2008/8/12 Mikael Djurfeldt <[EMAIL PROTECTED]>:
> 2008/8/12 Neil Jerram <[EMAIL PROTECTED]>:
>> 2008/8/12 Bill Schottstaedt <[EMAIL PROTECTED]>:
>>> gcd is supposed to ignore factors of -1.
>>
>> According to? (I'm not suggesting that you're wrong. I'd just like
>> you to be precise about your references.)
>
> R5RS:
>
> 6.2.5 Numerical operations
>
> -- library procedure: gcd n1 ...,
> -- library procedure: lcm n1 ...,
> These procedures return the greatest common divisor or least common
> multiple of their arguments. The result is always non-negative.
Patch is attached, for review.
Neil
From 420a9ff5588852795bb3bbb99f878f0471e8fe58 Mon Sep 17 00:00:00 2001
From: Neil Jerram <[EMAIL PROTECTED]>
Date: Wed, 17 Sep 2008 21:46:40 +0100
Subject: [PATCH] Fix for incorrect (gcd -2) => -2; should give 2.
(reported by Bill Schottstaedt)
* libguile/numbers.c (scm_gcd): When only one arg given, use scm_abs
to ensure that result is non-negative.
* test-suite/tests/numbers.test ("gcd"): New test, (gcd -2).
---
NEWS | 1 +
libguile/numbers.c | 2 +-
test-suite/tests/numbers.test | 5 +++++
3 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/NEWS b/NEWS
index d5e4510..f4ca739 100644
--- a/NEWS
+++ b/NEWS
@@ -34,6 +34,7 @@ available: Guile is now always configured in "maintainer mode".
** Fix build issue on hppa2.0w-hp-hpux11.11 (`dirent64' and `readdir64_r')
** Fix misleading output from `(help rationalize)'
** Fix build failure on Debian hppa architecture (bad stack growth detection)
+** Fix `gcd' when called with a single, negative argument.
Changes in 1.8.5 (since 1.8.4)
diff --git a/libguile/numbers.c b/libguile/numbers.c
index 7a4d619..52dfb73 100644
--- a/libguile/numbers.c
+++ b/libguile/numbers.c
@@ -1022,7 +1022,7 @@ SCM
scm_gcd (SCM x, SCM y)
{
if (SCM_UNBNDP (y))
- return SCM_UNBNDP (x) ? SCM_INUM0 : x;
+ return SCM_UNBNDP (x) ? SCM_INUM0 : scm_abs (x);
if (SCM_I_INUMP (x))
{
diff --git a/test-suite/tests/numbers.test b/test-suite/tests/numbers.test
index 2c004f5..2dbc917 100644
--- a/test-suite/tests/numbers.test
+++ b/test-suite/tests/numbers.test
@@ -1059,6 +1059,11 @@
(expect-fail "documented?"
(documented? gcd))
+ (with-test-prefix "(n)"
+
+ (pass-if "n = -2"
+ (eqv? 2 (gcd -2))))
+
(with-test-prefix "(0 n)"
(pass-if "n = 0"
--
1.5.6.5
