From 155f114b824731d5672775a88d01be4fae52f051 Mon Sep 17 00:00:00 2001
From: Chris Jefferson <caj21@st-andrews.ac.uk>
Date: Tue, 21 Feb 2017 13:20:44 +0000
Subject: [PATCH] Test recursion level altered consistently.

---
 tst/testinstall/tilde.tst | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/tst/testinstall/tilde.tst b/tst/testinstall/tilde.tst
index 9290c5827d4..37d08da8915 100644
--- a/tst/testinstall/tilde.tst
+++ b/tst/testinstall/tilde.tst
@@ -46,4 +46,34 @@ Syntax error: ~ is not a valid name for an argument in stream:1
  ^
 gap> ({} -> ~);
 function(  ) ... end
+gap> list1 := [1,~];
+[ 1, ~ ]
+gap> list2 := [1,[1,[1,[1,0]]]];
+[ 1, [ 1, [ 1, [ 1, 0 ] ] ] ]
+
+# Check that the RecursionDepth counter in the kernel is incremented and
+# decremented correctly. If it isn't decremented correctly, then it will
+# eventually exceed the `RecursionTrapInterval` (which normally is
+# 5000), and the test will fail due to an unexpected error message.
+gap> ForAny([1..10000], x -> (list1 = list2));
+false
+gap> ForAny([1..10000], x -> (list1 < list2));
+false
+gap> ForAny([1..10000], x -> (list1 <= list2));
+false
+gap> ForAll([1..10000], x -> (list1 <> list2));
+true
+gap> rec1 := rec( x := ~ );
+rec( x := ~ )
+gap> rec2 := rec( x := rec( x := rec( x := rec( x := rec( x := rec() ) ) ) ) );
+rec( x := rec( x := rec( x := rec( x := rec( x := rec(  ) ) ) ) ) )
+gap> ForAny([1..10000], q -> (rec1 = rec2));
+false
+gap> ForAll([1..10000], q -> (rec1 <> rec2));
+true
+
+# This can be different every time GAP starts
+gap> bool := (rec1 < rec2);;
+gap> ForAll([1..10000], q -> ( (rec1 < rec2) = bool) );
+true
 gap> STOP_TEST( "tilde.tst", 1);