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e56ed6e1ab
Re-formats the BCmath extension to have consistent formatting. Mostly, it adds the spaces in calculations to have them more readable. Also: - removes unused headers - removes few variables which are used only once in the code Co-authored-by: George Peter Banyard <girgias@php.net>
116 lines
3.2 KiB
C
116 lines
3.2 KiB
C
/* sqrt.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 <stdbool.h>
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#include <stddef.h>
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/* Take the square root NUM and return it in NUM with SCALE digits
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after the decimal place. */
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bool bc_sqrt(bc_num *num, size_t scale)
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{
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/* Initial checks. */
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int cmp_res = bc_compare(*num, BCG(_zero_));
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if (cmp_res < 0) {
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return false; /* error */
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} else {
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if (cmp_res == 0) {
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bc_free_num (num);
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*num = bc_copy_num(BCG(_zero_));
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return true;
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}
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}
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cmp_res = bc_compare(*num, BCG(_one_));
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if (cmp_res == 0) {
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bc_free_num (num);
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*num = bc_copy_num(BCG(_one_));
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return true;
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}
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/* Initialize the variables. */
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size_t rscale;
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size_t cscale;
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bc_num guess, guess1, point5, diff;
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rscale = MAX (scale, (*num)->n_scale);
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bc_init_num(&guess1);
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bc_init_num(&diff);
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point5 = bc_new_num (1, 1);
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point5->n_value[1] = 5;
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/* Calculate the initial guess. */
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if (cmp_res < 0) {
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/* The number is between 0 and 1. Guess should start at 1. */
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guess = bc_copy_num(BCG(_one_));
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cscale = (*num)->n_scale;
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} else {
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/* The number is greater than 1. Guess should start at 10^(exp/2). */
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bc_init_num(&guess);
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bc_int2num(&guess, 10);
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bc_int2num(&guess1, (*num)->n_len);
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bc_multiply(guess1, point5, &guess1, 0);
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guess1->n_scale = 0;
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bc_raise_bc_exponent(guess, guess1, &guess, 0);
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bc_free_num (&guess1);
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cscale = 3;
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}
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/* Find the square root using Newton's algorithm. */
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bool done = false;
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while (!done) {
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bc_free_num (&guess1);
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guess1 = bc_copy_num(guess);
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bc_divide(*num, guess, &guess, cscale);
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bc_add(guess, guess1, &guess, 0);
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bc_multiply(guess, point5, &guess, cscale);
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bc_sub(guess, guess1, &diff, cscale + 1);
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if (bc_is_near_zero(diff, cscale)) {
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if (cscale < rscale + 1) {
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cscale = MIN (cscale * 3, rscale + 1);
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} else {
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done = true;
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}
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}
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}
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/* Assign the number and clean up. */
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bc_free_num (num);
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bc_divide(guess, BCG(_one_), num, rscale);
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bc_free_num (&guess);
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bc_free_num (&guess1);
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bc_free_num (&point5);
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bc_free_num (&diff);
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return true;
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}
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