1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
| // Copyright 2009 The Go Authors. All rights reserved.
| // Use of this source code is governed by a BSD-style
| // license that can be found in the LICENSE file.
|
| package math
|
| // Atan2 returns the arc tangent of y/x, using
| // the signs of the two to determine the quadrant
| // of the return value.
| //
| // Special cases are (in order):
| // Atan2(y, NaN) = NaN
| // Atan2(NaN, x) = NaN
| // Atan2(+0, x>=0) = +0
| // Atan2(-0, x>=0) = -0
| // Atan2(+0, x<=-0) = +Pi
| // Atan2(-0, x<=-0) = -Pi
| // Atan2(y>0, 0) = +Pi/2
| // Atan2(y<0, 0) = -Pi/2
| // Atan2(+Inf, +Inf) = +Pi/4
| // Atan2(-Inf, +Inf) = -Pi/4
| // Atan2(+Inf, -Inf) = 3Pi/4
| // Atan2(-Inf, -Inf) = -3Pi/4
| // Atan2(y, +Inf) = 0
| // Atan2(y>0, -Inf) = +Pi
| // Atan2(y<0, -Inf) = -Pi
| // Atan2(+Inf, x) = +Pi/2
| // Atan2(-Inf, x) = -Pi/2
| func Atan2(y, x float64) float64
|
| func atan2(y, x float64) float64 {
| // special cases
| switch {
| case IsNaN(y) || IsNaN(x):
| return NaN()
| case y == 0:
| if x >= 0 && !Signbit(x) {
| return Copysign(0, y)
| }
| return Copysign(Pi, y)
| case x == 0:
| return Copysign(Pi/2, y)
| case IsInf(x, 0):
| if IsInf(x, 1) {
| switch {
| case IsInf(y, 0):
| return Copysign(Pi/4, y)
| default:
| return Copysign(0, y)
| }
| }
| switch {
| case IsInf(y, 0):
| return Copysign(3*Pi/4, y)
| default:
| return Copysign(Pi, y)
| }
| case IsInf(y, 0):
| return Copysign(Pi/2, y)
| }
|
| // Call atan and determine the quadrant.
| q := Atan(y / x)
| if x < 0 {
| if q <= 0 {
| return q + Pi
| }
| return q - Pi
| }
| return q
| }
|
|
