libgo/go/runtime/float.go

   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 }