From f57d7267ac54ac6f942a74c6da78d034b9f013ad Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Glen=20M=C3=A9vel?= <glen.mevel@crans.org>
Date: Mon, 25 Apr 2016 11:39:03 +0200
Subject: [PATCH] bug fix for CCList.range_by

---
 src/core/CCList.ml | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/src/core/CCList.ml b/src/core/CCList.ml
index 975a0861..80b8578f 100644
--- a/src/core/CCList.ml
+++ b/src/core/CCList.ml
@@ -793,23 +793,29 @@ module Idx = struct
 end
 
 let range_by ~step i j =
-  if step = 0 then raise (Invalid_argument "CCList.range_by");
-  let rec up i j acc =
-    if i>j then acc else up i (j-step) (j::acc)
-  and down i j acc =
-    if i<j then acc else down i (j-step) (j::acc)
+  let rec range i j acc =
+    if i=j then i::acc else range i (j-step) (j::acc)
   in
-  let j = (j - i) / step * step + i in
-  if step > 0 then up i j [] else down i j []
+  if step = 0 then
+    raise (Invalid_argument "CCList.range_by")
+  else if (if step > 0 then i>j else i<j) then
+    []
+  else
+    range i ((j-i)/step*step + i)  []
 
+(* note: the last test checks that no error occurs due to overflows. *)
 (*$T
   range_by ~step:1   0 0 = [0]
   range_by ~step:1   5 0 = []
+  range_by ~step:2   1 0 = []
   range_by ~step:2   0 4 = [0;2;4]
   range_by ~step:2   0 5 = [0;2;4]
+  range_by ~step:~-1 0 0 = [0]
   range_by ~step:~-1 0 5 = []
+  range_by ~step:~-2 0 1 = []
   range_by ~step:~-2 5 1 = [5;3;1]
   range_by ~step:~-2 5 0 = [5;3;1]
+  range_by ~step:max_int 0 2 = [0]
 *)
 
 let range i j =