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generics/generics.test.js

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+import { Bool, Int } from "../primitives/symbols.js";
+import { fnType, lsType } from "../type_registry.js";
+import { assign, makeGeneric, matchConcrete, matchGeneric } from "./generics.js";
+
+// a -> Int
+const a_to_Int = makeGeneric(a => fnType({in: a, out: Int}));
+// Bool -> Int
+const Bool_to_Int = fnType({in: lsType(Bool), out: Int});
+// should be: Bool -> Int
+console.log(matchConcrete(a_to_Int, Bool_to_Int));
+
+// (a -> a) -> b
+const fnType2 = makeGeneric((a,b) => fnType({in: fnType({in: a, out: a}), out: b}));
+// (Bool -> Bool) -> a
+const fnType3 = makeGeneric(a => fnType({in: fnType({in: Bool, out: Bool}), out: a}));
+// should be: (Bool -> Bool) -> a
+console.log(matchGeneric(fnType2, fnType3));
+
+// (a -> b) -> [a] -> [b]
+const mapFnType = makeGeneric((a,b) =>
+  fnType({
+    in: fnType({in: a, out: b}),
+    out: fnType({in: lsType(a), out: lsType(b)}),
+  }));
+// a -> a
+const idFnType = makeGeneric(a =>
+  fnType({in: a, out: a}));
+// should be: [a] -> [a]
+console.log(assign(mapFnType, idFnType));