golang float 代码
文件路径：/src/runtime/float.go
/ Copyright 2017 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 runtime
import "unsafe"
var inf = float64frombits(0x7FF0000000000000)
/ isNaN reports whether f is an IEEE 754 “not-a-number” value.
func isNaN(f float64) (is bool) {
/ IEEE 754 says that only NaNs satisfy f != f.
return f != f
}
/ isFinite reports whether f is neither NaN nor an infinity.
func isFinite(f float64) bool {
return !isNaN(f - f)
}
/ isInf reports whether f is an infinity.
func isInf(f float64) bool {
return !isNaN(f) && !isFinite(f)
}
/ Abs returns the absolute value of x.
/
/ Special cases are:
/
/ Abs(±Inf) = +Inf
/ Abs(NaN) = NaN
func abs(x float64) float64 {
const sign = 1 << 63
return float64frombits(float64bits(x) &^ sign)
}
/ copysign returns a value with the magnitude
/ of x and the sign of y.
func copysign(x, y float64) float64 {
const sign = 1 << 63
return float64frombits(float64bits(x)&^sign | float64bits(y)&sign)
}
/ Float64bits returns the IEEE 754 binary representation of f.
func float64bits(f float64) uint64 {
return *(*uint64)(unsafe.Pointer(&f))
}
/ Float64frombits returns the floating point number corresponding
/ the IEEE 754 binary representation b.
func float64frombits(b uint64) float64 {
return *(*float64)(unsafe.Pointer(&b))
}