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be4b10e95e
In the original specification, the scale of bc_num was directly changed and compared. This becomes a problem when objects are supported, so we will modify it to compare without changing bc_num.
74 lines
2.3 KiB
C
74 lines
2.3 KiB
C
/* sub.c: bcmath library file. */
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/*
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Copyright (C) 1991, 1992, 1993, 1994, 1997 Free Software Foundation, Inc.
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Copyright (C) 2000 Philip A. Nelson
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details. (LICENSE)
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to:
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The Free Software Foundation, Inc.
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59 Temple Place, Suite 330
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Boston, MA 02111-1307 USA.
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You may contact the author by:
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e-mail: philnelson@acm.org
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us-mail: Philip A. Nelson
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Computer Science Department, 9062
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Western Washington University
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Bellingham, WA 98226-9062
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*************************************************************************/
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#include "bcmath.h"
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#include "private.h"
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#include <stddef.h>
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#include <stdbool.h>
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#include <string.h>
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/* Here is the full subtract routine that takes care of negative numbers.
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N2 is subtracted from N1 and the result placed in RESULT. SCALE_MIN
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is the minimum scale for the result. */
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bc_num bc_sub(bc_num n1, bc_num n2, size_t scale_min)
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{
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bc_num diff = NULL;
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if (n1->n_sign != n2->n_sign) {
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diff = _bc_do_add(n1, n2);
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diff->n_sign = n1->n_sign;
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} else {
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/* subtraction must be done. */
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/* Compare magnitudes. */
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switch (_bc_do_compare(n1, n2, scale_min, false)) {
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case BCMATH_RIGHT_GREATER:
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/* n1 is less than n2, subtract n1 from n2. */
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diff = _bc_do_sub(n2, n1);
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diff->n_sign = (n2->n_sign == PLUS ? MINUS : PLUS);
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break;
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case BCMATH_EQUAL: {
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/* They are equal! return zero! */
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size_t res_scale = MAX (scale_min, MAX(n1->n_scale, n2->n_scale));
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diff = bc_new_num (1, res_scale);
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break;
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}
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case BCMATH_LEFT_GREATER:
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/* n2 is less than n1, subtract n2 from n1. */
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diff = _bc_do_sub(n1, n2);
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diff->n_sign = n1->n_sign;
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break;
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}
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}
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return diff;
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}
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