jehanne/qa/kern/frexp.c

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#include <u.h>
#include <lib9.h>
#define DEEPS ".5*2^-1073"
#define DENEPS "-.5*2^-1073"
#define DEPINF "+Inf*2^0"
#define DENAN "NaN*2^0"
jmp_buf errj;
char *err;
int fail = 0;
void
catcher(void *u, char *s)
{
err = 0;
if(strncmp(s, "sys: fp:", 8) == 0){
err = s;
notejmp(u, errj, 0);
}
noted(NDFLT);
}
void
decomp(double d, int *exp, char *s)
{
double m;
m = frexp(d, exp);
fprint(2, "Expected decomposition: %s\n", s);
fprint(2, "Actual decomposition: %g*2^%d\n", m, *exp);
if(isNaN(d)){
if(*exp != 0 || !isNaN(m))
fail = 1;
return;
}
if(isInf(d, 1)){
if(*exp != 0 || !isInf(m, 1))
fail = 1;
return;
}
if(fabs(d - ldexp(m, *exp)) > 4e-16)
fail = 1;
}
void
main(void)
{
double eps, neps;
int exp;
err = 0;
notify(catcher);
setjmp(errj);
if(err){
print("FAIL: %s\n", err);
exits("FAIL");
}
eps = ldexp(1, -1074);
neps = ldexp(-1, -1074);
fprint(2, "Smallest Positive Double: %g\n", eps);
decomp(eps, &exp, DEEPS);
fprint(2, "Largest Negative Double: %g\n", neps);
decomp(neps, &exp, DENEPS);
fprint(2, "Positive infinity: %g\n", Inf(1));
decomp(Inf(1), &exp, DEPINF);
fprint(2, "NaN: %g\n", NaN());
decomp(NaN(), &exp, DENAN);
if(fail){
print("FAIL\n");
exits("FAIL");
}
print("PASS\n");
exits("PASS");
}