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 //
   9 // Special cases are:
  10 //      Nextafter32(x, x)   = x
  11 //      Nextafter32(NaN, y) = NaN
  12 //      Nextafter32(x, NaN) = NaN
  13 func Nextafter32(x, y float32) (r float32) {
  14         switch {
  15         case IsNaN(float64(x)) || IsNaN(float64(y)): // special case
  16                 r = float32(NaN())
  17         case x == y:
  18                 r = x
  19         case x == 0:
  20                 r = float32(Copysign(float64(Float32frombits(1)), float64(y)))
  21         case (y > x) == (x > 0):
  22                 r = Float32frombits(Float32bits(x) + 1)
  23         default:
  24                 r = Float32frombits(Float32bits(x) - 1)
  25         }
  26         return
  27 }
  28
  29 // Nextafter returns the next representable float64 value after x towards y.
  30 //
  31 // Special cases are:
  32 //      Nextafter(x, x)   = x
  33 //      Nextafter(NaN, y) = NaN
  34 //      Nextafter(x, NaN) = NaN
  35 func Nextafter(x, y float64) (r float64) {
  36         switch {
  37         case IsNaN(x) || IsNaN(y): // special case
  38                 r = NaN()
  39         case x == y:
  40                 r = x
  41         case x == 0:
  42                 r = Copysign(Float64frombits(1), y)
  43         case (y > x) == (x > 0):
  44                 r = Float64frombits(Float64bits(x) + 1)
  45         default:
  46                 r = Float64frombits(Float64bits(x) - 1)
  47         }
  48         return
  49 }