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

added logic-specific sessions;

structure HOL = 
struct

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

fun eqop A_ a = eq A_ a;

end; (*struct HOL*)

structure List = 
struct

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

fun member A_ x (y :: ys) =
  (if HOL.eqop A_ y x then true else member A_ x ys)
  | member A_ x [] = false;

end; (*struct List*)

structure Set = 
struct

datatype 'a set = Set of 'a list;

val empty : 'a set = Set [];

fun insert x (Set xs) = Set (x :: xs);

fun uniona xs (Set ys) = List.foldr insert ys xs;

fun member A_ x (Set xs) = List.member A_ x xs;

fun unionaa (Set xs) = List.foldr uniona xs empty;

end; (*struct Set*)