progress with type classes, type inference still very ad-hoc

generics/generics.js

@@ -1,6 +1,7 @@
 import { lsType } from "../structures/list_common.js";
 import { fnType } from "../metacircular.js";
-import { deepEqual, pretty } from "../util.js";
+import { deepEqual, DefaultMap, pretty } from "../util.js";
+import { numDictType } from "../typeclasses/num_type.js";
 
 const genericTypeRegistry = new DefaultMap(underlyingType => ({ generic: underlyingType }));
 
@@ -31,7 +32,7 @@ export const makeGeneric = callback => {
 };
 
 // From the given set of type variables, return only those that occur in the given type.
-const occurring = (type, typeVars) => {
+export const occurring = (type, typeVars) => {
   if (typeVars.has(type)) {
     return new Set([type]);
   }
@@ -130,9 +131,24 @@ export const unify = (
   }
 
   if (formalType.numDict !== undefined) {
-
+    if (actualType.numDict === undefined) {
+      throw new Error(`cannot assign ${pretty(actualType)} to ${pretty(formalType)}`);
     }
-  throw new Error("i don't know what to do :(")
+    else {
+      // both are NumDict type
+      const underlyingType = unify(
+        {typeVars: formalTypeVars, type: formalType.numDict},
+        {typeVars: actualTypeVars, type: actualType.numDict});
+      return {
+        substitutions: underlyingType.substitutions,
+        typeVars: new Set([
+          ...actualTypeVars,
+          ...formalTypeVars].filter(a => !underlyingType.substitutions.has(a))),
+        type: numDictType(underlyingType.type),
+      };
+    }
+  }
+  throw new Error("i don't know what to do :(");
 };
 
 // export const matchConcrete = ({typeVars, type: formalType}, actualType) => {
@@ -167,4 +183,4 @@ export const assign = (genFnType, paramType) => {
     typeVars: matchedInType.typeVars,
     type: substitutedOutType,
   };
-}
+};

generics/types.js

@@ -0,0 +1,2 @@
+
+

metacircular.js

@@ -53,7 +53,6 @@ export const typedFnType = (instance, callback) => {
 export const typedFnType2 = callback => {
   const fnTs = [];
   const wrappedFnType = ({ in: inType, out: outType }) => {
-    console.log('wrappedFnType called');
     const fnT = fnType({ in: inType, out: outType });
     fnTs.push(fnT);
     return fnT;

package.json

@@ -1,4 +1,5 @@
 {
+	"type": "module",
 	"dependencies": {
 		"@inquirer/prompts": "^7.4.0"
 	}

structures/sum.js

@@ -1,8 +1,8 @@
-import { sumType } from "../type_registry.js";
 import { prodType } from "./product.js";
 import { fnType } from "../metacircular.js";
 import { Function, Type } from "../metacircular.js";
 import { Module } from "./list_types/module.js";
+import { DefaultMap } from "../util.js";
 
 const sumTypeRegistry = new DefaultMap(leftType => new DefaultMap(rightType => ({ operator: "sum", leftType, rightType })));
 

typeclasses/num.js

@@ -1,10 +1,9 @@
-import { makeGeneric } from "../generics/generics";
-import { addDouble, mulDouble } from "../primitives/double";
-import { addInt, mulInt } from "../primitives/int";
-import { typedFnType, typedFnType2 } from "../metacircular";
-
-const numDictTypeRegistry = new DefaultMap(a => ({numDict: a}));
-export const numDictType = a => numDictTypeRegistry.getdefault(a, true);
+import { makeGeneric } from "../generics/generics.js";
+import { addDouble, mulDouble } from "../primitives/double.js";
+import { addInt, mulInt } from "../primitives/int.js";
+import { Type, typedFnType, typedFnType2 } from "../metacircular.js";
+import { Double, Int } from "../primitives/symbols.js";
+import { numDictType } from "./num_type.js";
 
 export const getAdd  = numDict => numDict.add;
 export const getMul  = numDict => numDict.mul;
@@ -40,8 +39,8 @@ const DoubleNumDict = {
 }
 
 export const ModuleNumInstances = {l:[
-  {i: IntNumDict   , t: NumDict},
-  {i: DoubleNumDict, t: NumDict},
+  {i: IntNumDict   , t: numDictType(Int)},
+  {i: DoubleNumDict, t: numDictType(Double)},
 ]};
 
 // mapping from type to type class implementation

typeclasses/num.test.js

@@ -0,0 +1,23 @@
+import { assign } from "../generics/generics.js";
+import { makeGeneric } from "../generics/generics.js";
+import { fnType } from "../metacircular.js";
+import { Double, Int } from "../primitives/symbols.js";
+import { numDictType } from "./num_type.js";
+
+const square = numDict => x => getMul(numDict)(x)(x);
+
+const squareFnType = makeGeneric(a => 
+  fnType({
+    in: numDictType(a),
+    out: fnType({
+      in: a,
+      out: a,
+    }),
+  }));
+
+// should be: Int -> Int
+console.log(assign(squareFnType, makeGeneric(() => numDictType(Int))));
+
+// should be: Double -> Double
+console.log(assign(squareFnType, makeGeneric(() => numDictType(Double))));
+

typeclasses/num_type.js

@@ -0,0 +1,4 @@
+import { DefaultMap } from "../util.js";
+
+const numDictTypeRegistry = new DefaultMap(a => ({ numDict: a }));
+export const numDictType = a => numDictTypeRegistry.getdefault(a, true);

typeclasses/resolve.js

@@ -0,0 +1 @@
+// const resolveTypeClass = (mapping, )