structure ROOT =
struct
structure Orderings =
struct
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_;
end; (*struct Orderings*)
structure Code_Generator =
struct
type 'a eq = {eq : 'a -> 'a -> bool};
fun eq (A_:'a eq) = #eq A_;
end; (*struct Code_Generator*)
structure Nat =
struct
datatype nat = Zero_nat | Suc of nat;
fun eq_nat Zero_nat (Suc m) = false
| eq_nat (Suc n) Zero_nat = false
| eq_nat (Suc n) (Suc m) = eq_nat n m
| eq_nat Zero_nat Zero_nat = true;
val eq_nata = {eq = eq_nat} : nat Code_Generator.eq;
fun less_nat n (Suc m) = less_eq_nat n m
| less_nat n Zero_nat = false
and less_eq_nat (Suc n) m = less_nat n m
| less_eq_nat Zero_nat m = true;
val ord_nat = {less_eq = less_eq_nat, less = less_nat} :
nat Orderings.ord;
end; (*struct Nat*)
structure Codegen =
struct
datatype ('a, 'b) searchtree = Leaf of 'a * 'b |
Branch of ('a, 'b) searchtree * 'a * ('a, 'b) searchtree;
fun update (C1_, C2_) (it, entry) (Branch (t1, key, t2)) =
(if Orderings.less_eq C2_ it key
then Branch (update (C1_, C2_) (it, entry) t1, key, t2)
else Branch (t1, key, update (C1_, C2_) (it, entry) t2))
| update (C1_, C2_) (it, entry) (Leaf (key, vala)) =
(if Code_Generator.eq C1_ it key then Leaf (key, entry)
else (if Orderings.less_eq C2_ it key
then Branch (Leaf (it, entry), it, Leaf (key, vala))
else Branch (Leaf (key, vala), it, Leaf (it, entry))));
val example : (Nat.nat, (Nat.nat list)) searchtree =
update (Nat.eq_nata, Nat.ord_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.ord_nat)
(Nat.Suc (Nat.Suc (Nat.Suc Nat.Zero_nat)),
[Nat.Suc (Nat.Suc (Nat.Suc Nat.Zero_nat))])
(update (Nat.eq_nata, Nat.ord_nat)
(Nat.Suc (Nat.Suc Nat.Zero_nat), [Nat.Suc (Nat.Suc Nat.Zero_nat)])
(Leaf (Nat.Suc Nat.Zero_nat, []))));
end; (*struct Codegen*)
end; (*struct ROOT*)