--- a/src/Pure/Concurrent/lazy.ML Thu Mar 17 16:56:44 2016 +0100
+++ b/src/Pure/Concurrent/lazy.ML Fri Mar 18 16:26:35 2016 +0100
@@ -99,7 +99,16 @@
if is_finished x then Future.value_result (force_result x)
else (singleton o Future.forks) params (fn () => force x);
+
+(* toplevel pretty printing *)
+
+val _ =
+ PolyML.addPrettyPrinter (fn depth => fn pretty => fn x =>
+ (case peek x of
+ NONE => PolyML.PrettyString "<lazy>"
+ | SOME (Exn.Exn _) => PolyML.PrettyString "<failed>"
+ | SOME (Exn.Res y) => pretty (y, depth)));
+
end;
type 'a lazy = 'a Lazy.lazy;
-