# HG changeset patch
# User nipkow
# Date 1499533422 -7200
# Node ID d2283b15d2caf4ff26bf3f88a883ca70f8be981d
# Parent  0c9bba1e8e97fdbd764bd6b9055dc37de5b8592f
.

diff -r 0c9bba1e8e97 -r d2283b15d2ca Exercises/ex12/ex12.thy
--- a/Exercises/ex12/ex12.thy	Fri Jul 07 21:00:57 2017 +0200
+++ b/Exercises/ex12/ex12.thy	Sat Jul 08 19:03:42 2017 +0200
@@ -24,6 +24,9 @@
 fun deq :: "'a queue \<Rightarrow> 'a queue" where
 "deq (xs,ys) = balance (xs, tl ys)"
 
+text \<open>Note that we assume that the size computation in \<open>balance\<close> only takes constant time.
+In reality the time is linear. How would you avoid that?\<close>
+
 fun t_enq :: "'a \<Rightarrow> 'a queue \<Rightarrow> nat" where
 "t_enq a (xs,ys) = 1 + (if size xs + 1 \<le> size ys then 0 else size xs + 1 + size ys)"