shithub: npe

ref: fd731d3c833d9241fdff618b6c949453fb5c0f31
dir: /math.c/

#include <math.h>

/* some of these were taken from musl */

#define ln2o1 1.4426950408889634073599
#define dbleps 2.2204460492503131e-16
#define huge 1.79769313486231e+308

static double toint = 1.0/dbleps;

double
round(double x)
{
	union {double f; u64int i;} u = {x};
	int e = u.i >> 52 & 0x7ff;
	double y;

	if(e >= 0x3ff+52)
		return x;
	if(u.i >> 63)
		x = -x;
	if(e < 0x3ff-1)
		return 0*u.f;
	y = x + toint - toint - x;
	if(y > 0.5)
		y = y + x - 1;
	else if(y <= -0.5)
		y = y + x + 1;
	else
		y = y + x;
	if(u.i >> 63)
		y = -y;

	return y;
}

double
log2(double x)
{
	if(x == 0)
		return -huge;
	if(x < 0 || isNaN(x))
		return NaN();

	return log(x)*ln2o1;
}

double
trunc(double x)
{
	union {double f; u64int i;} u = {x};
	int e = (int)(u.i >> 52 & 0x7ff) - 0x3ff + 12;
	u64int m;

	if(e >= 52 + 12)
		return x;
	if(e < 12)
		e = 1;
	m = -1ULL >> e;
	if((u.i & m) == 0)
		return x;
	u.i &= ~m;

	return u.f;
}

double
exp2(double x)
{
	return exp(x/ln2o1);
}