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125 lines
3.4 KiB
C
125 lines
3.4 KiB
C
/* raise.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. (COPYING.LIB)
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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 <config.h>
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#include <stdio.h>
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#include <assert.h>
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#include <stdlib.h>
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#include <ctype.h>
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#include <stdarg.h>
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#include "bcmath.h"
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#include "private.h"
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/* Raise NUM1 to the NUM2 power. The result is placed in RESULT.
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Maximum exponent is LONG_MAX. If a NUM2 is not an integer,
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only the integer part is used. */
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void
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bc_raise (bc_num num1, bc_num num2, bc_num *result, int scale TSRMLS_DC)
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{
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bc_num temp, power;
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long exponent;
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int rscale;
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int pwrscale;
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int calcscale;
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char neg;
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/* Check the exponent for scale digits and convert to a long. */
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if (num2->n_scale != 0)
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bc_rt_warn ("non-zero scale in exponent");
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exponent = bc_num2long (num2);
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if (exponent == 0 && (num2->n_len > 1 || num2->n_value[0] != 0))
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bc_rt_error ("exponent too large in raise");
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/* Special case if exponent is a zero. */
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if (exponent == 0)
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{
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bc_free_num (result);
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*result = bc_copy_num (BCG(_one_));
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return;
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}
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/* Other initializations. */
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if (exponent < 0)
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{
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neg = TRUE;
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exponent = -exponent;
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rscale = scale;
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}
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else
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{
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neg = FALSE;
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rscale = MIN (num1->n_scale*exponent, MAX(scale, num1->n_scale));
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}
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/* Set initial value of temp. */
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power = bc_copy_num (num1);
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pwrscale = num1->n_scale;
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while ((exponent & 1) == 0)
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{
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pwrscale = 2*pwrscale;
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bc_multiply (power, power, &power, pwrscale TSRMLS_CC);
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exponent = exponent >> 1;
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}
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temp = bc_copy_num (power);
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calcscale = pwrscale;
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exponent = exponent >> 1;
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/* Do the calculation. */
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while (exponent > 0)
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{
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pwrscale = 2*pwrscale;
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bc_multiply (power, power, &power, pwrscale TSRMLS_CC);
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if ((exponent & 1) == 1) {
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calcscale = pwrscale + calcscale;
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bc_multiply (temp, power, &temp, calcscale TSRMLS_CC);
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}
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exponent = exponent >> 1;
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}
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/* Assign the value. */
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if (neg)
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{
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bc_divide (BCG(_one_), temp, result, rscale TSRMLS_CC);
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bc_free_num (&temp);
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}
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else
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{
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bc_free_num (result);
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*result = temp;
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if ((*result)->n_scale > rscale)
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(*result)->n_scale = rscale;
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}
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bc_free_num (&power);
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}
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