From 47ab3d4a42e9ab51c465c4322d2ec233f6324e6b Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 28 Apr 2024 15:16:40 +0200 Subject: Adding upstream version 1.18.10. Signed-off-by: Daniel Baumann --- src/math/atan2.go | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 76 insertions(+) create mode 100644 src/math/atan2.go (limited to 'src/math/atan2.go') diff --git a/src/math/atan2.go b/src/math/atan2.go new file mode 100644 index 0000000..11d7e81 --- /dev/null +++ b/src/math/atan2.go @@ -0,0 +1,76 @@ +// 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 { + if haveArchAtan2 { + return archAtan2(y, x) + } + return atan2(y, x) +} + +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 +} -- cgit v1.2.3