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core: Avoid Floating point exception dividing negative numbers. 

This fixes

    kaem --verbose --strict
    bin/mes-m2 -c '(display (modulo -1 -1))'

* src/math.c (modulo): Use unsigned division.
This commit is contained in:
Jan (janneke) Nieuwenhuizen 2021-01-01 09:04:39 +01:00
parent aac33c44b7
commit 6a25b8d3aa
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1 changed files with 20 additions and 10 deletions
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src/math.c
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@ -1,6 +1,6 @@
/* -*-comment-start: "//";comment-end:""-*- /* -*-comment-start: "//";comment-end:""-*-
* GNU Mes --- Maxwell Equations of Software * GNU Mes --- Maxwell Equations of Software
* Copyright © 2016,2017,2018,2019,2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org> * Copyright © 2016,2017,2018,2019,2020,2021 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
* Copyright © 2021 W. J. van der Laan <laanwj@protonmail.com> * Copyright © 2021 W. J. van der Laan <laanwj@protonmail.com>
* *
* This file is part of GNU Mes. * This file is part of GNU Mes.
@ -190,16 +190,26 @@ modulo (struct scm *a, struct scm *b)
{ {
assert_number ("modulo", a); assert_number ("modulo", a);
assert_number ("modulo", b); assert_number ("modulo", b);
long x = a->value; long n = a->value;
long y = b->value; long v = b->value;
if (y == 0) if (v == 0)
error (cstring_to_symbol ("divide-by-zero"), a); error (cstring_to_symbol ("divide-by-zero"), a);
while (x < 0) int sign_p = 0;
x = x + y; size_t w = v;
if (x != 0) if (v < 0)
x = x % y; {
sign_p = 1;
return make_number (x); w = -v;
}
while (n < 0)
n = n + w;
size_t u = n;
if (u != 0)
u = u % w;
n = u;
if (sign_p)
n = -n;
return make_number (n);
} }
struct scm * struct scm *