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