --git a/lib/primitives/int.js b/lib/primitives/int.js
new file mode 100644
index 0000000..ef9e19d
--- /dev/null
+++ b/lib/primitives/int.js
@@ -0,0 +1,3 @@
+export const addInt = x => y => x + y;
+export const mulInt = x => y => x * y;
+export const eqInt  = x => y => x === y;
diff --git a/lib/primitives/int.types.js b/lib/primitives/int.types.js
new file mode 100644
index 0000000..dd3a2b8
--- /dev/null
+++ b/lib/primitives/int.types.js
@@ -0,0 +1,10 @@
+import { getDefaultTypeParser }from "../parser/type_parser.js";
+import { addInt, eqInt, mulInt } from "./int.js";
+
+const mkType = getDefaultTypeParser();
+
+export const ModuleInt = [
+  { i: addInt, t: mkType("Int -> Int -> Int") },
+  { i: mulInt, t: mkType("Int -> Int -> Int") },
+  { i: eqInt, t: mkType("Int -> Int -> Bool") },
+];
diff --git a/lib/primitives/primitive_types.js b/lib/primitives/primitive_types.js
new file mode 100644
index 0000000..c4b7f88
--- /dev/null
+++ b/lib/primitives/primitive_types.js
@@ -0,0 +1,40 @@
+// to break up dependency cycles, primitive types are defined in their own JS module
+
+import { makeTypeConstructor } from "../meta/type_constructor.js";
+
+export const SymbolInt         = "Int__02a884563f7d480bb14c09be640dfe7a";
+export const SymbolBool        = "Bool__d64c4865bead40439dad62727aaaac2d";
+export const SymbolDouble      = "Double__be70f3c8f53f4419a7866d106faae091";
+export const SymbolByte        = "Byte__bf9e8453cd554e81971880ba33dc9f27";
+export const SymbolChar        = "Char__e47159519d3345119336b751fc8da1de";
+export const SymbolUnit        = "Unit__a70ca021c32a4036a594d332aedfb029";
+export const SymbolBottom      = "⊥__95beece951bc457781be8c5481d35dcc";
+export const SymbolSymbol      = "Symbol__f67c077430e04e4fa40ed2e2b2a3040d";
+export const SymbolType        = "Type__fdbea309d66f49b483b0dd4ceb785f7d";
+export const SymbolTop         = "⊤__38709c3c0039468782103256d4730d1f";
+export const SymbolGenericType = "GenericType__e9d8010b82f64206afa83d0c163df5d2";
+export const SymbolDynamic     = "Dynamic__3c16c415dba94228ada37dc9d446f54f";
+
+export const Int     = makeTypeConstructor(SymbolInt)(0);
+export const Bool    = makeTypeConstructor(SymbolBool)(0);
+export const Double  = makeTypeConstructor(SymbolDouble)(0);
+export const Byte    = makeTypeConstructor(SymbolByte)(0);
+export const Char    = makeTypeConstructor(SymbolChar)(0);
+
+// Unit type has only 1 instance, the empty tuple.
+export const Unit    = makeTypeConstructor(SymbolUnit)(0);
+
+// Bottom type has no instances.
+export const Bottom  = makeTypeConstructor(SymbolBottom)(0);
+
+export const SymbolT = makeTypeConstructor(SymbolSymbol)(0);
+
+// Types are typed by Top
+export const Type    = makeTypeConstructor(SymbolType)(0);
+
+export const GenericType = makeTypeConstructor(SymbolGenericType)(0);
+
+// Everything is typed by Top
+export const Top = makeTypeConstructor(SymbolTop)(0);// A type-link, connecting a value to its Type.
+
+export const Dynamic = makeTypeConstructor(SymbolDynamic)(0);
diff --git a/lib/primitives/primitive_types.types.js b/lib/primitives/primitive_types.types.js
new file mode 100644
index 0000000..c5a49d1
--- /dev/null
+++ b/lib/primitives/primitive_types.types.js
@@ -0,0 +1,31 @@
+import { SymbolInt, SymbolT, SymbolBool, SymbolDouble, SymbolByte, SymbolChar, SymbolUnit, SymbolBottom, SymbolSymbol, SymbolType, SymbolGenericType, SymbolTop, Type, Int, Bool, Double, Byte, Char, Unit, Bottom, GenericType, Top, SymbolDynamic, Dynamic } from "./primitive_types.js";
+
+export const ModulePrimitiveSymbols = [
+  { i: SymbolInt         , t: SymbolT },
+  { i: SymbolBool        , t: SymbolT },
+  { i: SymbolDouble      , t: SymbolT },
+  { i: SymbolByte        , t: SymbolT },
+  { i: SymbolChar        , t: SymbolT },
+  { i: SymbolUnit        , t: SymbolT },
+  { i: SymbolBottom      , t: SymbolT },
+  { i: SymbolSymbol      , t: SymbolT },
+  { i: SymbolType        , t: SymbolT },
+  { i: SymbolGenericType , t: SymbolT },
+  { i: SymbolTop         , t: SymbolT },
+  { i: SymbolDynamic     , t: SymbolT },
+];
+
+export const ModulePrimitiveTypes = [
+  { i: Int         , t: Type },
+  { i: Bool        , t: Type },
+  { i: Double      , t: Type },
+  { i: Byte        , t: Type },
+  { i: Char        , t: Type },
+  { i: Unit        , t: Type },
+  { i: Bottom      , t: Type },
+  { i: SymbolT     , t: Type },
+  { i: Type        , t: Type },
+  { i: GenericType , t: Type },
+  { i: Top         , t: Type },
+  { i: Dynamic     , t: Type },
+];
diff --git a/lib/primitives/symbol.js b/lib/primitives/symbol.js
new file mode 100644
index 0000000..06444a8
--- /dev/null
+++ b/lib/primitives/symbol.js
@@ -0,0 +1,2 @@
+export const getHumanReadableName = symbol => symbol.slice(0, -34); // drop UUID
+export const eqSymbol = a => b => a === b;
diff --git a/lib/primitives/symbol.types.js b/lib/primitives/symbol.types.js
new file mode 100644
index 0000000..04f74a3
--- /dev/null
+++ b/lib/primitives/symbol.types.js
@@ -0,0 +1,9 @@
+import { getDefaultTypeParser } from "../parser/type_parser.js"
+import { eqSymbol, getHumanReadableName } from "./symbol.js";
+
+const mkType = getDefaultTypeParser();
+
+export const ModuleSymbol = [
+  { i: getHumanReadableName, t: mkType("SymbolT -> String")},
+  { i: eqSymbol, t: mkType("SymbolT -> SymbolT -> Bool")},
+];
diff --git a/lib/primitives/type.js b/lib/primitives/type.js
new file mode 100644
index 0000000..ad30b9d
--- /dev/null
+++ b/lib/primitives/type.js
@@ -0,0 +1,6 @@
+import { compareTypes } from "../compare/type.js";
+
+export const getSymbol = type => type.symbol;
+export const getParams = type => type.params;
+
+export const eqType = t1 => t2 => compareTypes(t1, t2) === 0;
diff --git a/lib/primitives/type.types.js b/lib/primitives/type.types.js
new file mode 100644
index 0000000..52992a0
--- /dev/null
+++ b/lib/primitives/type.types.js
@@ -0,0 +1,13 @@
+// a module is just a set of typed objects
+
+import { getDefaultTypeParser } from "../parser/type_parser.js";
+import { eqType, getParams, getSymbol } from "./type.js";
+
+const mkType = getDefaultTypeParser();
+
+// each 'typed object' is implicitly an instance of TypeLink (defined below)
+export const ModuleType = [
+  {i: eqType   , t: mkType("Type -> Type -> Bool")},
+  {i: getSymbol, t: mkType("Type -> SymbolT")},
+  {i: getParams, t: mkType("Type -> [Type -> Type]")},
+];
diff --git a/lib/primitives/unit.js b/lib/primitives/unit.js
new file mode 100644
index 0000000..b4634e7
--- /dev/null
+++ b/lib/primitives/unit.js
@@ -0,0 +1,3 @@
+export const unit = {};
+
+export const eqUnit = _ => _ => true;
diff --git a/lib/primitives/unit.types.js b/lib/primitives/unit.types.js
new file mode 100644
index 0000000..33f64e5
--- /dev/null
+++ b/lib/primitives/unit.types.js
@@ -0,0 +1,9 @@
+import { getDefaultTypeParser } from "../parser/type_parser.js";
+import { eqUnit, unit } from "./unit.js";
+
+const mkType = getDefaultTypeParser();
+
+export const ModuleUnit = [
+  {i: unit  , t: mkType("Unit")},
+  {i: eqUnit, t: mkType("Unit -> Unit -> Bool")},
+];
diff --git a/lib/stdlib.js b/lib/stdlib.js
new file mode 100644
index 0000000..8c85332
--- /dev/null
+++ b/lib/stdlib.js
@@ -0,0 +1,48 @@
+import { ModuleDouble } from "./primitives/double.types.js";
+import { ModuleDynamic } from "./primitives/dynamic.types.js";
+import { ModuleInt } from "./primitives/int.types.js";
+import { ModulePrimitiveSymbols, ModulePrimitiveTypes } from "./primitives/primitive_types.types.js";
+import { ModuleSymbol } from "./primitives/symbol.types.js";
+import { ModuleType } from "./primitives/type.types.js";
+import { ModuleUnit } from "./primitives/unit.types.js";
+
+import { ModuleDict } from "./structures/dict.types.js"
+import { ModuleList } from "./structures/list.types.js"
+import { ModuleProduct } from "./structures/product.types.js"
+import { ModuleSet } from "./structures/set.types.js"
+import { ModuleSum } from "./structures/sum.types.js"
+import { ModuleStructuralSymbols, ModuleTypeConstructors } from "./structures/type_constructors.types.js";
+
+import { ModuleCompareTypes } from "./compare/type.types.js";
+import { ModuleComparePrimitives } from "./compare/primitives.types.js";
+import { ModuleCompareStructures } from "./compare/structures.types.js";
+
+export const ModuleStd = [
+  // Symbols (for nominal types)
+  ...ModulePrimitiveSymbols,
+  ...ModuleStructuralSymbols,
+
+  // Nominal types
+  ...ModulePrimitiveTypes,
+  ...ModuleTypeConstructors,
+
+  // Operations on Primitives
+  ...ModuleDouble,
+  ...ModuleDynamic,
+  ...ModuleInt,
+  ...ModuleSymbol,
+  ...ModuleType,
+  ...ModuleUnit,
+
+  // Operations on Structures
+  ...ModuleDict,
+  ...ModuleList,
+  ...ModuleProduct,
+  ...ModuleSet,
+  ...ModuleSum,
+
+  // Comparison
+  ...ModuleCompareTypes,
+  ...ModuleComparePrimitives,
+  ...ModuleCompareStructures,
+];
diff --git a/lib/structures/dict.js b/lib/structures/dict.js
new file mode 100644
index 0000000..a5cc1cc
--- /dev/null
+++ b/lib/structures/dict.js
@@ -0,0 +1,22 @@
+import { RBTreeWrapper } from "../util/rbtree_wrapper.js";
+import { newProduct } from "./product.js";
+import { newLeft, newRight } from "./sum.js";
+
+export const emptyDict = compareFn => RBTreeWrapper.new((x, y) => compareFn(x)(y));
+
+export const has = dict => key => dict.tree.get(key) === true;
+export const set = dict => key => value => new RBTreeWrapper(dict.tree.remove(key).insert(key, value));
+export const remove = dict => key => new RBTreeWrapper(dict.tree.remove(key));
+export const length = dict => dict.tree.length;
+
+export const first = dict => dict.tree.begin;
+export const last  = dict => dict.tree.end;
+
+export const read = iter => {
+  if (iter !== undefined && iter.valid) {
+    return newRight(newProduct(newProduct(iter.key)(iter.value))(iter.clone().next()));
+  }
+  else {
+    return newLeft(unit);
+  }
+};
diff --git a/lib/structures/dict.types.js b/lib/structures/dict.types.js
new file mode 100644
index 0000000..3b2e7bc
--- /dev/null
+++ b/lib/structures/dict.types.js
@@ -0,0 +1,20 @@
+import { makeTypeParser } from "../parser/type_parser.js";
+import { makeTypeConstructor } from "../meta/type_constructor.js";
+import { emptyDict, first, has, last, length, read, remove, set } from "./dict.js";
+
+const dictIterator = makeTypeConstructor('DictIterator__d9d175b6bfd1283f00851a99787d0499')(2);
+
+const mkType = makeTypeParser({
+  extraInfixOperators: [['|=>|', dictIterator]],
+});
+
+export const ModuleDict = [
+  { i: emptyDict   , t: mkType("∀a,b: (a -> a -> Int) -> (a => b)") },
+  { i: has         , t: mkType("∀a,b: (a => b) -> a -> Bool")},
+  { i: set         , t: mkType("∀a,b: (a => b) -> a -> b -> (a => b)")},
+  { i: remove      , t: mkType("∀a,b: (a => b) -> a -> (a => b)")},
+  { i: length      , t: mkType("∀a,b: (a => b) -> Int")},
+  { i: first       , t: mkType("∀a,b: (a => b) -> (a |=>| b)")},
+  { i: last        , t: mkType("∀a,b: (a => b) -> (a |=>| b)")},
+  { i: read        , t: mkType("∀a,b: (a |=>| b) -> (Unit + ((a*b) * (a |=>| b)))")},
+];
diff --git a/structures/enum.js b/lib/structures/enum.js
similarity index 57%
rename from structures/enum.js
rename to lib/structures/enum.js
index 40f1ca7..cfc6e3c 100644
--- a/structures/enum.js
+++ b/lib/structures/enum.js
@@ -1,24 +1,6 @@
-import { Bottom } from "../primitives/types.js";
 import { capitalizeFirstLetter } from "../util/util.js";
-import { newProduct as newProduct, getLeft, getRight } from "./product.js";
+import { newProduct as newProduct, getLeft } from "./product.js";
 import { newLeft, newRight, match } from "./sum.js";
-import { sumType } from "./types.js";
-
-// 'variants' is an array of (name: string, type: Type) pairs.
-// e.g., the list of variants:
-//   [ { l: "price"    , r: Int   },
-//     { l: "prices"   , r: [Int] },
-//     { l: "not_found", r: Unit  }  ]
-// results in the type:
-//   (Int | ([Int] | (Unit | ⊥)))
-export const enumType = variants => {
-  if (variants.length === 0) {
-    return Bottom; // empty enum is equal to Bottom-type (cannot be instantiated)
-  }
-  const [variant, ...rest] = variants;
-  const variantType = getRight(variant);
-  return sumType(() => variantType)(() => enumType(rest));
-};
 
 const eatParameters = (numParams, result) => {
   if (numParams === 0) {
@@ -33,11 +15,9 @@ export const makeMatchFn = variants => {
   }
   const [_, ...remainingVariants] = variants;
   return sum => handler => {
-    return (
-      match(sum)(newProduct
+    return match(sum)
         (leftValue => eatParameters(remainingVariants.length, handler(leftValue)))
-        (rightValue => makeMatchFn(remainingVariants)(rightValue))
-      ));
+        (rightValue => makeMatchFn(remainingVariants)(rightValue));
   };
 };
 
diff --git a/lib/structures/enum.types.js b/lib/structures/enum.types.js
new file mode 100644
index 0000000..21436d9
--- /dev/null
+++ b/lib/structures/enum.types.js
@@ -0,0 +1,20 @@
+import { Bottom } from "../primitives/primitive_types.js";
+import { getRight } from "./product.js";
+import { sumType } from "./type_constructors.js";
+
+// 'variants' is an array of (name: string, type: Type) pairs.
+// e.g., the list of variants:
+//   [ { l: "price"    , r: Int   },
+//     { l: "prices"   , r: [Int] },
+//     { l: "not_found", r: Unit  }  ]
+// results in the type:
+//   (Int | ([Int] | (Unit | ⊥)))
+
+export const enumType = variants => {
+  if (variants.length === 0) {
+    return Bottom; // empty enum is equal to Bottom-type (cannot be instantiated)
+  }
+  const [variant, ...rest] = variants;
+  const variantType = getRight(variant);
+  return sumType(() => variantType)(() => enumType(rest));
+};
diff --git a/lib/structures/list.js b/lib/structures/list.js
new file mode 100644
index 0000000..884a6da
--- /dev/null
+++ b/lib/structures/list.js
@@ -0,0 +1,16 @@
+// 'normal' implementation
+export const emptyList = [];
+// const emptyListType = makeGeneric(a => lsType(() => a));
+export const get = ls => i => ls[i];
+export const put = ls => i => elem => ls.with(Number(i), elem);
+export const push = ls => elem => ls.concat([elem]);
+export const pop = ls => ls.pop();
+export const map = ls => fn => ls.map(elem => fn(elem));
+export const length = ls => ls.length;
+export const fold = ls => callback => initial => {
+  let acc = initial;
+  for (let i=0; i<ls.length; i++) {
+    acc = callback(acc)(ls[i]);
+  }
+  return acc;
+}
diff --git a/lib/structures/list.types.js b/lib/structures/list.types.js
new file mode 100644
index 0000000..b3fa8f3
--- /dev/null
+++ b/lib/structures/list.types.js
@@ -0,0 +1,15 @@
+import { getDefaultTypeParser }from "../parser/type_parser.js";
+import { emptyList, fold, get, length, map, pop, push, put } from "./list.js";
+
+const mkType = getDefaultTypeParser();
+
+export const ModuleList = [
+  { i: emptyList, t: mkType("∀a: [a]")},
+  { i: get      , t: mkType("∀a: [a] -> Int -> a")},
+  { i: put      , t: mkType("∀a: [a] -> Int -> a -> [a]")},
+  { i: push     , t: mkType("∀a: [a] -> a -> [a]")},
+  { i: pop      , t: mkType("∀a: [a] -> a")},
+  { i: map      , t: mkType("∀a: [a] -> (a -> b) -> [b]")},
+  { i: length   , t: mkType("∀a: [a] -> Int")},
+  { i: fold     , t: mkType("∀a: [a] -> (b -> a -> b) -> b -> b")},
+];
diff --git a/structures/product.js b/lib/structures/product.js
similarity index 99%
rename from structures/product.js
rename to lib/structures/product.js
index 64548db..e39c444 100644
--- a/structures/product.js
+++ b/lib/structures/product.js
@@ -3,7 +3,6 @@
 // A Product-type always has only two fields, called "left" and "right".
 // Product-types of more fields (called Structs) can be constructed by nesting Product-types.
 
-
 // In JS, all products are encoded in the same way:
 export const newProduct = l => r => ({l, r});
 export const getLeft     = product => product.l;
diff --git a/lib/structures/product.types.js b/lib/structures/product.types.js
new file mode 100644
index 0000000..47b3c13
--- /dev/null
+++ b/lib/structures/product.types.js
@@ -0,0 +1,10 @@
+import { getDefaultTypeParser } from "../parser/type_parser.js";
+import { newProduct, getLeft, getRight } from "./product.js";
+
+const mkType = getDefaultTypeParser();
+
+export const ModuleProduct = [
+  { i: newProduct, t: mkType("∀a,b: a -> b -> (a * b)") },
+  { i: getLeft   , t: mkType("∀a,b: (a * b) -> a"     ) },
+  { i: getRight  , t: mkType("∀a,b: (a * b) -> b"     ) },
+];
diff --git a/lib/structures/set.js b/lib/structures/set.js
new file mode 100644
index 0000000..e2257f0
--- /dev/null
+++ b/lib/structures/set.js
@@ -0,0 +1,29 @@
+import { newRight } from "./sum.js";
+import { newProduct } from "./product.js";
+import { unit } from "../primitives/unit.js";
+import { RBTreeWrapper } from "../util/rbtree_wrapper.js";
+
+// (a -> a -> Int) -> Set(a)
+export const emptySet = compareFn => RBTreeWrapper.new((x, y) => compareFn(x)(y));
+
+export const has = set => key => set.tree.get(key) === true;
+export const add = set => key => set.tree.get(key) === true ? set : new RBTreeWrapper(set.tree.insert(key, true));
+export const remove = set => key => new RBTreeWrapper(set.tree.remove(key));
+export const length = set => set.tree.length;
+
+export const first = set => set.tree.begin;
+export const last  = set => set.tree.end;
+
+// test if iterator is 'done', and if not, get element and advance iterator.
+export const read = iter => {
+  if (iter !== undefined && iter.valid) {
+    return newRight(newProduct(iter.key)(iter.clone().next()));
+  }
+  else {
+    return newLeft(unit);
+  }
+};
+
+export const forEach = set => fn => {
+  set.tree.forEach(key => { fn(key); });
+};
diff --git a/lib/structures/set.types.js b/lib/structures/set.types.js
new file mode 100644
index 0000000..20e39da
--- /dev/null
+++ b/lib/structures/set.types.js
@@ -0,0 +1,20 @@
+import { makeTypeParser } from "../parser/type_parser.js";
+import { makeTypeConstructor } from "../meta/type_constructor.js";
+import { emptySet, has, add, remove, length, first, read, last } from "./set.js";
+
+const setIterator = makeTypeConstructor('SetIterator__f6b0ddd78ed41c58e5a442f2681da011')(1);
+
+const mkType = makeTypeParser({
+  extraBracketOperators: [['<', ['>', setIterator]]],
+});
+
+export const ModuleSet = [
+  { i: emptySet    , t: mkType("∀a: (a -> a -> Int) -> {a}") },
+  { i: has         , t: mkType("∀a: {a} -> a -> Bool")},
+  { i: add         , t: mkType("∀a: {a} -> a -> {a}")},
+  { i: remove      , t: mkType("∀a: {a} -> a -> {a}")},
+  { i: length      , t: mkType("∀a: {a} -> Int")},
+  { i: first       , t: mkType("∀a: {a} -> <a>")},
+  { i: last        , t: mkType("∀a: {a} -> <a>")},
+  { i: read        , t: mkType("∀a: <a> -> (Unit + (a * <a>))")},
+];
diff --git a/lib/structures/struct.js b/lib/structures/struct.js
new file mode 100644
index 0000000..51c9d33
--- /dev/null
+++ b/lib/structures/struct.js
@@ -0,0 +1,33 @@
+import { unit } from "../primitives/unit.js";
+import { capitalizeFirstLetter } from "../util/util.js";
+import { newProduct, getLeft, getRight } from "./product.js";
+
+export const makeConstructor = nParams => {
+  const internal = (nParams, ret) => {
+    if (nParams === 0) {
+      const result = ret(unit);
+      return result;
+    }
+    return nextParam => {
+      const wrappedName = 'wrapped_' + ret.name;
+      const newRet = {
+        [wrappedName]: inner => newProduct(nextParam)(ret(inner)),
+      }[wrappedName];
+      return internal(nParams-1, newRet);
+    }
+  };
+  const id = x => x;
+  return internal(nParams, id);
+};
+
+export const makeGetters = fieldNames => {
+  if (fieldNames.length === 0) {
+    return [];
+  }
+  const [fieldName, ...rest] = fieldNames;
+  const getterName = `get${capitalizeFirstLetter(fieldName)}`;
+  return [
+    { [getterName]: obj => getLeft(obj) }[getterName],
+    ...makeGetters(rest).map(getter => ({[getter.name]: obj => getter(getRight(obj))}[getter.name])),
+  ];
+};
diff --git a/lib/structures/struct.types.js b/lib/structures/struct.types.js
new file mode 100644
index 0000000..2946f65
--- /dev/null
+++ b/lib/structures/struct.types.js
@@ -0,0 +1,61 @@
+import { getDefaultTypeParser } from "../parser/type_parser.js";
+import { newDynamic } from "../primitives/dynamic.js";
+import { Type, Unit } from "../primitives/primitive_types.js";
+import { zip } from "../util/util.js";
+import { map } from "./list.js";
+import { getLeft, getRight } from "./product.js";
+import { makeConstructor, makeGetters } from "./struct.js";
+import { fnType, prodType } from "./type_constructors.js";
+
+
+// 'fields' is an array of (name: string, type: Type) pairs.
+// e.g.:
+//   [{l: "x", r: Double}, {l: "y", r: Double}]
+//   results in the type (Double × (Double × Unit))
+
+export const structType = fieldTypes => {
+  if (fieldTypes.length === 0) {
+    return Unit;
+  }
+  const [fieldType, ...rest] = fieldTypes;
+  return prodType(_ => fieldType)(_ => structType(rest));
+};
+
+export const makeConstructorType = fieldTypes => {
+  if (fieldTypes.length === 0) {
+    return structType(fieldTypes);
+  }
+  const [fieldType, ...rest] = fieldTypes;
+  return fnType(_ => fieldType)(_ => makeConstructorType(rest));
+};
+
+export const makeGettersTypes = fieldTypes => {
+  const type = structType(fieldTypes);
+  return fieldTypes.map(fieldType => {
+    return fnType(_ => type)(_ => fieldType);
+  });
+};
+
+export const makeModuleStruct = fields => {
+  const fieldNames = map(fields)(getLeft);
+  const fieldTypes = map(fields)(getRight);
+  const type = structType(fieldTypes);
+  const ctor = makeConstructor(fields.length);
+  const ctorType = makeConstructorType(fieldTypes);
+  const getterTypes = makeGettersTypes(fieldTypes);
+  const getters = makeGetters(fieldNames);
+  const module = [
+    {i: type, t: Type},
+    {i: ctor, t: ctorType},
+    ...zip(getters, getterTypes)
+       .map(([getter, getterType]) => newDynamic(getter)(getterType)),
+  ];
+  return module;
+};
+
+const mkType = getDefaultTypeParser();
+
+export const ModuleStruct = [
+  {i: structType, t: mkType("[String*Type] -> Type")},
+  {i: makeModuleStruct, t: mkType("[String*Type] -> [Dynamic]")},
+];
diff --git a/lib/structures/sum.js b/lib/structures/sum.js
new file mode 100644
index 0000000..7d5b76d
--- /dev/null
+++ b/lib/structures/sum.js
@@ -0,0 +1,11 @@
+// Sum-type (also called: tagged union, disjoint union, variant type)
+// A Sum-type always has only two variants, called "left" and "right".
+// Sum-types of more variants (called Enums) can be constructed by nesting Sum-types.
+
+export const newLeft  = left  => ({t: "L", v: left });
+export const newRight = right => ({t: "R", v: right});
+
+export const match = sum => leftHandler => rightHandler =>
+  sum.t === "L"
+    ? leftHandler(sum.v)
+    : rightHandler(sum.v);
diff --git a/lib/structures/sum.types.js b/lib/structures/sum.types.js
new file mode 100644
index 0000000..b9a8b20
--- /dev/null
+++ b/lib/structures/sum.types.js
@@ -0,0 +1,10 @@
+import { getDefaultTypeParser }from "../parser/type_parser.js";
+import { match, newLeft, newRight } from "./sum.js";
+
+const mkType = getDefaultTypeParser();
+
+export const ModuleSum = [
+  { i: newLeft     , t: mkType("∀a,b: a -> (a + b)") },
+  { i: newRight    , t: mkType("∀a,b: b -> (a + b)") },
+  { i: match       , t: mkType("∀a,b,c: (a + b) -> (a -> c) -> (b -> c) -> c") },
+];
diff --git a/lib/structures/type_constructors.js b/lib/structures/type_constructors.js
new file mode 100644
index 0000000..0ec9b65
--- /dev/null
+++ b/lib/structures/type_constructors.js
@@ -0,0 +1,17 @@
+// to break up dependency cycles, type constructors are defined in their own JS module
+
+import { makeTypeConstructor } from "../meta/type_constructor.js";
+
+export const symbolFunction = "Function__c2433e31fa574a2cb3b6b5d62ac9d4b2";
+export const symbolSum      = "Sum__89b731efa6344ea0b6a8663a45cf3ea8";
+export const symbolProduct  = "Product__89351ecdedfb4b05b2a5a6cc0c383e12";
+export const symbolList     = "List__daa8de8a9047435e96034ec64f2da3a1";
+export const symbolSet      = "Set__8fef2c1873df4327ac31bd61d2ecf7e0";
+export const symbolDict     = "Dict__d7158547322549ac9f7f8176aec123dd";
+
+export const fnType   = makeTypeConstructor(symbolFunction)(2);
+export const sumType  = makeTypeConstructor(symbolSum)(2);
+export const prodType = makeTypeConstructor(symbolProduct)(2);
+export const lsType   = makeTypeConstructor(symbolList)(1);
+export const setType  = makeTypeConstructor(symbolSet)(1);
+export const dictType = makeTypeConstructor(symbolDict)(2);
diff --git a/lib/structures/type_constructors.types.js b/lib/structures/type_constructors.types.js
new file mode 100644
index 0000000..04c6eb6
--- /dev/null
+++ b/lib/structures/type_constructors.types.js
@@ -0,0 +1,23 @@
+import { getDefaultTypeParser } from "../parser/type_parser.js";
+import { SymbolT } from "../primitives/primitive_types.js";
+import { dictType, fnType, lsType, prodType, setType, sumType, symbolDict, symbolFunction, symbolList, symbolProduct, symbolSet, symbolSum } from "./type_constructors.js";
+
+const mkType = getDefaultTypeParser();
+
+export const ModuleStructuralSymbols = [
+    { i: symbolSet      , t: SymbolT },
+    { i: symbolList     , t: SymbolT },
+    { i: symbolProduct  , t: SymbolT },
+    { i: symbolSum      , t: SymbolT },
+    { i: symbolDict     , t: SymbolT },
+    { i: symbolFunction , t: SymbolT },
+];
+
+export const ModuleTypeConstructors = [
+    { i: setType     , t: mkType("Type -> Type") },
+    { i: lsType      , t: mkType("Type -> Type") },
+    { i: prodType    , t: mkType("Type -> Type -> Type") },
+    { i: sumType     , t: mkType("Type -> Type -> Type") },
+    { i: dictType    , t: mkType("Type -> Type -> Type") },
+    { i: fnType      , t: mkType("Type -> Type -> Type") },
+];
\ No newline at end of file
diff --git a/lib/symbol.js b/lib/symbol.js
deleted file mode 100644
index 939dc93..0000000
--- a/lib/symbol.js
+++ /dev/null
@@ -1,21 +0,0 @@
-import { eqSymbol, getName } from "../primitives/symbol.js";
-import { Bool, SymbolT, Type } from "../primitives/types.js";
-import { String } from "../structures/list.js";
-import { typedFnType } from "../structures/types.js";
-
-// The way instances of SymbolT are currently encoded, their constructor is not a valid DOPE function, because it is impure.
-// The only way to construct symbols is to do it in JS code.
-
-// At some point, we should start encoding SymbolTs as UUIDs rather than JS-Symbols.
-
-export const ModuleSymbol = {l:[
-  {i: SymbolT, t: Type},
-
-  ...typedFnType(getName, fnType =>
-    fnType
-      (SymbolT)
-      (String)
-  ),
-
-  ...typedFnType(eqSymbol, fnType => fnType(() => SymbolT)(fnType(SymbolT)(() => Bool))),
-]};
diff --git a/lib/type_constructor.js b/lib/type_constructor.js
deleted file mode 100644
index 99ee760..0000000
--- a/lib/type_constructor.js
+++ /dev/null
@@ -1,14 +0,0 @@
-import { Int, SymbolT, Type } from "../primitives/types.js";
-import { typedFnType } from "../structures/types.js";
-import { makeTypeConstructor } from "../type_constructor.js";
-
-// This function and its type signature cannot be in the same file as 'makeTypeConstructor' because then we get an import cycle among JS modules.
-export const ModuleTypeConstructor = {l:[
-  ...typedFnType(makeTypeConstructor, fnType =>
-    fnType
-      (SymbolT)
-      (fnType
-        (Int)
-        (Type)
-      )),
-]};
diff --git a/lib/util/defaultmap.js b/lib/util/defaultmap.js
new file mode 100644
index 0000000..e863962
--- /dev/null
+++ b/lib/util/defaultmap.js
@@ -0,0 +1,18 @@
+
+// export class DefaultMap {
+//   constructor(defaultValue, ...rest) {
+//     this.defaultValue = defaultValue;
+//     this.m = new Map(rest);
+//   }
+//   getdefault(key, addToMapping = false) {
+//     return this.m.get(key) || (() => {
+//       const val = this.defaultValue(key);
+//       if (addToMapping)
+//         this.m.set(key, val);
+//       return val;
+//     })();
+//   }
+//   entries() {
+//     return this.m.entries();
+//   }
+// }
diff --git a/util/pretty.js b/lib/util/pretty.js
similarity index 72%
rename from util/pretty.js
rename to lib/util/pretty.js
index 05865d9..b8e09cf 100644
--- a/util/pretty.js
+++ b/lib/util/pretty.js
@@ -1,17 +1,23 @@
 import { inspect } from 'node:util';
-import { symbolDict, symbolFunction, symbolList, symbolProduct, symbolSet, symbolSum } from '../structures/types.js';
+import { symbolDict, symbolFunction, symbolList, symbolProduct, symbolSum } from '../structures/type_constructors.js';
+import { symbolSet } from "../structures/type_constructors.js";
 import { mapRecursiveStructure } from './util.js';
+import { getHumanReadableName } from '../primitives/symbol.js';
 
 export function pretty(obj) {
   return inspect(obj, { colors: true, depth: null, breakLength: 120 });
 }
 
-// Pretty print type
+// Pretty print Type
 export const prettyT = type => {
   return mapRecursiveStructure(([type, m, seen], map) => {
     if (typeof type === "symbol") {
+      // type variable
       return type.description;
     }
+    // if (type.params === undefined) {
+    //   throw new Error("parameter is not a Type ... did you mean to call prettyGenT instead?")
+    // }
     if (!m.has(type)) {
       m.add(type); // next time we encounter this type, we'll only render a placeholder
       const params = type.params.map(p => map([p(type), m, seen])());
@@ -19,12 +25,10 @@ export const prettyT = type => {
       const annot = seen.has(type) ? seen.get(type) : ``;
       return renderType(type.symbol, annot, params);
     }
-    else {
-      if (!seen.has(type)) {
-        seen.set(type, `#${seen.size}`);
-      }
-      return seen.get(type);
+    if (!seen.has(type)) {
+      seen.set(type, `#${seen.size}`);
     }
+    return seen.get(type);
   })([type, new Set(), new Map()])();
 };
 
@@ -36,9 +40,10 @@ const renderType = (symbol, annot, params) => {
     [symbolSum]     : `${annot}(${params[0]} + ${params[1]})`,
     [symbolProduct] : `${annot}(${params[0]} ⨯ ${params[1]})`,
     [symbolDict]    : `${annot}(${params[0]} => ${params[1]})`,
-  }[symbol] || symbol.description;
+  }[symbol] || getHumanReadableName(symbol);
 };
 
+// Pretty print GenericType
 export const prettyGenT = genericType => {
   return `∀${[...genericType.typeVars].map(prettyT).sort((a, b) => a.localeCompare(b)).join(",")}: ${prettyT(genericType.type)}`;
 };
diff --git a/lib/util/random.js b/lib/util/random.js
new file mode 100644
index 0000000..81d659e
--- /dev/null
+++ b/lib/util/random.js
@@ -0,0 +1,16 @@
+// IMPURE
+export const genUUID = (len=16) => {
+  const arr = crypto.getRandomValues(new Uint8Array(len));
+  let result = "";
+  for (let i=0; i<len; i++) {
+    const unsignedByte = arr[i];
+    if (unsignedByte < 16) {
+      result += '0' + unsignedByte.toString(16);
+    } else {
+      result += unsignedByte.toString(16);
+    }
+  }
+  return result;
+};
+
+console.log(genUUID())
\ No newline at end of file
diff --git a/lib/util/rbtree_wrapper.js b/lib/util/rbtree_wrapper.js
new file mode 100644
index 0000000..51f34e5
--- /dev/null
+++ b/lib/util/rbtree_wrapper.js
@@ -0,0 +1,21 @@
+// Tiny wrapper around function-red-black-tree that overrides the [inspect.custom] symbol so when we print it (during debugging) we just see the (key=>value)-pairs instead of the tree structure.
+
+import createRBTree from "functional-red-black-tree";
+import { inspect } from "util";
+
+export class RBTreeWrapper {
+  constructor(tree) {
+    this.tree = tree;
+  }
+
+  static new(compareFn) {
+    return new RBTreeWrapper(createRBTree(compareFn))
+  }
+  
+  // pretty print to console
+  [inspect.custom](depth, options, inspect) {
+    const entries = [];
+    this.tree.forEach((key, val) => { entries.push(`${inspect(key)} => ${inspect(val)}`); });
+    return `RBTree(${this.tree.length}) {${entries.join(', ')}}`;
+  }
+}
diff --git a/lib/util/util.js b/lib/util/util.js
new file mode 100644
index 0000000..4e401ca
--- /dev/null
+++ b/lib/util/util.js
@@ -0,0 +1,27 @@
+// zip two arrays
+export function zip(a, b) {
+  return a.map((k, i) => [k, b[i]]);
+}
+
+export function capitalizeFirstLetter(val) {
+  return String(val).charAt(0).toUpperCase() + String(val).slice(1);
+}
+
+const _mapRecursiveStructure = mapping => transform => root => {
+  const found = mapping.get(root);
+  if (found) {
+    // already mapped
+    // return existing result to prevent endless recursion
+    return found;
+  }
+  // note the indirection (wrapped in lamda), this allows the user to recursively map the children (which may refer to the root) without yet having finished mapping the root.
+  let memo;
+  const result = () => {
+    // memoization is necessary for correctness
+    return memo || (memo = transform(root, _mapRecursiveStructure(mapping)(transform)));
+  };
+  mapping.set(root, result);
+  return result;
+};
+
+export const mapRecursiveStructure = _mapRecursiveStructure(new Map());
diff --git a/versioning/slot.js b/lib/versioning/slot.js
similarity index 96%
rename from versioning/slot.js
rename to lib/versioning/slot.js
index 163c90c..49cd217 100644
--- a/versioning/slot.js
+++ b/lib/versioning/slot.js
@@ -1,4 +1,4 @@
-import { add, emptySet, forEach } from "../structures/set.js";
+import { add, emptySet, forEach } from "../../structures/set.js";
 import { deepEqual } from "../util/util.js";
 import {inspect} from "node:util";
 import { compareSlots } from "../compare/versioning.js";
diff --git a/versioning/types.js b/lib/versioning/types.js
similarity index 100%
rename from versioning/types.js
rename to lib/versioning/types.js
diff --git a/versioning/value.js b/lib/versioning/value.js
similarity index 100%
rename from versioning/value.js
rename to lib/versioning/value.js
diff --git a/parser/parser.js b/parser/parser.js
deleted file mode 100644
index ed7c91f..0000000
--- a/parser/parser.js
+++ /dev/null
@@ -1,174 +0,0 @@
-import { Bool, Char, Double, Int, Unit } from "../primitives/types.js";
-import { dictType, fnType, lsType, prodType, setType, sumType } from "../structures/types.js";
-
-const bracketOperators = new Map([
-  ['(', [')', null]],
-  ['[', [']', lsType]],
-  ['{', ['}', setType]],
-
-  // can only occur at beginning
-  // we use these to extract the type variables
-  ['∀', [':', null]],
-]);
-
-const infixOperators = new Map([
-  ['+', sumType],
-  ['|', sumType],
-  ['⨯', prodType],
-  ['*', prodType],
-  ['→', fnType],
-  ['->', fnType],
-  ['⇒', dictType],
-  ['=>', dictType],
-
-  // only used for type variables (e.g., ∀a,b,c:)
-  [',', fnX => fnY => {
-    const x = fnX();
-    const y = fnY();
-    return Array.isArray(x) ? x.concat(y) : [x].concat(y)
-  }],
-]);
-
-const a = Symbol('a');
-const b = Symbol('b');
-const c = Symbol('c');
-const d = Symbol('d');
-const e = Symbol('e');
-
-const primitives = new Map([
-  ['Int', Int],
-  ['Double', Double],
-  ['Bool', Bool],
-  ['Char', Char],
-  ['Unit', Unit],
-  ['a', a],
-  ['b', b],
-  ['c', c],
-  ['d', d],
-  ['e', e],
-]);
-
-const TOKENS = [
-  ...bracketOperators.keys(),
-  ...[...bracketOperators.values()].map(v => v[0]),
-  ...infixOperators.keys(),
-  ...primitives.keys(),
-];
-
-// console.log('TOKENS =', TOKENS);
-
-const tokenize = expr => {
-  const tokens = [];
-  let i=0;
-  outerloop: while (i<expr.length) {
-    if (/\s/.test(expr[i])) {
-      i++;
-      continue outerloop; // skip whitespace
-    }
-    if (expr[i] === '#') {
-      const label = '#' + parseInt(expr.slice(i+1));
-      tokens.push(label);
-      i += label.length;
-      continue outerloop;
-    }
-    for (const token of TOKENS) {
-      if (expr.startsWith(token, i)) {
-        tokens.push(token);
-        i += token.length;
-        continue outerloop;
-      }
-    }
-    throw new Error(`Couldn't match any token at position ${i} in\n  ${expr}\n  ${' '.repeat(i)}^`);
-  }
-  // console.log({tokens});
-  return tokens;
-}
-
-const consumeGroup = (tokens) => {
-  const bracket = bracketOperators.get(tokens[0]);
-  if (bracket === undefined) {
-    // no group, just a single token:
-    const [firstToken, ...rest] = tokens;
-    return [[firstToken], null, rest];
-  }
-  else {
-    // find where group ends:
-    const [closing, fn] = bracket;
-    const opening = tokens[0]
-    let depth = 1;
-    let i = 1;
-    for (; i<tokens.length; i++) {
-      if (tokens[i] === opening) {
-        depth++;
-      }
-      else if (tokens[i] === closing) {
-        depth--;
-      }
-      if (depth === 0) {
-        break;
-      }
-    }
-    const tokensInGroup = tokens.slice(1, i); // don't include brackets
-    const rest = tokens.slice(i+1);
-    return [tokensInGroup, fn, rest];
-  }
-}
-
-const parseGroup = (tokensInGroup, fn, labels, label) => {
-  // console.log('parseGroup ', tokensInGroup, fn);
-  return (fn === null)
-    ? __parse(tokensInGroup, labels, label)
-    : fn(self => {
-        return __parse(tokensInGroup, extendLabels(labels, label, self));
-      });
-}
-
-const extendLabels = (labels, label, self) => {
-  return (label === null) ? labels : new Map([...labels, [label, self]])
-};
-
-const __parse = (tokens, labels = new Map(), label = null) => {
-  // console.log('parse ', tokens);
-  if (tokens[0].startsWith('#')) {
-    if (labels.has(tokens[0])) {
-      return labels.get(tokens[0]);
-    }
-    else {
-      // pass label and parse 'rest'
-      return __parse(tokens.slice(1), labels, tokens[0]);
-    }
-  }
-  if (tokens.length === 1) {
-    return primitives.get(tokens[0]);
-  }
-  else {
-    const [lhsTokens, fnGrp, rest] = consumeGroup(tokens);
-    if (rest.length === 0) {
-      return parseGroup(lhsTokens, fnGrp, labels, label);
-    }
-    const [operator, ...rhsTokens] = rest;
-    for (const [operatorChar, fn] of infixOperators) {
-      if (operator === operatorChar) {
-        return fn
-          (self => {
-            return parseGroup(lhsTokens, fnGrp, extendLabels(labels, label, self));
-          })(self => {
-            return __parse(rhsTokens, extendLabels(labels, label, self));
-          });
-      }
-    }
-    throw new Error("unknown operator: "+operator)
-  }
-};
-
-export const parse = expr => {
-  const tokens = tokenize(expr);
-  if (tokens[0] === '∀') {
-    // generic type
-    const [typeVarTokens, _, rest] = consumeGroup(tokens);
-    const typeVars = [].concat(__parse(typeVarTokens))
-    const type = __parse(rest);
-    return { typeVars, type };
-  }
-  return __parse(tokens);
-}
diff --git a/primitives/bool.js b/primitives/bool.js
deleted file mode 100644
index 1a1495c..0000000
--- a/primitives/bool.js
+++ /dev/null
@@ -1,15 +0,0 @@
-import { fnType, typedFnType } from "../structures/types.js";
-import { Type } from "./types.js";
-import { Bool } from "./types.js";
-
-const eqBool = x => y => x === y;
-
-export const ModuleBool = {l:[
-  {i: true , t: Bool},
-  {i: false, t: Bool},
-
-  {i: Bool , t: Type},
-
-  // Bool -> Bool -> Bool
-  ...typedFnType(eqBool, fnType => fnType(() => Bool)(fnType(Bool)(() => Bool))),
-]};
diff --git a/primitives/byte.js b/primitives/byte.js
deleted file mode 100644
index 0ff79bc..0000000
--- a/primitives/byte.js
+++ /dev/null
@@ -1,11 +0,0 @@
-import { typedFnType } from "../structures/types.js";
-import { Type } from "./types.js";
-import {Byte, Bool} from "./types.js";
-
-const eqByte = x => y => x === y;
-
-export const ModuleByte = {l:[
-  {i: Byte                 , t: Type                 },
-
-  ...typedFnType(eqByte, fnType => fnType(() => Byte)(fnType(Byte)(() => Bool))),
-]};
diff --git a/primitives/char.js b/primitives/char.js
deleted file mode 100644
index 11d355f..0000000
--- a/primitives/char.js
+++ /dev/null
@@ -1,16 +0,0 @@
-import { typedFnType } from "../structures/types.js";
-import { Type } from "./types.js";
-import {Char, Bool} from "./types.js";
-
-const eq = x => y => x === y;
-
-export const ModuleChar = {l:[
-  {i: Char, t: Type},
-
-  ...typedFnType(eq, fnType =>
-    fnType
-      (Char)
-      (fnType
-        (Char)
-        (Bool))),
-]};
diff --git a/primitives/double.js b/primitives/double.js
deleted file mode 100644
index 7de914c..0000000
--- a/primitives/double.js
+++ /dev/null
@@ -1,15 +0,0 @@
-import { typedFnType } from "../structures/types.js";
-import { Type } from "./types.js";
-import {Bool, Double} from "./types.js";
-
-export const addDouble = x => y => x + y;
-export const mulDouble = x => y => x * y;
-export const eqDouble  = x => y => x === y;
-
-export const ModuleDouble = {l:[
-  {i: Double, t: Type},
-
-  ...typedFnType(addDouble, fnType => fnType(() => Double)(fnType(Double)(() => Double))),
-  ...typedFnType(mulDouble, fnType => fnType(() => Double)(fnType(Double)(() => Double))),
-  ...typedFnType(eqDouble, fnType => fnType(() => Double)(fnType(Double)(() => Bool))),
-]};
diff --git a/primitives/dynamic.js b/primitives/dynamic.js
deleted file mode 100644
index bd6584f..0000000
--- a/primitives/dynamic.js
+++ /dev/null
@@ -1,19 +0,0 @@
-import { typedFnType } from "../structures/types.js";
-import { Top, Type } from "./types.js";
-import { makeTypeConstructor } from "../type_constructor.js";
-
-// A type-link, connecting a value to its Type.
-export const symbolDynamic = Symbol('Dynamic');
-export const Dynamic = makeTypeConstructor(symbolDynamic)(0);
-
-export const getInst = lnk => lnk.i;
-export const getType = lnk => lnk.t;
-
-export const ModuleDynamic = {l:[
-  {i: Dynamic, t: Type},
-  {i: Top    , t: Type},
-
-  ...typedFnType(getInst, fnType => fnType(() => Dynamic)(() => Top)),
-  ...typedFnType(getType, fnType => fnType(() => Dynamic)(() => Top)),
-]};
-
diff --git a/primitives/generic_type.js b/primitives/generic_type.js
deleted file mode 100644
index 580c34b..0000000
--- a/primitives/generic_type.js
+++ /dev/null
@@ -1,21 +0,0 @@
-import { newLeft, newRight } from "../structures/sum.js";
-import { setType, sumType, typedFnType } from "../structures/types.js";
-import { Top, GenericType, SymbolT, Type, Unit } from "./types.js";
-import { unit } from "./unit.js";
-
-export const getType     = genericType => genericType.type;
-export const getTypeVars = genericType => genericType.typeVars;
-
-export const toNonGeneric = genericType => (genericType.typeVars.size === 0)
-  ? newRight(genericType.type)
-  : newLeft(unit);
-
-export const ModuleGenericType = {l:[
-  {i: GenericType, t: Top},
-
-  // ...typedFnType(getType, fnType => fnType(() => GenericType)(() => Type)),
-
-  // ...typedFnType(getTypeVars, fnType => fnType(() => GenericType)(() => set(() => SymbolT))),
-
-  ...typedFnType(toNonGeneric, fnType => fnType(() => GenericType)(sumType(() => Unit)(() => () => Type))),
-]};
diff --git a/primitives/int.js b/primitives/int.js
deleted file mode 100644
index d4eb833..0000000
--- a/primitives/int.js
+++ /dev/null
@@ -1,19 +0,0 @@
-import { typedFnType } from "../structures/types.js";
-import { Type } from "./types.js";
-
-import {Bool, Int} from "./types.js";
-
-export const addInt = x => y => x + y;
-export const mulInt = x => y => x * y;
-export const eqInt  = x => y => x === y;
-
-const serialize   = x => x.toString();
-const deserialize = str => BigInt(str);
-
-export const ModuleInt = {l:[
-  {i: Int                , t: Type               },
-
-  ...typedFnType(addInt, fnType => fnType(() => Int)(fnType(Int)(() => Int))),
-  ...typedFnType(mulInt, fnType => fnType(() => Int)(fnType(Int)(() => Int))),
-  ...typedFnType(eqInt , fnType => fnType(() => Int)(fnType(Int)(() => Bool))),
-]};
diff --git a/primitives/symbol.js b/primitives/symbol.js
deleted file mode 100644
index b0e56ad..0000000
--- a/primitives/symbol.js
+++ /dev/null
@@ -1,8 +0,0 @@
-// The functions are only defined here. For their types, see lib/symbol.js
-
-// Cannot turn the constructor into a DOPE function, because it is NOT PURE:
-// export const constructSymbol = name => Symbol(name);
-
-export const getName = symbol => symbol.description;
-
-export const eqSymbol = a => b => a === b;
diff --git a/primitives/type.js b/primitives/type.js
deleted file mode 100644
index a8dbd11..0000000
--- a/primitives/type.js
+++ /dev/null
@@ -1,33 +0,0 @@
-import { Bool, SymbolT, Type } from "./types.js";
-import { isFunction, lsType, typedFnType } from "../structures/types.js";
-import { getSymbol, getParams } from "../type_constructor.js";
-import { deepEqual } from "../util/util.js";
-
-// we can test whether types are equal:
-export const eqType = t1 => t2 => deepEqual(t1, t2);
-
-// a module is just a set of typed objects
-// each 'typed object' is implicitly an instance of TypeLink (defined below)
-export const ModuleType = {l:[  
-  // TODO? maybe follow Lean so
-  //    Type.{0} : Type.{1}
-  //    Type.{1} : Type.{2}
-  //    ...
-  // see: https://lean-lang.org/functional_programming_in_lean/functor-applicative-monad/universes.html
-
-  {i: Type, t: Type},
-
-  // Type -> Type -> Bool
-  ...typedFnType(eqType, fnType =>
-    fnType
-      (Type)
-      (fnType
-        (Type)
-        (Bool)
-      )),
-  
-  ...typedFnType(getSymbol, fnType => fnType(() => Type)(() => SymbolT)),
-  ...typedFnType(getParams, fnType => fnType(() => Type)(() => lsType(() =>Type))),
-
-  ...typedFnType(isFunction, fnType => fnType(() => Type)(() => Bool)),
-]};
\ No newline at end of file
diff --git a/primitives/types.js b/primitives/types.js
deleted file mode 100644
index f8e05f4..0000000
--- a/primitives/types.js
+++ /dev/null
@@ -1,51 +0,0 @@
-// to break up dependency cycles, primitive types are defined in their own JS module
-
-import { makeTypeConstructor } from "../type_constructor.js";
-
-export const SymbolInt         = Symbol('Int');
-export const SymbolBool        = Symbol('Bool');
-export const SymbolDouble      = Symbol('Double');
-export const SymbolByte        = Symbol('Byte');
-export const SymbolChar        = Symbol('Char');
-export const SymbolUnit        = Symbol('Unit');
-export const SymbolBottom      = Symbol('⊥');
-export const SymbolSymbol      = Symbol('Symbol');
-export const SymbolType        = Symbol('Type');
-export const symbolTop         = Symbol('⊤');
-export const SymbolGenericType = Symbol('GenericType');
-
-export const Int     = makeTypeConstructor(SymbolInt)(0);
-export const Bool    = makeTypeConstructor(SymbolBool)(0);
-export const Double  = makeTypeConstructor(SymbolDouble)(0);
-export const Byte    = makeTypeConstructor(SymbolByte)(0);
-export const Char    = makeTypeConstructor(SymbolChar)(0);
-
-// Unit type has only 1 instance, the empty tuple.
-export const Unit    = makeTypeConstructor(SymbolUnit)(0);
-
-// Bottom type has no instances.
-export const Bottom  = makeTypeConstructor(SymbolBottom)(0);
-
-export const SymbolT = makeTypeConstructor(SymbolSymbol)(0);
-
-// Types are typed by Top
-export const Type    = makeTypeConstructor(SymbolType)(0);
-
-export const GenericType = makeTypeConstructor(SymbolGenericType)(0);
-
-// Everything is typed by Top
-export const Top = makeTypeConstructor(symbolTop)(0);
-
-export const ModuleSymbols = {l:[
-  {i: SymbolInt        , t: SymbolT},
-  {i: SymbolBool       , t: SymbolT},
-  {i: SymbolDouble     , t: SymbolT},
-  {i: SymbolByte       , t: SymbolT},
-  {i: SymbolChar       , t: SymbolT},
-  {i: SymbolUnit       , t: SymbolT},
-  {i: SymbolBottom     , t: SymbolT},
-  {i: SymbolSymbol     , t: SymbolT},
-  {i: SymbolType       , t: SymbolT},
-  {i: SymbolGenericType, t: SymbolT},
-  {i: symbolTop        , t: SymbolT},
-]};
diff --git a/primitives/unit.js b/primitives/unit.js
deleted file mode 100644
index 99f1b30..0000000
--- a/primitives/unit.js
+++ /dev/null
@@ -1,15 +0,0 @@
-import { typedFnType } from "../structures/types.js";
-import { Bool, Type, Unit } from "./types.js";
-
-export const eqUnit = x => y => x === y;
-
-export const unit = {};
-
-export const ModuleUnit = {l:[
-  {i: unit, t: Unit},
-
-  {i: Unit, t: Type},
-
-  // Unit -> Unit -> Bool
-  ...typedFnType(eqUnit, fnType => fnType(() => Unit)(fnType(Unit)(() => Bool))),
-]};
diff --git a/stdlib.js b/stdlib.js
deleted file mode 100644
index 0c5e726..0000000
--- a/stdlib.js
+++ /dev/null
@@ -1,42 +0,0 @@
-import { ModuleSymbol } from "./lib/symbol.js";
-import { ModuleTypeConstructor } from "./lib/type_constructor.js";
-import { ModuleBool } from "./primitives/bool.js";
-import { ModuleByte } from "./primitives/byte.js";
-import { ModuleChar } from "./primitives/char.js";
-import { ModuleDouble } from "./primitives/double.js";
-import { ModuleInt } from "./primitives/int.js";
-import { ModuleSymbols } from "./primitives/types.js";
-import { ModuleUnit } from "./primitives/unit.js";
-import { ModuleFunction } from "./structures/function.js";
-import { ModuleList } from "./structures/list.js";
-import { ModuleProduct } from "./structures/product.js";
-import { ModuleSum } from "./structures/sum.js";
-import { ModuleType } from "./primitives/type.js";
-import { ModuleDynamic } from "./primitives/dynamic.js";
-import { ModuleSet } from "./structures/set.js";
-import { ModuleGenericType } from "./primitives/generic_type.js";
-
-export const ModuleStd = {l:[
-  ...ModuleType.l,
-  ...ModuleGenericType.l,
-  ...ModuleDynamic.l,
-
-  ...ModuleTypeConstructor.l,
-  ...ModuleSymbols.l,
-
-  // Primitive types
-  ...ModuleBool.l,
-  ...ModuleByte.l,
-  ...ModuleChar.l,
-  ...ModuleDouble.l,
-  ...ModuleInt.l,
-  ...ModuleSymbol.l,
-  ...ModuleUnit.l,
-
-  // Types that consist of other types
-  ...ModuleFunction.l,
-  ...ModuleList.l,
-  ...ModuleProduct.l,
-  ...ModuleSum.l,
-  ...ModuleSet.l,
-]};
diff --git a/structures/function.js b/structures/function.js
deleted file mode 100644
index 38424df..0000000
--- a/structures/function.js
+++ /dev/null
@@ -1,14 +0,0 @@
-import { Type } from "../primitives/types.js";
-import { typedFnType } from "./types.js";
-import { fnType } from "./types.js";
-
-export const ModuleFunction = {l:[
-  // binary type constructor: Type -> Type -> Type
-  ...typedFnType(fnType, fnType => fnType
-    /* in  */ (Type)
-    /* out */ (fnType
-      /* in  */ (Type)
-      /* out */ (Type)
-    )
-  ),
-]};
diff --git a/structures/list.js b/structures/list.js
deleted file mode 100644
index 406edba..0000000
--- a/structures/list.js
+++ /dev/null
@@ -1,82 +0,0 @@
-import { typedFnType } from "./types.js";
-import { Char, GenericType, Type } from "../primitives/types.js";
-import { Int } from "../primitives/types.js";
-import { makeGeneric } from "../generics/generics.js";
-import { lsType } from "./types.js";
-import { Dynamic } from "../primitives/dynamic.js"
-
-// 'normal' implementation
-export const emptyList = {l:[]};
-// const emptyListType = makeGeneric(a => lsType(() => a));
-export const get = ls => i => ls.l[i];
-export const put = ls => i => elem => ({l: ls.l.with(Number(i), elem)});
-export const push = ls => elem => ({l:ls.l.concat([elem])});
-export const map = ls => fn => ({ l: ls.l.map(elem => fn(elem)) });
-export const length = ls => ls.l.length;
-export const fold = ls => callback => initial => {
-  let acc = initial;
-  for (let i=0; i<ls.l.length; i++) {
-    acc = callback(acc)(ls.l[i]);
-  }
-  return acc;
-}
-
-export const String = lsType(() =>Char); // alias
-export const Module = lsType(() =>Dynamic);
-
-export const ModuleList = {l:[
-  // // Type -> Type
-  // ...typedFnType(lsType, fnType =>
-  //   fnType
-  //     /* in  */ (Type)
-  //     /* out */ (Type)
-  // ),
-
-  // // [a]
-  // // {i: emptyList, t: emptyListType},
-  // // {i: emptyListType, t: GenericType},
-
-  // // [a] -> Int -> a
-  // ...typedFnType(get, fnType =>
-  //   makeGeneric(a =>
-  //     fnType
-  //       /* in  */ (() => lsType(() => a))
-  //       /* out */ (() => fnType
-  //         /* in  */ (() => Int)
-  //         /* out */ (() => a)
-  //       )), GenericType),
-
-  // // [a] -> Int -> a -> [a]
-  // ...typedFnType(put, fnType =>
-  //   makeGeneric(a =>
-  //     fnType
-  //       /* in  */ (() => lsType(() => a))
-  //       /* out */ (() => fnType
-  //         /* in  */ (() => Int)
-  //         /* out */ (() => fnType
-  //           /* in  */ (() => a)
-  //           /* out */ (() => lsType(() => a))
-  //         )
-  //       )), GenericType),
-
-  // // [a] -> a -> [a]
-  // ...typedFnType(push, fnType =>
-  //   makeGeneric(a =>
-  //     fnType
-  //       (() => lsType(() => a))
-  //       (() => fnType
-  //         (() => a)
-  //         (() => lsType(() => a))
-  //       )
-  //   ), GenericType),
-
-  // // [a] -> (a -> b) -> [b]
-  // ...typedFnType(map, fnType =>
-  //   makeGeneric((a, b) =>
-  //     fnType
-  //       (() => lsType(() => a))
-  //       (() => fnType
-  //         (() => fnType(() => a)(() => b))
-  //         (() => lsType(() => b))
-  //       )), GenericType),
-]};
diff --git a/structures/product.types.js b/structures/product.types.js
deleted file mode 100644
index 5ba90bd..0000000
--- a/structures/product.types.js
+++ /dev/null
@@ -1,27 +0,0 @@
-import { makeGeneric } from "../generics/generics.js";
-import { Type, GenericType } from "../primitives/types.js";
-import { newProduct, getLeft, getRight } from "./product.js";
-import { typedFnType, prodType } from "./types.js";
-
-export const ModuleProduct = {
-  l: [
-    // binary type constructor
-    // Type -> Type -> Type
-    ...typedFnType(prodType, fnType => fnType(Type)(fnType(Type)(Type)
-    )
-    ),
-
-    // a -> b -> (a, b)
-    ...typedFnType(newProduct, fnType => makeGeneric((a, b) => fnType(a)(fnType(b)(prodType(() => a)(() => b))
-    )
-    ), GenericType),
-
-    // (a, b) -> a
-    ...typedFnType(getLeft, fnType => makeGeneric((a, b) => fnType(prodType(() => a)(() => b))(a)
-    ), GenericType),
-
-    // (a, b) -> b
-    ...typedFnType(getRight, fnType => makeGeneric((a, b) => fnType(prodType(() => a)(() => b))(b)
-    ), GenericType),
-  ]
-};
diff --git a/structures/set.js b/structures/set.js
deleted file mode 100644
index 00a6717..0000000
--- a/structures/set.js
+++ /dev/null
@@ -1,40 +0,0 @@
-import createRBTree from "functional-red-black-tree";
-import { inspect } from "node:util";
-
-export class RBTreeWrapper {
-  constructor(tree) {
-    this.tree = tree;
-  }
-  // pretty print to console
-  [inspect.custom](depth, options, inspect) {
-    const entries = [];
-    this.tree.forEach((key,val) => {entries.push(`${inspect(key)} => ${inspect(val)}`);});
-    return `RBTree(${this.tree.length}) {${entries.join(', ')}}`;
-  }
-}
-
-// (a -> a -> Int) -> Set(a)
-export const emptySet = compareFn => new RBTreeWrapper(createRBTree((x, y) => compareFn(x)(y)));
-
-
-export const has = set => key => set.tree.get(key) === true;
-export const add = set => key => set.tree.get(key) === true ? set : new RBTreeWrapper(set.tree.insert(key, true));
-export const remove = set => key => new RBTreeWrapper(set.tree.remove(key));
-export const length = set => set.tree.length;
-
-export const first = set => set.tree.begin;
-export const last  = set => set.tree.end;
-
-// test if iterator is 'done', and if not, get element and advance iterator.
-export const read = iter => ifNotDone => ifDone => {
-  if (iter !== undefined && iter.valid) {
-    return ifNotDone(iter.key)(iter.clone().next());
-  }
-  else {
-    return ifDone();
-  }
-};
-
-export const forEach = set => fn => {
-  set.tree.forEach(key => { fn(key); });
-};
diff --git a/structures/set.types.js b/structures/set.types.js
deleted file mode 100644
index 6d900c3..0000000
--- a/structures/set.types.js
+++ /dev/null
@@ -1,31 +0,0 @@
-import { makeGeneric } from "../generics/generics.js";
-import { Int } from "../primitives/types.js";
-import { emptySet, has, add } from "./set.js";
-import { fnType, setType } from "./types.js";
-
-const emptySetType = makeGeneric(a =>
-  fnType
-    // comparison function:
-    (_ => fnType
-      (_ => a)
-      (_ => fnType(_ => a)(_ => Int)))
-    // the set:
-    (_ => setType(_ => a))
-);
-
-export const ModuleSet = {
-  l: [
-    // Type -> Type
-    ...typedFnType(setType, fnType => fnType(_ => Type)(_ => Type)
-    ),
-
-    { i: emptySet, t: emptySetType },
-    { i: emptySetType, t: GenericType },
-
-    ...typedFnType(has, fnType => makeGeneric(a => fnType(_ => setType(_ => a))(_ => fnType(_ => a)(_ => Bool)
-    )), GenericType),
-
-    ...typedFnType(add, fnType => makeGeneric(a => fnType(setType(_ => a))(fnType(a)(setType(_ => a))
-    )), GenericType),
-  ]
-};
diff --git a/structures/struct.js b/structures/struct.js
deleted file mode 100644
index c2edd7f..0000000
--- a/structures/struct.js
+++ /dev/null
@@ -1,65 +0,0 @@
-import { Unit } from "../primitives/types.js";
-import { unit } from "../primitives/unit.js";
-import { capitalizeFirstLetter } from "../util/util.js";
-import { newProduct, getLeft, getRight } from "./product.js";
-import { fnType, prodType } from "./types.js";
-
-// 'fields' is an array of (name: string, type: Type) pairs.
-// e.g.:
-//   [{l: "x", r: Double}, {l: "y", r: Double}]
-//   results in the type (Double × (Double × Unit))
-export const structType = fields => {
-  if (fields.length === 0) {
-    return Unit;
-  }
-  const [field, ...rest] = fields;
-  const fieldType = getRight(field);
-  return prodType(() => fieldType)(() => structType(rest));
-};
-
-export const makeConstructor = fields => {
-  const internal = (nParams, ret) => {
-    if (nParams === 0) {
-      const result = ret(unit);
-      return result;
-    }
-    return nextParam => {
-      const wrappedName = 'wrapped_' + ret.name;
-      const newRet = {
-        [wrappedName]: inner => newProduct(nextParam)(ret(inner)),
-      }[wrappedName];
-      return internal(nParams-1, newRet);
-    }
-  };
-  const id = x => x;
-  return internal(fields.length, id);
-};
-
-export const makeConstructorType = type => fields => {
-  if (fields.length === 0) {
-    return type;
-  }
-  const [field, ...rest] = fields;
-  const fieldType = getRight(field);
-  return fnType(() => fieldType)(() => makeConstructorType(rest));
-};
-
-export const makeGetters = fields => {
-  if (fields.length === 0) {
-    return [];
-  }
-  const [field, ...rest] = fields;
-  const fieldName = getLeft(field);
-  const getterName = `get${capitalizeFirstLetter(fieldName)}`;
-  return [
-    { [getterName]: obj => getLeft(obj) }[getterName],
-    ...makeGetters(rest).map(getter => ({[getter.name]: obj => getter(getRight(obj))}[getter.name])),
-  ];
-};
-
-export const makeGettersTypes = type => fields => {
-  return fields.map(field => {
-    const fieldType = getRight(field);
-    return fnType(() => type)(() => fieldType);
-  });
-};
diff --git a/structures/sum.js b/structures/sum.js
deleted file mode 100644
index f360af1..0000000
--- a/structures/sum.js
+++ /dev/null
@@ -1,62 +0,0 @@
-// Sum-type (also called: tagged union, disjoin union, variant type)
-// A Sum-type always has only two variants, called "left" and "right".
-// Sum-types of more variants (called Enums) can be constructed by nesting Sum-types.
-
-import { prodType } from "./types.js";
-import { GenericType, Type } from "../primitives/types.js";
-import { typedFnType } from "./types.js";
-import { makeGeneric } from "../generics/generics.js";
-import { sumType } from "./types.js";
-
-export const newLeft  = left  => ({t: "L", v: left }); // 't': tag, 'v': value
-export const newRight = right => ({t: "R", v: right});
-
-// signature:
-//   sum-type -> (leftType -> resultType, rightType -> resultType) -> resultType
-export const match = sum => handlers =>
-  sum.t === "L"
-    ? handlers.l(sum.v)
-    : handlers.r(sum.v);
-
-export const ModuleSum = {l:[
-  // binary type constructor
-  // Type -> Type -> Type
-  ...typedFnType(sumType, fnType =>
-    fnType
-      (() => Type)
-      (() => fnType
-        (() => Type)
-        (() => Type)
-      ),
-    ),
-
-  // // a -> a | b
-  // ...typedFnType(newLeft, fnType =>
-  //   makeGeneric((a, b) =>
-  //     fnType
-  //       (a)
-  //       (sumType(() => a)(() => b))
-  //   ), GenericType),
-
-  // // b -> a | b
-  // ...typedFnType(newRight, fnType =>
-  //   makeGeneric((a, b) =>
-  //     fnType
-  //       (b)
-  //       (sumType(() => a)(() => b))
-  //   ), GenericType),
-
-  // // a | b -> (a -> c, b-> c) -> c
-  // ...typedFnType(match, fnType =>
-  //   makeGeneric((a, b, c) =>
-  //     fnType
-  //       (() => sumType(() => a)(() => b))
-  //       (() => fnType
-  //         (() => prodType
-  //           (() => fnType(() => a)(() => c))
-  //           (() => fnType(() => b)(() => c))
-  //         )
-  //         (() => c)
-  //       )
-  //   ), GenericType),
-]};
diff --git a/structures/types.js b/structures/types.js
deleted file mode 100644
index 9a030ff..0000000
--- a/structures/types.js
+++ /dev/null
@@ -1,59 +0,0 @@
-// to break up dependency cycles, type constructors are defined in their own JS module
-
-import { Type } from "../primitives/types.js";
-import { getSymbol, makeTypeConstructor } from "../type_constructor.js";
-
-// Function type
-
-// The registry ensures that we never accidentally create more than one JS object for the same function type.
-// It is a cheap workaround for JS lacking customizable hash-functions and equality-testing-functions.
-// This same pattern is repeated throughout the code for all non-nullary type constructors (list, sum, product, ...)
-export const symbolFunction = Symbol('Function');
-export const fnType = makeTypeConstructor(symbolFunction)(2);
-
-export const isFunction = type => getSymbol(type) === symbolFunction;
-
-// Convenience function. Creates a function type, and also create Type-links for the function type (being typed by Function) and for all the nested function types. Saves a lot of code writing.
-export const typedFnType = (instance, callback, typeOfType = Type) => {
-  const fnTs = [];
-  const wrappedFnType = inType => outType => {
-    const fnT = fnType(() => inType)(() => outType);
-    fnTs.push(fnT);
-    return fnT;
-  };
-  const t = callback(wrappedFnType); // force evaluation
-  if (t.typeVars && typeOfType === Type) {
-    throw new Error("you probably meant to create a GenericType");
-  }
-  const res = [
-    { i: instance, t             },
-    { i: t       , t: typeOfType },
-    // ...fnTs.map(fnT => ({ i: fnT, t: Type })),
-  ];
-  return res;
-};
-
-// Sum type
-
-export const symbolSum = Symbol("Sum");
-export const sumType = makeTypeConstructor(symbolSum)(2);
-
-// Product type
-
-export const symbolProduct = Symbol("Product");
-export const prodType = makeTypeConstructor(symbolProduct)(2);
-
-// List type
-
-export const symbolList = Symbol('List');
-export const lsType = makeTypeConstructor(symbolList)(1);
-
-// Set type
-
-export const symbolSet = Symbol('Set');
-export const setType = makeTypeConstructor(symbolSet)(1);
-
-// Dict type
-
-export const symbolDict = Symbol('Dict');
-export const dictType = makeTypeConstructor(symbolDict)(2);
\ No newline at end of file
diff --git a/type_constructor.js b/type_constructor.js
deleted file mode 100644
index 9fda806..0000000
--- a/type_constructor.js
+++ /dev/null
@@ -1,59 +0,0 @@
-// import { DefaultMap } from "./util/defaultmap.js";
-
-// const nullaryTypeConstructors = new DefaultMap(
-//   // symbol -> 0-ary type constructor (= a type, basically)
-//   symbol => ({
-//     symbol,
-//     params: [],
-//   }));
-
-
-// // nAry: how many more type parameters to take
-// // params: the type params we already took
-// const makeTypeConstructorInternal = (symbol, nAry, params = []) => {
-//   // console.log("n_ary:", n_ary);
-//   if (nAry === 0 || nAry === 0n) {
-//     // a bit dirty, but otherwise OK
-//     if (params.length > 0) {
-//       const result = { symbol, params };
-//       // console.log("result:", result);
-//       return result;
-//     }
-//     else {
-//       const result = nullaryTypeConstructors.getdefault(symbol, true)
-//       // console.log("result:", result);
-//       return result;
-//     }
-//   }
-//   else {
-//     // use DefaultMap, so we only construct every type once (saves memory)
-//     const m = new DefaultMap(typeParam => makeTypeConstructorInternal(symbol, nAry - 1, params.concat([typeParam])));
-//     const fnName = 'make'+symbol.description+'Type';
-//     return {
-//       [fnName]: typeParam => m.getdefault(typeParam, true),
-//     }[fnName];
-//   }
-// };
-
-const __makeTypeConstructor = (symbol, nAry, params) => {
-  if (nAry === 0) {
-    return { symbol, params };
-  }
-  // only for debugging, do we give the function a name
-  const fName = `${symbol.description.toLowerCase()}Type${params.length>0?params.length:''}`;
-  return {
-    [fName]: typeParam => {
-      if (typeof typeParam !== 'function') {
-        throw new Error("all type params must be functions");
-      }
-      return __makeTypeConstructor(symbol, nAry-1, params.concat([typeParam]));
-    }
-  }[fName];
-}
-
-// Creates a new nominal type
-// export const makeTypeConstructor = symbol => nAry => makeTypeConstructorInternal(symbol, nAry);
-export const makeTypeConstructor = symbol => nAry => __makeTypeConstructor(symbol, nAry, []);
-
-export const getSymbol = type => type.symbol;
-export const getParams = type => ({ l: type.params });
diff --git a/typeclasses/eq.js b/typeclasses/eq.js
deleted file mode 100644
index 05b7b4f..0000000
--- a/typeclasses/eq.js
+++ /dev/null
@@ -1,43 +0,0 @@
-import { makeGeneric } from "../generics/generics";
-import { GenericType, SymbolT, Type, Unit } from "../primitives/types";
-import { typedFnType } from "../structures/types";
-import { Bool, Byte, Char, Double, Int } from "../primitives/types";
-import { deepEqual } from "../util/util";
-import { eqDictType } from "./eq_dict";
-
-export const getEq = numDict => numDict.eq;
-
-export const ModuleEq = {l:[
-  // type constructor: Type -> Type
-  ...typedFnType(eqDictType, fnType => fnType(() => Type)(() => Type)),
-
-  // (EqDict a) -> a -> a -> Bool
-  ...typedFnType(getEq, fnType =>
-    makeGeneric(a =>
-      fnType
-        (eqDictType(a))
-        (fnType
-          (a)
-          (fnType
-            (a)
-            (Bool)
-          )
-        )), GenericType),
-]};
-
-// all our data (and types) are encoded such that we can test equality the same way:
-
-const eq = x => y => deepEqual(x,y);
-
-const eqDict = {eq};
-
-export const EqInstances = new Map([
-  [Int    , eqDict],
-  [Bool   , eqDict],
-  [Double , eqDict],
-  [Byte   , eqDict],
-  [Char   , eqDict],
-  [Unit   , eqDict],
-  [Type   , eqDict],
-  [SymbolT, eqDict],
-]);
diff --git a/typeclasses/eq_dict.js b/typeclasses/eq_dict.js
deleted file mode 100644
index 7fbd01f..0000000
--- a/typeclasses/eq_dict.js
+++ /dev/null
@@ -1,4 +0,0 @@
-import { makeTypeConstructor } from "../type_constructor.js";
-
-const eqDictSymbol = Symbol('EqDict');
-export const eqDictType = makeTypeConstructor(eqDictSymbol)(1);
\ No newline at end of file
diff --git a/typeclasses/num.js b/typeclasses/num.js
deleted file mode 100644
index e78f10c..0000000
--- a/typeclasses/num.js
+++ /dev/null
@@ -1,55 +0,0 @@
-import { makeGeneric } from "../generics/generics.js";
-import { addDouble, mulDouble } from "../primitives/double.js";
-import { addInt, mulInt } from "../primitives/int.js";
-import { Type } from "../primitives/types.js";
-import { typedFnType, typedFnType2 } from "../structures/types.js";
-import { Double, Int } from "../primitives/types.js";
-import { numDictType } from "./num_type.js";
-
-export const getAdd  = numDict => numDict.add;
-export const getMul  = numDict => numDict.mul;
-
-// getAdd and getMul have same (generic) type:
-//   NumDict a -> a -> a -> a
-const [getAddMulFnType, typesOfFns] = typedFnType2(fnType =>
-  makeGeneric(a => 
-    fnType
-      (numDictType(a))
-      (fnType
-        (a)
-        (fnType(() => a)(() => a))
-      )));
-
-export const ModuleNum = {l:[
-  ...typedFnType(numDictType, fnType => fnType({in: Type, out: Type})),
-  
-  {i: getAdd, t: getAddMulFnType},
-  {i: getMul, t: getAddMulFnType},
-
-  ...typesOfFns,
-]};
-
-
-const IntNumDict = {
-  add: addInt,
-  mul: mulInt,
-};
-
-const DoubleNumDict = {
-  add: addDouble,
-  mul: mulDouble,
-}
-
-export const ModuleNumInstances = {l:[
-  {i: IntNumDict   , t: numDictType(Int)},
-  {i: DoubleNumDict, t: numDictType(Double)},
-]};
-
-// mapping from type to type class implementation
-// in Haskell, such a mapping is global (for the entire application being compiled), and every type can implement every type class at most once.
-// in Lean, such mappings can be local, and there can be multiple implementations per (type, type class).
-// We have to follow Lean's approach, because in DOPE, there is no such thing as a "global scope". Every dependency is explicit, and type class resolution is just a function that always depends on a specific mapping:
-export const NumInstances = new Map([
-  [Int   , IntNumDict   ],
-  [Double, DoubleNumDict],
-]);
diff --git a/typeclasses/num_dict.js b/typeclasses/num_dict.js
deleted file mode 100644
index bf59390..0000000
--- a/typeclasses/num_dict.js
+++ /dev/null
@@ -1,4 +0,0 @@
-import { makeTypeConstructor } from "../type_constructor.js";
-
-const numDictSymbol = Symbol("NumDict");
-export const numDictType = makeTypeConstructor(numDictSymbol)(1);
diff --git a/typeclasses/show.js b/typeclasses/show.js
deleted file mode 100644
index 9d9b6df..0000000
--- a/typeclasses/show.js
+++ /dev/null
@@ -1,9 +0,0 @@
-import { cart2Str, NPoint2DCartesian, NPoint2DPolar, polar2Str } from "../lib/point.js";
-import { Type } from "../primitives/types.js";
-import { prettyT } from "../structures/types.js";
-
-export const ShowInstances = new Map([
-  [Type             , {show: prettyT}],
-  [NPoint2DCartesian, {show: cart2Str}],
-  [NPoint2DPolar    , {show: polar2Str}],
-]);
diff --git a/typeclasses/show_dict.js b/typeclasses/show_dict.js
deleted file mode 100644
index 83166f0..0000000
--- a/typeclasses/show_dict.js
+++ /dev/null
@@ -1,5 +0,0 @@
-import { makeTypeConstructor } from "../type_constructor.js";
-
-const showDictSymbol = Symbol('ShowDict');
-export const showDictType = makeTypeConstructor(showDictSymbol)(1);
-
diff --git a/util/defaultmap.js b/util/defaultmap.js
deleted file mode 100644
index 6d40c66..0000000
--- a/util/defaultmap.js
+++ /dev/null
@@ -1,18 +0,0 @@
-
-export class DefaultMap {
-  constructor(defaultValue, ...rest) {
-    this.defaultValue = defaultValue;
-    this.m = new Map(rest);
-  }
-  getdefault(key, addToMapping = false) {
-    return this.m.get(key) || (() => {
-      const val = this.defaultValue(key);
-      if (addToMapping)
-        this.m.set(key, val);
-      return val;
-    })();
-  }
-  entries() {
-    return this.m.entries();
-  }
-}
diff --git a/util/util.js b/util/util.js
deleted file mode 100644
index 66cbde6..0000000
--- a/util/util.js
+++ /dev/null
@@ -1,101 +0,0 @@
-import { lsType, setType } from "../structures/types.js";
-import { pretty } from "./pretty.js";
-
-// re-inventing the wheel:
-export function deepEqual(a, b) {
-  if (a === b) return true; // <- shallow equality and primitives
-  if (typeof a !== 'object' || typeof b !== 'object' || a === null || b === null) {
-    return false;
-  }
-  if (Array.isArray(a) && Array.isArray(b)) {
-    if (a.length !== b.length) return false;
-    for (let i = 0; i < a.length; i++) {
-      if (!deepEqual(a[i], b[i])) return false;
-    }
-    return true;
-  }
-  if (a instanceof Set) {
-    if (!(b instanceof Set)) {
-      return false;
-    }
-    if (a.size !== b.size) {
-      return false;
-    }
-    for (const entry of a) {
-      if (!b.has(entry)) {
-        return false;
-      }
-    }
-    return true;
-  }
-  const keysA = Object.keys(a);
-  const keysB = Object.keys(b);
-  if (keysA.length !== keysB.length) return false;
-  for (let key of keysA) {
-    if (!keysB.includes(key) || !deepEqual(a[key], b[key])) {
-      return false;
-    }
-  }
-  return true;
-}
-
-// zip two arrays
-export function zip(a, b) {
-  return a.map((k, i) => [k, b[i]]);
-}
-
-export function capitalizeFirstLetter(val) {
-  return String(val).charAt(0).toUpperCase() + String(val).slice(1);
-}
-
-const _mapRecursiveStructure = mapping => transform => root => {
-  const found = mapping.get(root);
-  if (found) {
-    // already mapped
-    // return existing result to prevent endless recursion
-    return found;
-  }
-  // note the indirection (wrapped in lamda), this allows the user to recursively map the children (which may refer to the root) without yet having finished mapping the root.
-  let memo;
-  const result = () => {
-    // memoization is necessary for correctness
-    return memo || (memo = transform(root, _mapRecursiveStructure(mapping)(transform)));
-  };
-  mapping.set(root, result);
-  return result;
-};
-
-export const mapRecursiveStructure = _mapRecursiveStructure(new Map());
-
-const _transformType = mapping => transform => type => {
-  const found = mapping.get(type);
-  if (found) {
-    return found;
-  }
-  const mapped = transform(type, _transformType(mapping)(transform));
-  mapping.set(type, mapped);
-  return mapped;
-}
-
-export const transformType = _transformType(new Map());
-
-const __memo = () => {
-  let memo;
-  return fn => memo || (memo = fn());
-}
-export const memo = fn => {
-  return __memo()(fn);
-}
-
-// let infiniteSet = mapRecursiveStructure((type, map) => {
-//   const ps = [];
-//   for (const p of type.params) {
-//     ps.push(map(p()));
-//   }
-//   return setType(ps[0]);
-// })(infiniteList)();
-// console.log(infiniteSet);
-// // while (true) {
-// //   console.log(infiniteSet);
-// //   infiniteSet = infiniteSet.params[0]();
-// // }