libgo/go/math/dim.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 // Dim returns the maximum of x-y or 0.
   8 //
   9 // Special cases are:
  10 //      Dim(+Inf, +Inf) = NaN
  11 //      Dim(-Inf, -Inf) = NaN
  12 //      Dim(x, NaN) = Dim(NaN, x) = NaN
  13 func Dim(x, y float64) float64 {
  14         return dim(x, y)
  15 }
  16
  17 func dim(x, y float64) float64 {
  18         return max(x-y, 0)
  19 }
  20
  21 // Max returns the larger of x or y.
  22 //
  23 // Special cases are:
  24 //      Max(x, +Inf) = Max(+Inf, x) = +Inf
  25 //      Max(x, NaN) = Max(NaN, x) = NaN
  26 //      Max(+0, ±0) = Max(±0, +0) = +0
  27 //      Max(-0, -0) = -0
  28 func Max(x, y float64) float64 {
  29         return max(x, y)
  30 }
  31
  32 func max(x, y float64) float64 {
  33         // special cases
  34         switch {
  35         case IsInf(x, 1) || IsInf(y, 1):
  36                 return Inf(1)
  37         case IsNaN(x) || IsNaN(y):
  38                 return NaN()
  39         case x == 0 && x == y:
  40                 if Signbit(x) {
  41                         return y
  42                 }
  43                 return x
  44         }
  45         if x > y {
  46                 return x
  47         }
  48         return y
  49 }
  50
  51 // Min returns the smaller of x or y.
  52 //
  53 // Special cases are:
  54 //      Min(x, -Inf) = Min(-Inf, x) = -Inf
  55 //      Min(x, NaN) = Min(NaN, x) = NaN
  56 //      Min(-0, ±0) = Min(±0, -0) = -0
  57 func Min(x, y float64) float64 {
  58         return min(x, y)
  59 }
  60
  61 func min(x, y float64) float64 {
  62         // special cases
  63         switch {
  64         case IsInf(x, -1) || IsInf(y, -1):
  65                 return Inf(-1)
  66         case IsNaN(x) || IsNaN(y):
  67                 return NaN()
  68         case x == 0 && x == y:
  69                 if Signbit(x) {
  70                         return x
  71                 }
  72                 return y
  73         }
  74         if x < y {
  75                 return x
  76         }
  77         return y
  78 }