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1.1 misho 1: /* raise.c: bcmath library file. */ 2: /* 3: Copyright (C) 1991, 1992, 1993, 1994, 1997 Free Software Foundation, Inc. 4: Copyright (C) 2000 Philip A. Nelson 5: 6: This library is free software; you can redistribute it and/or 7: modify it under the terms of the GNU Lesser General Public 8: License as published by the Free Software Foundation; either 9: version 2 of the License, or (at your option) any later version. 10: 11: This library is distributed in the hope that it will be useful, 12: but WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: Lesser General Public License for more details. (COPYING.LIB) 15: 16: You should have received a copy of the GNU Lesser General Public 17: License along with this library; if not, write to: 18: 19: The Free Software Foundation, Inc. 20: 59 Temple Place, Suite 330 21: Boston, MA 02111-1307 USA. 22: 23: You may contact the author by: 24: e-mail: philnelson@acm.org 25: us-mail: Philip A. Nelson 26: Computer Science Department, 9062 27: Western Washington University 28: Bellingham, WA 98226-9062 29: 30: *************************************************************************/ 31: 32: #include <config.h> 33: #include <stdio.h> 34: #include <assert.h> 35: #include <stdlib.h> 36: #include <ctype.h> 37: #include <stdarg.h> 38: #include "bcmath.h" 39: #include "private.h" 40: 41: 42: /* Raise NUM1 to the NUM2 power. The result is placed in RESULT. 43: Maximum exponent is LONG_MAX. If a NUM2 is not an integer, 44: only the integer part is used. */ 45: 46: void 47: bc_raise (bc_num num1, bc_num num2, bc_num *result, int scale TSRMLS_DC) 48: { 49: bc_num temp, power; 50: long exponent; 51: int rscale; 52: int pwrscale; 53: int calcscale; 54: char neg; 55: 56: /* Check the exponent for scale digits and convert to a long. */ 57: if (num2->n_scale != 0) 58: bc_rt_warn ("non-zero scale in exponent"); 59: exponent = bc_num2long (num2); 60: if (exponent == 0 && (num2->n_len > 1 || num2->n_value[0] != 0)) 61: bc_rt_error ("exponent too large in raise"); 62: 63: /* Special case if exponent is a zero. */ 64: if (exponent == 0) 65: { 66: bc_free_num (result); 67: *result = bc_copy_num (BCG(_one_)); 68: return; 69: } 70: 71: /* Other initializations. */ 72: if (exponent < 0) 73: { 74: neg = TRUE; 75: exponent = -exponent; 76: rscale = scale; 77: } 78: else 79: { 80: neg = FALSE; 81: rscale = MIN (num1->n_scale*exponent, MAX(scale, num1->n_scale)); 82: } 83: 84: /* Set initial value of temp. */ 85: power = bc_copy_num (num1); 86: pwrscale = num1->n_scale; 87: while ((exponent & 1) == 0) 88: { 89: pwrscale = 2*pwrscale; 90: bc_multiply (power, power, &power, pwrscale TSRMLS_CC); 91: exponent = exponent >> 1; 92: } 93: temp = bc_copy_num (power); 94: calcscale = pwrscale; 95: exponent = exponent >> 1; 96: 97: /* Do the calculation. */ 98: while (exponent > 0) 99: { 100: pwrscale = 2*pwrscale; 101: bc_multiply (power, power, &power, pwrscale TSRMLS_CC); 102: if ((exponent & 1) == 1) { 103: calcscale = pwrscale + calcscale; 104: bc_multiply (temp, power, &temp, calcscale TSRMLS_CC); 105: } 106: exponent = exponent >> 1; 107: } 108: 109: /* Assign the value. */ 110: if (neg) 111: { 112: bc_divide (BCG(_one_), temp, result, rscale TSRMLS_CC); 113: bc_free_num (&temp); 114: } 115: else 116: { 117: bc_free_num (result); 118: *result = temp; 119: if ((*result)->n_scale > rscale) 120: (*result)->n_scale = rscale; 121: } 122: bc_free_num (&power); 123: } 124: