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

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