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Diffstat (limited to 'ext/bcmath/libbcmath/src/sqrt.c')
| -rw-r--r-- | ext/bcmath/libbcmath/src/sqrt.c | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/ext/bcmath/libbcmath/src/sqrt.c b/ext/bcmath/libbcmath/src/sqrt.c new file mode 100644 index 0000000000..34b95b8898 --- /dev/null +++ b/ext/bcmath/libbcmath/src/sqrt.c @@ -0,0 +1,131 @@ +/* sqrt.c: bcmath library file. */ +/* + Copyright (C) 1991, 1992, 1993, 1994, 1997 Free Software Foundation, Inc. + Copyright (C) 2000 Philip A. Nelson + + This library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2 of the License, or (at your option) any later version. + + This library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. (COPYING.LIB) + + You should have received a copy of the GNU Lesser General Public + License along with this library; if not, write to: + + The Free Software Foundation, Inc. + 59 Temple Place, Suite 330 + Boston, MA 02111-1307 USA. + + You may contact the author by: + e-mail: philnelson@acm.org + us-mail: Philip A. Nelson + Computer Science Department, 9062 + Western Washington University + Bellingham, WA 98226-9062 + +*************************************************************************/ + +#include <config.h> +#include <stdio.h> +#include <assert.h> +#include <stdlib.h> +#include <ctype.h> +#include <stdarg.h> +#include "bcmath.h" +#include "private.h" + +/* Take the square root NUM and return it in NUM with SCALE digits + after the decimal place. */ + +int +bc_sqrt (num, scale) + bc_num *num; + int scale; +{ + int rscale, cmp_res, done; + int cscale; + bc_num guess, guess1, point5, diff; + + /* Initial checks. */ + cmp_res = bc_compare (*num, _zero_); + if (cmp_res < 0) + return 0; /* error */ + else + { + if (cmp_res == 0) + { + bc_free_num (num); + *num = bc_copy_num (_zero_); + return 1; + } + } + cmp_res = bc_compare (*num, _one_); + if (cmp_res == 0) + { + bc_free_num (num); + *num = bc_copy_num (_one_); + return 1; + } + + /* Initialize the variables. */ + rscale = MAX (scale, (*num)->n_scale); + bc_init_num(&guess); + bc_init_num(&guess1); + bc_init_num(&diff); + point5 = bc_new_num (1,1); + point5->n_value[1] = 5; + + + /* Calculate the initial guess. */ + if (cmp_res < 0) + { + /* The number is between 0 and 1. Guess should start at 1. */ + guess = bc_copy_num (_one_); + cscale = (*num)->n_scale; + } + else + { + /* The number is greater than 1. Guess should start at 10^(exp/2). */ + bc_int2num (&guess,10); + + bc_int2num (&guess1,(*num)->n_len); + bc_multiply (guess1, point5, &guess1, 0); + guess1->n_scale = 0; + bc_raise (guess, guess1, &guess, 0); + bc_free_num (&guess1); + cscale = 3; + } + + /* Find the square root using Newton's algorithm. */ + done = FALSE; + while (!done) + { + bc_free_num (&guess1); + guess1 = bc_copy_num (guess); + bc_divide (*num, guess, &guess, cscale); + bc_add (guess, guess1, &guess, 0); + bc_multiply (guess, point5, &guess, cscale); + bc_sub (guess, guess1, &diff, cscale+1); + if (bc_is_near_zero (diff, cscale)) + { + if (cscale < rscale+1) + cscale = MIN (cscale*3, rscale+1); + else + done = TRUE; + } + } + + /* Assign the number and clean up. */ + bc_free_num (num); + bc_divide (guess,_one_,num,rscale); + bc_free_num (&guess); + bc_free_num (&guess1); + bc_free_num (&point5); + bc_free_num (&diff); + return 1; +} + |