scm_difference gremlin

scm_difference gremlin

[Kevin Ryde]

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A small bug in scm_difference,

	* numbers.c (scm_difference): In inum - bignum, handle negative inum.

	* tests/numbers.test (-): Add test for negative inum subtract bignum.


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--- numbers.c.~1.181.~	2003-05-04 09:09:49.000000000 +1000
+++ numbers.c	2003-05-04 09:25:07.000000000 +1000
@@ -3060,7 +3060,14 @@
           int sgn_y = mpz_sgn (SCM_I_BIG_MPZ (y));
           SCM result = scm_i_mkbig ();
 
-          mpz_ui_sub (SCM_I_BIG_MPZ (result), xx, SCM_I_BIG_MPZ (y));
+          if (xx >= 0)
+            mpz_ui_sub (SCM_I_BIG_MPZ (result), xx, SCM_I_BIG_MPZ (y));
+          else
+            {
+              /* x - y == -(y + -x) */
+              mpz_add_ui (SCM_I_BIG_MPZ (result), SCM_I_BIG_MPZ (y), -xx);
+              mpz_neg (SCM_I_BIG_MPZ (result), SCM_I_BIG_MPZ (result));
+            }
           scm_remember_upto_here_1 (y);
 
           if ((xx < 0 && (sgn_y > 0)) || ((xx > 0) && sgn_y < 0))

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--- numbers.test.~1.17.~	2003-05-04 09:11:34.000000000 +1000
+++ numbers.test	2003-05-04 09:27:55.000000000 +1000
@@ -1,5 +1,5 @@
 ;;;; numbers.test --- tests guile's numbers     -*- scheme -*-
-;;;; Copyright (C) 2000, 2001 Free Software Foundation, Inc.
+;;;; Copyright (C) 2000, 2001, 2003 Free Software Foundation, Inc.
 ;;;;
 ;;;; This library is free software; you can redistribute it and/or
 ;;;; modify it under the terms of the GNU Lesser General Public
@@ -1609,6 +1609,12 @@
 ;;; -
 ;;;
 
+(with-test-prefix "-"
+
+  (pass-if "-inum - +bignum"
+    (= #x-100000000000000000000000000000001
+       (- -1 #x100000000000000000000000000000000))))
+
 ;;;
 ;;; *
 ;;;

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Re: scm_difference gremlin

[Marius Vollmer]

Kevin Ryde <user42@zip.com.au> writes:

> A small bug in scm_difference,

Excellent, please apply (when Rob doesn't object).

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Re: scm_difference gremlin

[Rob Browning]

Marius Vollmer <mvo@zagadka.de> writes:

>> A small bug in scm_difference,
>
> Excellent, please apply (when Rob doesn't object).

No objection here.

Thanks

-- 
Rob Browning
rlb @defaultvalue.org, @linuxdevel.com, and @debian.org
Previously @cs.utexas.edu
GPG starting 2002-11-03 = 14DD 432F AE39 534D B592  F9A0 25C8 D377 8C7E 73A4


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