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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libgo/] [go/] [math/] [atan2.go] - Blame information for rev 867

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1 747 jeremybenn 
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package math
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// Atan2 returns the arc tangent of y/x, using
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// the signs of the two to determine the quadrant
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// of the return value.
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//
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// Special cases are (in order):
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//      Atan2(y, NaN) = NaN
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//      Atan2(NaN, x) = NaN
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//      Atan2(+0, x>=0) = +0
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//      Atan2(-0, x>=0) = -0
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//      Atan2(+0, x<=-0) = +Pi
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//      Atan2(-0, x<=-0) = -Pi
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//      Atan2(y>0, 0) = +Pi/2
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//      Atan2(y<0, 0) = -Pi/2
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//      Atan2(+Inf, +Inf) = +Pi/4
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//      Atan2(-Inf, +Inf) = -Pi/4
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//      Atan2(+Inf, -Inf) = 3Pi/4
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//      Atan2(-Inf, -Inf) = -3Pi/4
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//      Atan2(y, +Inf) = 0
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//      Atan2(y>0, -Inf) = +Pi
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//      Atan2(y<0, -Inf) = -Pi
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//      Atan2(+Inf, x) = +Pi/2
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//      Atan2(-Inf, x) = -Pi/2
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//extern atan2
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func libc_atan2(float64, float64) float64
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func Atan2(y, x float64) float64 {
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        return libc_atan2(y, x)
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}
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func atan2(y, x float64) float64 {
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        // special cases
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        switch {
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        case IsNaN(y) || IsNaN(x):
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                return NaN()
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        case y == 0:
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                if x >= 0 && !Signbit(x) {
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                        return Copysign(0, y)
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                }
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                return Copysign(Pi, y)
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        case x == 0:
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                return Copysign(Pi/2, y)
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        case IsInf(x, 0):
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                if IsInf(x, 1) {
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                        switch {
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                        case IsInf(y, 0):
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                                return Copysign(Pi/4, y)
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                        default:
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                                return Copysign(0, y)
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                        }
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                }
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                switch {
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                case IsInf(y, 0):
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                        return Copysign(3*Pi/4, y)
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                default:
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                        return Copysign(Pi, y)
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                }
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        case IsInf(y, 0):
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                return Copysign(Pi/2, y)
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        }
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        // Call atan and determine the quadrant.
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        q := Atan(y / x)
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        if x < 0 {
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                if q <= 0 {
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                        return q + Pi
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                }
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                return q - Pi
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        }
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        return q
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}

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