github.com/xushiwei/go@v0.0.0-20130601165731-2b9d83f45bc9/src/pkg/math/nextafter.go (about)

     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  // Nextafter returns the next representable value after x towards y.
     8  // If x == y, then x is returned.
     9  //
    10  // Special cases are:
    11  //      Nextafter(NaN, y) = NaN
    12  //      Nextafter(x, NaN) = NaN
    13  func Nextafter(x, y float64) (r float64) {
    14  	switch {
    15  	case IsNaN(x) || IsNaN(y): // special case
    16  		r = NaN()
    17  	case x == y:
    18  		r = x
    19  	case x == 0:
    20  		r = Copysign(Float64frombits(1), y)
    21  	case (y > x) == (x > 0):
    22  		r = Float64frombits(Float64bits(x) + 1)
    23  	default:
    24  		r = Float64frombits(Float64bits(x) - 1)
    25  	}
    26  	return
    27  }