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 5 package runtime 6 7 import "unsafe" 8 9 var inf = float64frombits(0x7FF0000000000000) 10 11 // isNaN reports whether f is an IEEE 754 ``not-a-number'' value. 12 func 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. 18 func isFinite(f float64) bool { 19 return !isNaN(f - f) 20 } 21 22 // isInf reports whether f is an infinity. 23 func 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 32 func 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. 39 func 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. 45 func 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. 51 func float64frombits(b uint64) float64 { 52 return *(*float64)(unsafe.Pointer(&b)) 53 } 54
