13e12c5d1SDavid du Colombier #include <math.h>
23e12c5d1SDavid du Colombier #include <stdlib.h>
33e12c5d1SDavid du Colombier double pow10(int);
43e12c5d1SDavid du Colombier #define NDIG 18
53e12c5d1SDavid du Colombier #define NFTOA (NDIG+4)
63e12c5d1SDavid du Colombier /*
73e12c5d1SDavid du Colombier * convert floating to ascii. ftoa returns an integer e such that
83e12c5d1SDavid du Colombier * f=g*10**e, with .1<=|g|<1 (e=0 when g==0) and puts an ascii
93e12c5d1SDavid du Colombier * representation of g in the buffer pointed to by bp. bp[0] will
103e12c5d1SDavid du Colombier * be '+' or '-', and bp[1] to bp[NFTOA-2]
113e12c5d1SDavid du Colombier * will be appropriate digits of g. bp[NFTOA-1] will be '\0'
123e12c5d1SDavid du Colombier */
ftoa(double f,char * bp)133e12c5d1SDavid du Colombier int ftoa(double f, char *bp){
143e12c5d1SDavid du Colombier int e, e1, e2, i;
153e12c5d1SDavid du Colombier double digit, g, p;
163e12c5d1SDavid du Colombier if(f>=0) *bp++='+';
173e12c5d1SDavid du Colombier else{
183e12c5d1SDavid du Colombier f=-f;
193e12c5d1SDavid du Colombier *bp++='-';
203e12c5d1SDavid du Colombier }
213e12c5d1SDavid du Colombier /* find e such that f==0 or 1<=f*pow10(e)<10, and set f=f*pow10(e) */
223e12c5d1SDavid du Colombier if(f==0.) e=1;
233e12c5d1SDavid du Colombier else{
243e12c5d1SDavid du Colombier frexp(f, &e);
253e12c5d1SDavid du Colombier e=-e*30103/100000;
263e12c5d1SDavid du Colombier /* split in 2 pieces to guard against overflow in extreme cases */
273e12c5d1SDavid du Colombier e1=e/2;
283e12c5d1SDavid du Colombier e2=e-e1;
293e12c5d1SDavid du Colombier p=f*pow10(e2);
30*22df390cSDavid du Colombier while(p*pow10(e1)<1.) e1++;
313e12c5d1SDavid du Colombier while((g=p*pow10(e1))>=10.) --e1;
323e12c5d1SDavid du Colombier e=e1+e2;
333e12c5d1SDavid du Colombier f=g;
343e12c5d1SDavid du Colombier }
353e12c5d1SDavid du Colombier for(i=0;i!=NDIG;i++){
363e12c5d1SDavid du Colombier f=modf(f, &digit)*10.;
373e12c5d1SDavid du Colombier *bp++=digit+'0';
383e12c5d1SDavid du Colombier }
393e12c5d1SDavid du Colombier *bp='\0';
403e12c5d1SDavid du Colombier return 1-e;
413e12c5d1SDavid du Colombier }
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