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  	if haveArchMax {
    37  		return archMax(x, y)
    38  	}
    39  	return max(x, y)
    40  }
    41  
    42  func max(x, y float64) float64 {
    43  	// special cases
    44  	switch {
    45  	case IsInf(x, 1) || IsInf(y, 1):
    46  		return Inf(1)
    47  	case IsNaN(x) || IsNaN(y):
    48  		return NaN()
    49  	case x == 0 && x == y:
    50  		if Signbit(x) {
    51  			return y
    52  		}
    53  		return x
    54  	}
    55  	if x > y {
    56  		return x
    57  	}
    58  	return y
    59  }
    60  
    61  // Min returns the smaller of x or y.
    62  //
    63  // Special cases are:
    64  //	Min(x, -Inf) = Min(-Inf, x) = -Inf
    65  //	Min(x, NaN) = Min(NaN, x) = NaN
    66  //	Min(-0, ±0) = Min(±0, -0) = -0
    67  func Min(x, y float64) float64 {
    68  	if haveArchMin {
    69  		return archMin(x, y)
    70  	}
    71  	return min(x, y)
    72  }
    73  
    74  func min(x, y float64) float64 {
    75  	// special cases
    76  	switch {
    77  	case IsInf(x, -1) || IsInf(y, -1):
    78  		return Inf(-1)
    79  	case IsNaN(x) || IsNaN(y):
    80  		return NaN()
    81  	case x == 0 && x == y:
    82  		if Signbit(x) {
    83  			return x
    84  		}
    85  		return y
    86  	}
    87  	if x < y {
    88  		return x
    89  	}
    90  	return y
    91  }
    92
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