add nominal types for 2D points

generics/generics.js

@@ -15,6 +15,7 @@ export const makeGeneric = callback => {
   };
 };
 
+// From the given set of type variables, return only those that occur in the given type.
 const occurring = (type, typeVars) => {
   if (typeVars.has(type)) {
     return new Set([type]);
@@ -36,7 +37,8 @@ const occurring = (type, typeVars) => {
 
 // merge {i: [1], t: List_of_Int} -> 
 
-
+// Thanks to Hans for pointing out that this algorithm exactly like "Unification" in Prolog:
+//  https://www.dai.ed.ac.uk/groups/ssp/bookpages/quickprolog/node12.html
 export const matchGeneric = (
   {typeVars: formalTypeVars, type: formalType},
   {typeVars: actualTypeVars, type: actualType},

lib/point.js

@@ -0,0 +1,57 @@
+import { Function, Type } from "../metacircular.js";
+import { Double } from "../primitives/symbols.js";
+import { nominalType, NominalType } from "../structures/nominal_type.js";
+import { fnType, prodType, typedFnType } from "../type_registry.js";
+
+const PointCartesian2D = nominalType(
+  // just a unique number, to make sure that our type is only equal to itself
+  BigInt("0xBBAAD62B10EE21993BA690A732DA2A6875CE4B6F5E7139D5AEC9FD887F9D24A8"))
+  (prodType(Double, Double));
+
+const PointPolar2D = nominalType(
+  // just a unique number, to make sure that our type is only equal to itself
+  BigInt("0x31CDAB4B3D84C4EB27D3C111FD7580E533268B72E05BD694F8B262913E018B72"))
+  (prodType(Double, Double));
+
+export const cart2polar = ({left: x, right: y}) => {
+  const r = Math.sqrt(x*x + y*y);
+  const θ = Math.atan(y/x);
+  return {left: r, right: θ};
+};
+
+export const polar2cart = ({left: r, right: θ}) => {
+  const x = r * Math.cos(θ);
+  const y = r * Math.sin(θ);
+  return {left: x, right: y};
+}
+
+export const translate = dx => dy => ({left: x, right: y}) => {
+  return {left: x+dx, right: y+dy};
+}
+
+export const rotate = dθ => ({left: r, right: θ}) => {
+  return {left: r, right: θ+dθ};
+}
+
+export const scale = dr => ({left: r, right: θ}) => {
+  return {left: r+dr, right: θ};
+}
+
+export const ModulePoint = {l:[
+  {i: -1                 , t: Double},
+  {i: 2                  , t: Double},
+  {i: {left: 1, right: 2}, t: PointCartesian2D},
+
+  {i: PointCartesian2D   , t: NominalType},
+  {i: PointPolar2D       , t: NominalType},
+
+  ...typedFnType(cart2polar, fnType => fnType({in: PointCartesian2D, out: PointPolar2D})),
+
+  ...typedFnType(polar2cart, fnType => fnType({in: PointPolar2D, out: PointCartesian2D})),
+
+  ...typedFnType(translate , fnType => fnType({in: Double, out: fnType({in: Double, out: fnType({in: PointCartesian2D, out: PointCartesian2D})})})),
+
+  ...typedFnType(rotate, fnType => fnType({in: Double, out: fnType({in: PointPolar2D, out: PointPolar2D})})),
+
+  ...typedFnType(scale, fnType => fnType({in: Double, out: fnType({in: PointPolar2D, out: PointPolar2D})})),
+]};

main.js

@@ -100,29 +100,31 @@ const ModuleValues = {l:[
   {i: {variant: "L", value: 100n}, t: sumType(Int, Bool)},
 ]};
 
+import { select } from '@inquirer/prompts';
+import { ModulePoint } from "./lib/point.js";
+
 
 const ctx = new Context({l:[
-  ...ModuleMetaCircular.l,
-  ...ModuleTyped.l,
-  // ...ModuleConformable,
-  // ...ModuleConformanceCheckConforms,
-  // ...ModuleNum,
-  // ...ModuleEq,
-  ...ModuleBool.l,
-  ...ModuleInt.l,
-  ...ModuleDouble.l,
-  // ...ModuleSquare,
-  // ...ModuleList,
-  ...makeIdFn(Int).l,
-  ...makeSquare({i: mulInt, t: Int_to_Int_to_Int}).l,
-  ...makeSquare({i: mulDouble, t: Double_to_Double_to_Double}).l,
-  ...ModuleList.l,
-  ...ModuleValues.l,
-  ...ModuleModule.l,
+  // ...ModuleMetaCircular.l,
+  // ...ModuleTyped.l,
+  // // ...ModuleConformable,
+  // // ...ModuleConformanceCheckConforms,
+  // // ...ModuleNum,
+  // // ...ModuleEq,
+  // ...ModuleBool.l,
+  // ...ModuleInt.l,
+  // ...ModuleDouble.l,
+  // // ...ModuleSquare,
+  // // ...ModuleList,
+  // ...makeIdFn(Int).l,
+  // ...makeSquare({i: mulInt, t: Int_to_Int_to_Int}).l,
+  // ...makeSquare({i: mulDouble, t: Double_to_Double_to_Double}).l,
+  // ...ModuleList.l,
+  // ...ModuleValues.l,
+  // ...ModuleModule.l,
+  ...ModulePoint.l,
 ]});
 
-import { input, select } from '@inquirer/prompts';
-
 const makeChoice = ([i, t]) => {
   return {
     value: {i, t: t[0]},

structures/nominal_type.js

@@ -0,0 +1,14 @@
+import { Type } from "../metacircular.js";
+import { Int } from "../primitives/symbols.js";
+import { prodType } from "../type_registry.js";
+import { makeProductType } from "./product.js";
+
+export const NominalType = prodType(Int, Type);
+
+export const ModuleNominalType = makeProductType(Int, Type);
+
+export const nominalType = x => {
+  const result = ModuleNominalType.l[5].i(x); // dirty!!
+  result.__proto__.toString = () => "HEY";
+  return result;
+}

type_registry.js

@@ -2,6 +2,7 @@
 // Maybe we shouldn't use Symbols for types, but we also cannot use primitive values for types because they may accidentally overlap with 'real' values (that are not types)
 // We also cannot use objects for types because similar to Symbols, objects are only equal to themselves if we use them as Map keys.
 
+import { Function } from "./metacircular.js";
 import { DefaultMap } from "./util.js";
 
 // Global store of function types:
@@ -18,6 +19,19 @@ export const fnType = ({in: inType, out: outType}) => {
   }
 };
 
+export const typedFnType = (instance, callback) => {
+  const fnTs = [];
+  const wrappedFnType = ({in: inType, out: outType}) => {
+    const fnT = fnType({in: inType, out: outType});
+    fnTs.push(fnT);
+    return fnT;
+  }
+  return [
+    {i: instance, t: callback(wrappedFnType)},
+    ...fnTs.map(fnT => ({i: fnT, t: Function})),
+  ];
+}
+
 // Global store of list types:
 const listTypes = new Map();
 export const lsType = (elementType) => {

util.js

@@ -45,5 +45,5 @@ export class DefaultMap {
 import { inspect } from 'node:util';
 
 export function pretty(obj) {
-  return inspect(obj, {colors: true});
+  return inspect(obj, {colors: true, depth: null});
 }