doc-src/IsarAdvanced/Codegen/Thy/examples/example.ML

Reintroduce set_interpreter for Collect and op :.
I removed them by accident when removing old code that dealt with the "set" type.
Incidentally, there is still some broken "set" code in Refute that should be fixed (see TODO in refute.ML).

structure Example = 
struct

fun foldl f a [] = a
  | foldl f a (x :: xs) = foldl f (f a x) xs;

fun rev xs = foldl (fn xsa => fn x => x :: xsa) [] xs;

fun list_case f1 f2 (a :: lista) = f2 a lista
  | list_case f1 f2 [] = f1;

datatype 'a queue = AQueue of 'a list * 'a list;

val empty : 'a queue = AQueue ([], [])

fun dequeue (AQueue ([], [])) = (NONE, AQueue ([], []))
  | dequeue (AQueue (xs, y :: ys)) = (SOME y, AQueue (xs, ys))
  | dequeue (AQueue (v :: va, [])) =
    let
      val y :: ys = rev (v :: va);
    in
      (SOME y, AQueue ([], ys))
    end;

fun enqueue x (AQueue (xs, ys)) = AQueue (x :: xs, ys);

end; (*struct Example*)