femtolisp/llt/dblprint.c

122 lines
2.9 KiB
C

#include <math.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include "dtypes.h"
#include "ieee754.h"
int double_exponent(double d)
{
union ieee754_double dl;
dl.d = d;
return dl.ieee.exponent - IEEE754_DOUBLE_BIAS;
}
double double_mantissa(double d)
{
union ieee754_double dl;
dl.d = d;
dl.ieee.exponent = IEEE754_DOUBLE_BIAS;
dl.ieee.negative = 0;
return dl.d;
}
int float_exponent(float f)
{
union ieee754_float fl;
fl.f = f;
return fl.ieee.exponent - IEEE754_FLOAT_BIAS;
}
float float_mantissa(float f)
{
union ieee754_float fl;
fl.f = f;
fl.ieee.exponent = IEEE754_FLOAT_BIAS;
fl.ieee.negative = 0;
return fl.f;
}
void snprint_real(char *s, size_t cnt, double r,
int width, // printf field width, or 0
int dec, // # decimal digits desired, recommend 16
// # of zeros in .00...0x before using scientific notation
// recommend 3-4 or so
int max_digs_rt,
// # of digits left of decimal before scientific notation
// recommend 10
int max_digs_lf)
{
int mag;
double fpart, temp;
char format[8];
char num_format[3];
int sz, keepz=0;
s[0] = '\0';
if (width == -1) {
width = 0;
keepz=1;
}
if (isnan(r)) {
if (sign_bit(r))
strncpy(s, "-nan", cnt);
else
strncpy(s, "nan", cnt);
return;
}
if (r == 0) {
strncpy(s, "0", cnt);
return;
}
num_format[0] = 'l';
num_format[2] = '\0';
mag = double_exponent(r);
mag = (int)(((double)mag)/LOG2_10 + 0.5);
if (r == 0)
mag = 0;
if ((mag > max_digs_lf-1) || (mag < -max_digs_rt)) {
num_format[1] = 'e';
temp = r/pow(10, mag); /* see if number will have a decimal */
fpart = temp - floor(temp); /* when written in scientific notation */
}
else {
num_format[1] = 'f';
fpart = r - floor(r);
}
if (fpart == 0)
dec = 0;
if (width == 0) {
snprintf(format, 8, "%%.%d%s", dec, num_format);
}
else {
snprintf(format, 8, "%%%d.%d%s", width, dec, num_format);
}
sz = snprintf(s, cnt, format, r);
/* trim trailing zeros from fractions. not when using scientific
notation, since we might have e.g. 1.2000e+100. also not when we
need a specific output width */
if (width == 0 && !keepz) {
if (sz > 2 && fpart && num_format[1]!='e') {
while (s[sz-1] == '0') {
s[sz-1]='\0';
sz--;
}
// don't need trailing .
if (s[sz-1] == '.') {
s[sz-1] = '\0';
sz--;
}
}
}
// TODO. currently 1.1e20 prints as 1.1000000000000000e+20; be able to
// get rid of all those zeros.
}