branching and very basic merging of slots

scripts/generics.js

@@ -0,0 +1,42 @@
+import { Bool, Int } from "../primitives/types.js";
+import { fnType, lsType, prettyT } from "../structures/types.js";
+import { assign, makeGeneric, unify } from "../generics/generics.js";
+
+// a -> Int
+const a_to_Int = makeGeneric(a => fnType(a)(Int));
+// Bool -> Int
+const Bool_to_Int = makeGeneric(() => fnType(lsType(Bool))(Int));
+console.log("should be: [Bool] -> Int")
+console.log(prettyT(unify(a_to_Int, Bool_to_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)));
+
+// (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)));
+
+// (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)));