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         // The special cases result in NaN after the subtraction:
  15         //      +Inf - +Inf = NaN
  16         //      -Inf - -Inf = NaN
  17         //       NaN - y    = NaN
  18         //         x - NaN  = NaN
  19         v := x - y
  20         if v <= 0 {
  21                 // v is negative or 0
  22                 return 0
  23         }
  24         // v is positive or NaN
  25         return v
  26 }
  27
  28 // Max returns the larger of x or y.
  29 //
  30 // Special cases are:
  31 //      Max(x, +Inf) = Max(+Inf, x) = +Inf
  32 //      Max(x, NaN) = Max(NaN, x) = NaN
  33 //      Max(+0, ±0) = Max(±0, +0) = +0
  34 //      Max(-0, -0) = -0
  35 func Max(x, y float64) float64 {
  36         return max(x, y)
  37 }
  38
  39 func max(x, y float64) float64 {
  40         // special cases
  41         switch {
  42         case IsInf(x, 1) || IsInf(y, 1):
  43                 return Inf(1)
  44         case IsNaN(x) || IsNaN(y):
  45                 return NaN()
  46         case x == 0 && x == y:
  47                 if Signbit(x) {
  48                         return y
  49                 }
  50                 return x
  51         }
  52         if x > y {
  53                 return x
  54         }
  55         return y
  56 }
  57
  58 // Min returns the smaller of x or y.
  59 //
  60 // Special cases are:
  61 //      Min(x, -Inf) = Min(-Inf, x) = -Inf
  62 //      Min(x, NaN) = Min(NaN, x) = NaN
  63 //      Min(-0, ±0) = Min(±0, -0) = -0
  64 func Min(x, y float64) float64 {
  65         return min(x, y)
  66 }
  67
  68 func min(x, y float64) float64 {
  69         // special cases
  70         switch {
  71         case IsInf(x, -1) || IsInf(y, -1):
  72                 return Inf(-1)
  73         case IsNaN(x) || IsNaN(y):
  74                 return NaN()
  75         case x == 0 && x == y:
  76                 if Signbit(x) {
  77                         return x
  78                 }
  79                 return y
  80         }
  81         if x < y {
  82                 return x
  83         }
  84         return y
  85 }