1// Copyright 2017 The Go Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style 3// license that can be found in the LICENSE file. 4 5package runtime 6 7import "unsafe" 8 9var inf = float64frombits(0x7FF0000000000000) 10 11// isNaN reports whether f is an IEEE 754 ``not-a-number'' value. 12func isNaN(f float64) (is bool) { 13 // IEEE 754 says that only NaNs satisfy f != f. 14 return f != f 15} 16 17// isFinite reports whether f is neither NaN nor an infinity. 18func isFinite(f float64) bool { 19 return !isNaN(f - f) 20} 21 22// isInf reports whether f is an infinity. 23func isInf(f float64) bool { 24 return !isNaN(f) && !isFinite(f) 25} 26 27// Abs returns the absolute value of x. 28// 29// Special cases are: 30// Abs(±Inf) = +Inf 31// Abs(NaN) = NaN 32func abs(x float64) float64 { 33 const sign = 1 << 63 34 return float64frombits(float64bits(x) &^ sign) 35} 36 37// copysign returns a value with the magnitude 38// of x and the sign of y. 39func copysign(x, y float64) float64 { 40 const sign = 1 << 63 41 return float64frombits(float64bits(x)&^sign | float64bits(y)&sign) 42} 43 44// Float64bits returns the IEEE 754 binary representation of f. 45func float64bits(f float64) uint64 { 46 return *(*uint64)(unsafe.Pointer(&f)) 47} 48 49// Float64frombits returns the floating point number corresponding 50// the IEEE 754 binary representation b. 51func float64frombits(b uint64) float64 { 52 return *(*float64)(unsafe.Pointer(&b)) 53} 54