author haftmann Mon, 20 Apr 2009 09:32:09 +0200 changeset 30953 d5f5ab29d769 parent 30952 7ab2716dd93b child 30954 cf50e67bc1d1
yield is now a static ML function
```--- a/src/HOL/ex/Predicate_Compile.thy	Mon Apr 20 09:32:07 2009 +0200
+++ b/src/HOL/ex/Predicate_Compile.thy	Mon Apr 20 09:32:09 2009 +0200
@@ -12,26 +12,21 @@
| "next yield (Predicate.Join P xq) = (case yield P
of None \<Rightarrow> next yield xq | Some (x, Q) \<Rightarrow> Some (x, Predicate.Seq (\<lambda>_. Predicate.Join Q xq)))"

-ML {*
-let
-  fun yield (@{code Predicate.Seq} f) = @{code next} yield (f ())
-in
-  yield @{code "\<bottom> :: 'a Predicate.pred"} (*replace bottom with sequence to evaluate*)
-end
-*}
-
fun anamorph :: "('b \<Rightarrow> ('a \<times> 'b) option) \<Rightarrow> index \<Rightarrow> 'b \<Rightarrow> 'a list \<times> 'b" where
"anamorph f k x = (if k = 0 then ([], x)
else case f x of None \<Rightarrow> ([], x) | Some (v, y) \<Rightarrow> let (vs, z) = anamorph f (k - 1) y in (v # vs, z))"

ML {*
-let
-  fun yield (@{code Predicate.Seq} f) = @{code next} yield (f ())
-  fun yieldn k = @{code anamorph} yield k
-in
-  yieldn 0 (*replace with number of elements to retrieve*)
-    @{code "\<bottom> :: 'a Predicate.pred"} (*replace bottom with sequence to evaluate*)
-end
+structure Predicate =
+struct
+
+open Predicate;
+
+fun yield (Predicate.Seq f) = @{code next} yield (f ());
+
+fun yieldn k = @{code anamorph} yield k;
+
+end;
*}

end
\ No newline at end of file```