gcc/libgo/go/math/mod.go
Ian Lance Taylor 9a0e3259f4 libgo: Update to weekly.2011-12-14.
From-SVN: r183118
2012-01-12 01:31:45 +00:00

56 lines
1.1 KiB
Go

// Copyright 2009-2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package math
/*
Floating-point mod function.
*/
// Mod returns the floating-point remainder of x/y.
// The magnitude of the result is less than y and its
// sign agrees with that of x.
//
// Special cases are:
// Mod(±Inf, y) = NaN
// Mod(NaN, y) = NaN
// Mod(x, 0) = NaN
// Mod(x, ±Inf) = x
// Mod(x, NaN) = NaN
func libc_fmod(float64, float64) float64 __asm__("fmod")
func Mod(x, y float64) float64 {
return libc_fmod(x, y)
}
func mod(x, y float64) float64 {
// TODO(rsc): Remove manual inlining of IsNaN, IsInf
// when compiler does it for us.
if y == 0 || x > MaxFloat64 || x < -MaxFloat64 || x != x || y != y { // y == 0 || IsInf(x, 0) || IsNaN(x) || IsNan(y)
return NaN()
}
if y < 0 {
y = -y
}
yfr, yexp := Frexp(y)
sign := false
r := x
if x < 0 {
r = -x
sign = true
}
for r >= y {
rfr, rexp := Frexp(r)
if rfr < yfr {
rexp = rexp - 1
}
r = r - Ldexp(y, rexp-yexp)
}
if sign {
r = -r
}
return r
}