add examples

1 files changed, 36 insertions, 0 deletions

diff --git a/examples/mapper.ts b/examples/mapper.ts
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+/*
+If you've ever said "I wish generic types were first class," you're probably doing something wrong.
+On the other hand, you might be doing something right! KaiScript makes this possible.
+*/
+
+import { CallFn, Evaluate, FnPrim, Lex, Parse } from "../src";
+
+// You might have a type that looks like this
+type MyGenericMapper<T extends number> = `${T}`;
+// And another that looks like this
+type MyGenericMapper2<T extends number> = `number:${T}`;
+
+// And another type that wants to consume them
+//@ts-expect-error
+type Map5<Mapper> = Mapper<5>;
+
+// Hmm, can't do that. ...maybe this?
+type Map5_2<Mapper extends <T extends number>() => string> = ReturnType<
+  //@ts-expect-error
+  Mapper<5>
+>;
+
+// But with KaiScript:
+
+type MyKaiScriptMapper = Evaluate<Parse<Lex<"fn(n, tostring(n))">>>[0];
+type MyKaiScriptMapper2 = Evaluate<
+  Parse<Lex<'fn(n, tostring(add("number:", tostring(n))))'>>
+>[0];
+
+type Map5KaiScript<Mapper extends FnPrim> = CallFn<Mapper, [5]>;
+// "5"
+type Mapped1 = Map5KaiScript<MyKaiScriptMapper>;
+// "number:5"
+type Mapped2 = Map5KaiScript<MyKaiScriptMapper2>;
+
+// KaiScript lets you get an extra order of primitivity out of your types