update examples and add documentation

08-type-programming/main.ts

@@ -1,3 +1,9 @@
+// This recursively matches path segments and parameters in segments which
+// are surrounded by curly braces (i.e. `{foo}`) in these segments.
+// The results are joined to a superset of objects with their params
+// via the `&`.
+// In example, the path /{foo}/{bar} results in the type
+// `{ foo: string } & { bar: string }`
 type ParseUrlParamsRaw<Url> = Url extends `${infer Start}/${infer Rest}`
   ? ParseUrlParamsRaw<Start> & ParseUrlParamsRaw<Rest>
   : Url extends `{${infer Param}}`
@@ -20,4 +26,5 @@ function navigate<P extends string>(path: P, params: ParseUrlParams<P>) {
 function main() {
   navigate("/hello", {});
   navigate("/hello/{name}", { name: "foo" });
+  navigate("/book/{author}/{id}", { author: "foo", id: "bar" });
 }