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 //
11 // Dim(+Inf, +Inf) = NaN
12 // Dim(-Inf, -Inf) = NaN
13 // Dim(x, NaN) = Dim(NaN, x) = NaN
14 func Dim(x, y float64) float64 {
15 // The special cases result in NaN after the subtraction:
16 // +Inf - +Inf = NaN
17 // -Inf - -Inf = NaN
18 // NaN - y = NaN
19 // x - NaN = NaN
20 v := x - y
21 if v <= 0 {
22 // v is negative or 0
23 return 0
24 }
25 // v is positive or NaN
26 return v
27 }
28 29 // Max returns the larger of x or y.
30 //
31 // Special cases are:
32 //
33 // Max(x, +Inf) = Max(+Inf, x) = +Inf
34 // Max(x, NaN) = Max(NaN, x) = NaN
35 // Max(+0, ±0) = Max(±0, +0) = +0
36 // Max(-0, -0) = -0
37 //
38 // Note that this differs from the built-in function max when called
39 // with NaN and +Inf.
40 func Max(x, y float64) float64 {
41 if haveArchMax {
42 return archMax(x, y)
43 }
44 return max(x, y)
45 }
46 47 func max(x, y float64) float64 {
48 // special cases
49 switch {
50 case IsInf(x, 1) || IsInf(y, 1):
51 return Inf(1)
52 case IsNaN(x) || IsNaN(y):
53 return NaN()
54 case x == 0 && x == y:
55 if Signbit(x) {
56 return y
57 }
58 return x
59 }
60 if x > y {
61 return x
62 }
63 return y
64 }
65 66 // Min returns the smaller of x or y.
67 //
68 // Special cases are:
69 //
70 // Min(x, -Inf) = Min(-Inf, x) = -Inf
71 // Min(x, NaN) = Min(NaN, x) = NaN
72 // Min(-0, ±0) = Min(±0, -0) = -0
73 //
74 // Note that this differs from the built-in function min when called
75 // with NaN and -Inf.
76 func Min(x, y float64) float64 {
77 if haveArchMin {
78 return archMin(x, y)
79 }
80 return min(x, y)
81 }
82 83 func min(x, y float64) float64 {
84 // special cases
85 switch {
86 case IsInf(x, -1) || IsInf(y, -1):
87 return Inf(-1)
88 case IsNaN(x) || IsNaN(y):
89 return NaN()
90 case x == 0 && x == y:
91 if Signbit(x) {
92 return x
93 }
94 return y
95 }
96 if x < y {
97 return x
98 }
99 return y
100 }
101