doc-src/Codegen/Thy/examples/tree.ML

clarified

structure HOL = 
struct

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

type 'a ord = {less_eq : 'a -> 'a -> bool, less : 'a -> 'a -> bool};
fun less_eq (A_:'a ord) = #less_eq A_;
fun less (A_:'a ord) = #less A_;

fun eqop A_ a = eq A_ a;

end; (*struct HOL*)

structure Orderings = 
struct

type 'a preorder = {Orderings__ord_preorder : 'a HOL.ord};
fun ord_preorder (A_:'a preorder) = #Orderings__ord_preorder A_;

type 'a order = {Orderings__preorder_order : 'a preorder};
fun preorder_order (A_:'a order) = #Orderings__preorder_order A_;

type 'a linorder = {Orderings__order_linorder : 'a order};
fun order_linorder (A_:'a linorder) = #Orderings__order_linorder A_;

end; (*struct Orderings*)

structure Nat = 
struct

datatype nat = Suc of nat | Zero_nat;

fun eq_nat (Suc a) Zero_nat = false
  | eq_nat Zero_nat (Suc a) = false
  | eq_nat (Suc nat) (Suc nat') = eq_nat nat nat'
  | eq_nat Zero_nat Zero_nat = true;

val eq_nata = {eq = eq_nat} : nat HOL.eq;

fun less_nat m (Suc n) = less_eq_nat m n
  | less_nat n Zero_nat = false
and less_eq_nat (Suc m) n = less_nat m n
  | less_eq_nat Zero_nat n = true;

val ord_nat = {less_eq = less_eq_nat, less = less_nat} : nat HOL.ord;

val preorder_nat = {Orderings__ord_preorder = ord_nat} :
  nat Orderings.preorder;

val order_nat = {Orderings__preorder_order = preorder_nat} :
  nat Orderings.order;

val linorder_nat = {Orderings__order_linorder = order_nat} :
  nat Orderings.linorder;

end; (*struct Nat*)

structure Codegen = 
struct

datatype ('a, 'b) searchtree =
  Branch of ('a, 'b) searchtree * 'a * ('a, 'b) searchtree |
  Leaf of 'a * 'b;

fun update (A1_, A2_) (it, entry) (Leaf (key, vala)) =
  (if HOL.eqop A1_ it key then Leaf (key, entry)
    else (if HOL.less_eq
               ((Orderings.ord_preorder o Orderings.preorder_order o
                  Orderings.order_linorder)
                 A2_)
               it key
           then Branch (Leaf (it, entry), it, Leaf (key, vala))
           else Branch (Leaf (key, vala), it, Leaf (it, entry))))
  | update (A1_, A2_) (it, entry) (Branch (t1, key, t2)) =
    (if HOL.less_eq
          ((Orderings.ord_preorder o Orderings.preorder_order o
             Orderings.order_linorder)
            A2_)
          it key
      then Branch (update (A1_, A2_) (it, entry) t1, key, t2)
      else Branch (t1, key, update (A1_, A2_) (it, entry) t2));

val example : (Nat.nat, (Nat.nat list)) searchtree =
  update (Nat.eq_nata, Nat.linorder_nat)
    (Nat.Suc (Nat.Suc (Nat.Suc (Nat.Suc Nat.Zero_nat))),
      [Nat.Suc (Nat.Suc Nat.Zero_nat), Nat.Suc (Nat.Suc Nat.Zero_nat)])
    (update (Nat.eq_nata, Nat.linorder_nat)
      (Nat.Suc (Nat.Suc (Nat.Suc Nat.Zero_nat)),
        [Nat.Suc (Nat.Suc (Nat.Suc Nat.Zero_nat))])
      (update (Nat.eq_nata, Nat.linorder_nat)
        (Nat.Suc (Nat.Suc Nat.Zero_nat), [Nat.Suc (Nat.Suc Nat.Zero_nat)])
        (Leaf (Nat.Suc Nat.Zero_nat, []))));

end; (*struct Codegen*)