--- a/src/Pure/General/integer.ML Fri Nov 03 17:27:00 2017 +0100
+++ b/src/Pure/General/integer.ML Fri Nov 03 19:16:41 2017 +0100
@@ -51,7 +51,7 @@
in if r = 0 then l' else l' * l end;
in
if k < 0
- then error "pow: negative exponent"
+ then IntInf.pow (l, k)
else pw k l
end;