From e11fba95487b625e3a81145fe278a091a9662d6d Mon Sep 17 00:00:00 2001
From: James Mitchell <jdm3@st-and.ac.uk>
Date: Mon, 1 Jan 2018 15:04:25 +0000
Subject: [PATCH] Fix PositionProperty with from < 1

---
 lib/list.gi              |  8 ++++----
 tst/testinstall/list.tst | 20 ++++++++++++++++++++
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/lib/list.gi b/lib/list.gi
index acfad272058..362b250674e 100644
--- a/lib/list.gi
+++ b/lib/list.gi
@@ -1525,8 +1525,8 @@ InstallMethod( PositionProperty,
     function( list, func, from )
     local i;
 
-    if from < 1 then
-      from:= 1;
+    if from < 0 then
+      from:= 0;
     fi;
     for i in [ from+1 .. Length( list ) ] do
       if IsBound( list[i] ) then
@@ -1557,8 +1557,8 @@ InstallMethod( PositionProperty,
     function( list, func, from )
     local i;
 
-    if from < 1 then
-      from:= 1;
+    if from < 0 then
+      from:= 0;
     fi;
     for i in [ from+1 .. Length( list ) ] do
       if func( list[i] ) then
diff --git a/tst/testinstall/list.tst b/tst/testinstall/list.tst
index 95d4f6e07a4..743c1008b4f 100644
--- a/tst/testinstall/list.tst
+++ b/tst/testinstall/list.tst
@@ -209,5 +209,25 @@ gap> PositionsProperty( ll, ReturnTrue );
 gap> PositionsProperty( ll, IsInt );
 [ 1, 2, 3 ]
 
+# PositionProperty
+gap> ll := [ 1, , "s" ];;
+gap> PositionProperty( ll, ReturnTrue, 0);
+1
+gap> PositionProperty( ll, ReturnTrue, 1);
+3
+gap> PositionProperty( ll, IsInt, 0);
+1
+gap> PositionProperty( ll, IsInt, 1);
+fail
+gap> ll := [ 1, 2, 3 ];;
+gap> PositionProperty( ll, ReturnTrue, 0);
+1
+gap> PositionProperty( ll, ReturnTrue, 1);
+2
+gap> PositionProperty( ll, ReturnTrue, 2);
+3
+gap> PositionProperty( ll, ReturnTrue, 3);
+fail
+
 #
 gap> STOP_TEST("list.tst");