libgo/go/math/nextafter.go

   1 // Copyright 2010 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 math
   6
   7 // Nextafter32 returns the next representable float32 value after x towards y.
   8 // Special cases:
   9 //      Nextafter32(x, x)   = x
  10 //      Nextafter32(NaN, y) = NaN
  11 //      Nextafter32(x, NaN) = NaN
  12 func Nextafter32(x, y float32) (r float32) {
  13         switch {
  14         case IsNaN(float64(x)) || IsNaN(float64(y)): // special case
  15                 r = float32(NaN())
  16         case x == y:
  17                 r = x
  18         case x == 0:
  19                 r = float32(Copysign(float64(Float32frombits(1)), float64(y)))
  20         case (y > x) == (x > 0):
  21                 r = Float32frombits(Float32bits(x) + 1)
  22         default:
  23                 r = Float32frombits(Float32bits(x) - 1)
  24         }
  25         return
  26 }
  27
  28 // Nextafter returns the next representable float64 value after x towards y.
  29 // Special cases:
  30 //      Nextafter64(x, x)   = x
  31 //      Nextafter64(NaN, y) = NaN
  32 //      Nextafter64(x, NaN) = NaN
  33 func Nextafter(x, y float64) (r float64) {
  34         switch {
  35         case IsNaN(x) || IsNaN(y): // special case
  36                 r = NaN()
  37         case x == y:
  38                 r = x
  39         case x == 0:
  40                 r = Copysign(Float64frombits(1), y)
  41         case (y > x) == (x > 0):
  42                 r = Float64frombits(Float64bits(x) + 1)
  43         default:
  44                 r = Float64frombits(Float64bits(x) - 1)
  45         }
  46         return
  47 }