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

Theorems for converting between wf and wfP are now declared
as hints.

structure ROOT = 
struct

structure Code_Generator = 
struct

type 'a eq = {Code_Generator__op_eq : 'a -> 'a -> bool};
fun op_eq (A_:'a eq) = #Code_Generator__op_eq A_;

end; (*struct Code_Generator*)

structure List = 
struct

fun memberl A_ x (y :: ys) =
  Code_Generator.op_eq A_ x y orelse memberl A_ x ys
  | memberl A_ x [] = false;

end; (*struct List*)

structure Codegen = 
struct

fun collect_duplicates A_ xs ys (z :: zs) =
  (if List.memberl A_ z xs
    then (if List.memberl A_ z ys then collect_duplicates A_ xs ys zs
           else collect_duplicates A_ xs (z :: ys) zs)
    else collect_duplicates A_ (z :: xs) (z :: ys) zs)
  | collect_duplicates A_ y ys [] = y;

end; (*struct Codegen*)

end; (*struct ROOT*)