File:  [gforth] / gforth / engine / ecvt.c
Revision 1.10: download - view: text, annotated - select for diffs
Mon Dec 31 18:40:25 2007 UTC (13 years, 7 months ago) by anton
Branches: MAIN
CVS tags: v0-7-0, HEAD
updated copyright notices for GPL v3

    1: /* cheap ecvt replacement
    2: 
    3:   Copyright (C) 1998,2000,2007 Free Software Foundation, Inc.
    4: 
    5:   This file is part of Gforth.
    6: 
    7:   Gforth is free software; you can redistribute it and/or
    8:   modify it under the terms of the GNU General Public License
    9:   as published by the Free Software Foundation, either version 3
   10:   of the License, or (at your option) any later version.
   11: 
   12:   This program is distributed in the hope that it will be useful,
   13:   but WITHOUT ANY WARRANTY; without even the implied warranty of
   14:   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   15:   GNU General Public License for more details.
   16: 
   17:   You should have received a copy of the GNU General Public License
   18:   along with this program; if not, see http://www.gnu.org/licenses/.
   19: */
   20: 
   21: #include <stdio.h>
   22: #include "config.h"
   23: #include <math.h>
   24: extern double floor(double);
   25: extern double pow10(double);
   26: 
   27: #define MAXCONV 0x40
   28: char scratch[MAXCONV];
   29: 
   30: char* ecvt(double x, int len, int* exp, int* sign)
   31: {
   32:    int i, j;
   33:    double z;
   34:    
   35:    if (isnan(x)) {
   36:      *sign=0;
   37:      *exp=0;
   38:      return "nan";
   39:    }
   40:    if (isinf(x)) {
   41:      *sign=0; /* this mimics the glibc ecvt */
   42:      *exp=0;
   43:      if (x<0)
   44:        return "-inf";
   45:      else
   46:        return "inf";
   47:    }
   48:        
   49:    if(len > (MAXCONV-1)) len = MAXCONV-1;
   50:    
   51:    if(x<0)
   52:      {
   53: 	*sign = 1;
   54: 	x = -x;
   55:      }
   56:    else
   57:      {
   58: 	*sign = 0;
   59:      }
   60: 
   61:    if(x==0)
   62: 	*exp=-1;
   63:    else
   64:      *exp=(int)floor(log10(x));
   65:    x = x / pow10((double)*exp);
   66:    
   67:    *exp += 1;
   68:    
   69:    for(i=0; i < len; i++)
   70:      {
   71: 	z=floor(x);
   72: 	if(z<0) z = 0;
   73: 	scratch[i]='0'+(char)((int)z);
   74: 	x = (x-z)*10;
   75:      }
   76:    
   77:    if((x >= 5) && i)
   78:      {
   79: 	for(j=i-1; j>=0; j--)
   80: 	  {
   81: 	     if(scratch[j]!='9')
   82: 	       {
   83: 		  scratch[j]+=1; break;
   84: 	       }
   85: 	     else
   86: 	       {
   87: 		  scratch[j]='0';
   88: 	       }
   89: 	  }
   90: 	if(j<0)
   91: 	  {
   92: 	     scratch[0]='1';
   93: 	     *exp += 1;
   94: 	  }
   95:      }
   96:    
   97:    scratch[i]='\0';
   98:    
   99:    return scratch;
  100: }
  101: 
  102: #ifdef TEST
  103: int main(int argc, char ** argv)
  104: {
  105:    int a, b;
  106:    char * conv=ecvt(9e0,20,&a,&b);
  107:    
  108:    printf("ecvt Test: %f -> %s, %d, %d\n",9e0,conv,a,b);
  109: }
  110: #endif
  111: 

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