turn one example into a test + fix bug in type variable substition function
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4 changed files with 148 additions and 102 deletions
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@ -1,97 +0,0 @@
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import { compareTypes } from "../lib/compare/type.js";
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import { makeGeneric, substitute, unify } from "../lib/generics/generics.js";
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import { Double, Int, Unit } from "../lib/primitives/primitive_types.js";
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import { TYPE_VARS } from "../lib/primitives/typevars.js";
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import { fnType, lsType, prodType, sumType, setType } from "../lib/structures/type_constructors.js";
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import { prettyT } from "../lib/util/pretty.js";
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Error.stackTraceLimit = Infinity;
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// some recursive types:
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const listOfSetOfSelf = lsType(self => setType(_ => self));
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const makeLinkedList = elementType => sumType
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(self => prodType
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(_ => elementType)
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(_ => self))
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(_ => Unit);
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const linkedListOfInt = makeLinkedList(Int);
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const linkedListOfDouble = makeLinkedList(Double);
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// some generic types
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const genericFunction = makeGeneric((a,b) => fnType(_ => a)(_ => b));
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const genericLinkedList = makeGeneric(a => makeLinkedList(a));
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// pretty-printing of recursive types:
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console.log(prettyT(listOfSetOfSelf)); // #0[{#0}]
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console.log(prettyT(linkedListOfInt)); // #0((Int ⨯ #0) + Unit)
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console.log(prettyT(genericFunction)); // (a -> b)
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console.log(prettyT(genericLinkedList)); // #0((a ⨯ #0) + Unit)
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// comparison
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console.log(compareTypes(listOfSetOfSelf)(listOfSetOfSelf)) // 0
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console.log(compareTypes(linkedListOfInt)(linkedListOfInt)) // 0
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console.log(compareTypes(linkedListOfInt)(linkedListOfDouble)) // 1
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console.log(compareTypes(linkedListOfDouble)(linkedListOfInt)) // -1
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console.log(compareTypes(linkedListOfDouble)(linkedListOfDouble)) // 0
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console.log(compareTypes(linkedListOfDouble)(listOfSetOfSelf)) // 1
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console.log(compareTypes(listOfSetOfSelf)(linkedListOfDouble)) // -1
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const genericList = makeGeneric(a => lsType(_ => a));
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const intList = lsType(_ => Int);
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console.log(prettyT(genericList)); // [a]
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// substitution of type parameters
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const substituted = substitute(
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genericList,
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new Map([
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[TYPE_VARS[0], Int],
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])
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);
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console.log(prettyT(substituted)); // [Int]
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// substitution (recursive this time)
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console.log("recursive substitution")
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console.log(prettyT(substitute(
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genericLinkedList,
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new Map([
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[TYPE_VARS[0], Int],
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])
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))); // #0((Int ⨯ #0) + Unit)
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// unification (simple case)
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const type = unify(
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genericList,
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makeGeneric(() => intList));
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console.log(prettyT(type)); // [Int]
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// unification (recursive case)
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console.log("complex case...")
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const unified = unify(
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genericLinkedList,
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makeGeneric(() => linkedListOfInt));
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console.log(prettyT(unified)); // #0((Int ⨯ #0) + Unit)
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// unification (strange case)
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const unified2 = unify(
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makeGeneric(() => listOfSetOfSelf),
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genericList,
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);
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console.log(prettyT(unified2)); // #0[{#0}]
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@ -163,17 +163,24 @@ export const unify = (fType, aType) => {
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export const substitute = (type, substitutions, stack=[]) => {
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// console.log('substitute...', {type, substitutions, stack});
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return substitutions.get(getSymbol(type))
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|| {
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const found = substitutions.get(getSymbol(type));
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if (found) {
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return found;
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}
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return {
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symbol: getSymbol(type),
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params: type.params.map(getParam => parent => {
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const param = getParam(stack.length);
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return stack[param]
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|| substitute(param, substitutions, [...stack, parent]);
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const param = getParam(parent);
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if (stack.includes(param)) {
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// param points back up - that's ok - means we don't have to recurse
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return param;
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}
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return substitute(param, substitutions, [...stack, parent]);
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}),
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};
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};
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export const assignFn = (funType, paramType) => {
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[funType, paramType] = recomputeTypeVars([funType, paramType]);
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// console.log(prettyT(funType), prettyT(paramType));
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136
tests/recursive_types.js
Normal file
136
tests/recursive_types.js
Normal file
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@ -0,0 +1,136 @@
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import assert from "node:assert";
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import { compareTypes } from "../lib/compare/type.js";
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import { makeGeneric, substitute, unify } from "../lib/generics/generics.js";
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import { Double, Int, Unit } from "../lib/primitives/primitive_types.js";
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import { UNBOUND_SYMBOLS } from "../lib/primitives/typevars.js";
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import { fnType, lsType, prodType, sumType, setType } from "../lib/structures/type_constructors.js";
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import { prettyT } from "../lib/util/pretty.js";
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// some recursive types:
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const listOfSetOfSelf = lsType(self => setType(_ => self));
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const makeLinkedList = elementType =>
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sumType
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(self => prodType
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(_ => elementType)
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(_ => self))
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(_ => Unit);
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const linkedListOfInt = makeLinkedList(Int);
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const linkedListOfDouble = makeLinkedList(Double);
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// some generic types
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const genericFunction = makeGeneric((a,b) => fnType(_ => a)(_ => b));
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const genericLinkedList = makeGeneric(a => makeLinkedList(a));
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// pretty-printing of recursive types:
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assert.equal(
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prettyT(listOfSetOfSelf),
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"#0[{#0}]",
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);
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assert.equal(
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prettyT(linkedListOfInt),
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"#0((Int ⨯ #0) + Unit)",
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);
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assert.equal(
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prettyT(genericFunction),
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"(a -> b)",
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);
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assert.equal(
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prettyT(genericLinkedList),
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"#0((a ⨯ #0) + Unit)",
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);
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// comparison
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assert.equal(
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compareTypes(listOfSetOfSelf)(listOfSetOfSelf),
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0,
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"types should be equal",
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);
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assert.equal(
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compareTypes(linkedListOfInt)(linkedListOfInt),
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0,
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"types should be equal",
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);
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assert.notEqual(
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compareTypes(linkedListOfInt)(linkedListOfDouble),
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0,
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"types should not be equal",
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);
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assert.equal(
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compareTypes(linkedListOfDouble)(linkedListOfInt)
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+ compareTypes(linkedListOfInt)(linkedListOfDouble),
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0,
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"comparison invariant",
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);
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assert.equal(
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compareTypes(linkedListOfDouble)(linkedListOfDouble),
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0,
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"types should be equal",
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)
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assert.notEqual(
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compareTypes(linkedListOfDouble)(listOfSetOfSelf),
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0,
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"types should not be equal",
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);
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assert.equal(
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compareTypes(linkedListOfDouble)(listOfSetOfSelf)
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+ compareTypes(listOfSetOfSelf)(linkedListOfDouble),
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0,
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"comparison invariant",
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);
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const genericList = makeGeneric(a => lsType(_ => a));
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// substitution of type parameters
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assert.equal(
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// actual
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prettyT(substitute(
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genericLinkedList,
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new Map([
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[UNBOUND_SYMBOLS[0], Int],
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])
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)),
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// expected
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"#0((Int ⨯ #0) + Unit)",
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);
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// unification (recursive)
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assert.equal(
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// actual
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prettyT(unify(
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genericLinkedList,
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makeGeneric(() => linkedListOfInt)
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)),
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// expected
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"#0((Int ⨯ #0) + Unit)",
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)
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assert.equal(
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// actual
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prettyT(unify(
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makeGeneric(() => listOfSetOfSelf),
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genericList,
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)),
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// expected
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"#0[{#0}]",
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)
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