// Copyright 2010 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 runtime
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// inf2one returns a signed 1 if f is an infinity and a signed 0 otherwise.
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// The sign of the result is the sign of f.
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func inf2one(f float64) float64 {
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g := 0.0
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if isInf(f) {
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g = 1.0
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}
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return copysign(g, f)
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}
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func complex128div(n complex128, m complex128) complex128 {
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var e, f float64 // complex(e, f) = n/m
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// Algorithm for robust complex division as described in
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// Robert L. Smith: Algorithm 116: Complex division. Commun. ACM 5(8): 435 (1962).
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if abs(real(m)) >= abs(imag(m)) {
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ratio := imag(m) / real(m)
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denom := real(m) + ratio*imag(m)
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e = (real(n) + imag(n)*ratio) / denom
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f = (imag(n) - real(n)*ratio) / denom
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} else {
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ratio := real(m) / imag(m)
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denom := imag(m) + ratio*real(m)
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e = (real(n)*ratio + imag(n)) / denom
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f = (imag(n)*ratio - real(n)) / denom
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}
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if isNaN(e) && isNaN(f) {
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// Correct final result to infinities and zeros if applicable.
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// Matches C99: ISO/IEC 9899:1999 - G.5.1 Multiplicative operators.
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a, b := real(n), imag(n)
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c, d := real(m), imag(m)
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switch {
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case m == 0 && (!isNaN(a) || !isNaN(b)):
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e = copysign(inf, c) * a
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f = copysign(inf, c) * b
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case (isInf(a) || isInf(b)) && isFinite(c) && isFinite(d):
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a = inf2one(a)
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b = inf2one(b)
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e = inf * (a*c + b*d)
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f = inf * (b*c - a*d)
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case (isInf(c) || isInf(d)) && isFinite(a) && isFinite(b):
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c = inf2one(c)
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d = inf2one(d)
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e = 0 * (a*c + b*d)
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f = 0 * (b*c - a*d)
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}
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}
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return complex(e, f)
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}
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