doc-src/IsarAdvanced/Codegen/Thy/examples/pick2.ML
author berghofe
Wed, 07 May 2008 10:56:52 +0200
changeset 26803 0af0f674845d
parent 26318 967323f93c67
permissions -rw-r--r--
- Explicitely passed pred_subset_eq and pred_equals_eq as an argument to the to_set and to_pred attributes, because it is no longer applied automatically - Manually applied predicate1I in proof of accp_subset, because it is no longer part of the claset - Replaced psubset_def by less_le

structure Nat = 
struct

datatype nat = Suc of nat | Zero_nat;

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;

fun minus_nat (Suc m) (Suc n) = minus_nat m n
  | minus_nat Zero_nat n = Zero_nat
  | minus_nat m Zero_nat = m;

end; (*struct Nat*)

structure Codegen = 
struct

fun pick ((k, v) :: xs) n =
  (if Nat.less_nat n k then v else pick xs (Nat.minus_nat n k));

end; (*struct Codegen*)