1 // Copyright 2010 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package runtime 6 7 func isposinf(f float64) bool { return f > maxFloat64 } 8 func isneginf(f float64) bool { return f < -maxFloat64 } 9 func isnan(f float64) bool { return f != f } 10 11 func nan() float64 { 12 var f float64 = 0 13 return f / f 14 } 15 16 func posinf() float64 { 17 var f float64 = maxFloat64 18 return f * f 19 } 20 21 func neginf() float64 { 22 var f float64 = maxFloat64 23 return -f * f 24 } 25 26 func complex128div(n complex128, d complex128) complex128 { 27 // Special cases as in C99. 28 ninf := isposinf(real(n)) || isneginf(real(n)) || 29 isposinf(imag(n)) || isneginf(imag(n)) 30 dinf := isposinf(real(d)) || isneginf(real(d)) || 31 isposinf(imag(d)) || isneginf(imag(d)) 32 33 nnan := !ninf && (isnan(real(n)) || isnan(imag(n))) 34 dnan := !dinf && (isnan(real(d)) || isnan(imag(d))) 35 36 switch { 37 case nnan || dnan: 38 return complex(nan(), nan()) 39 case ninf && !dinf: 40 return complex(posinf(), posinf()) 41 case !ninf && dinf: 42 return complex(0, 0) 43 case real(d) == 0 && imag(d) == 0: 44 if real(n) == 0 && imag(n) == 0 { 45 return complex(nan(), nan()) 46 } else { 47 return complex(posinf(), posinf()) 48 } 49 default: 50 // Standard complex arithmetic, factored to avoid unnecessary overflow. 51 a := real(d) 52 if a < 0 { 53 a = -a 54 } 55 b := imag(d) 56 if b < 0 { 57 b = -b 58 } 59 if a <= b { 60 ratio := real(d) / imag(d) 61 denom := real(d)*ratio + imag(d) 62 return complex((real(n)*ratio+imag(n))/denom, 63 (imag(n)*ratio-real(n))/denom) 64 } else { 65 ratio := imag(d) / real(d) 66 denom := imag(d)*ratio + real(d) 67 return complex((imag(n)*ratio+real(n))/denom, 68 (imag(n)-real(n)*ratio)/denom) 69 } 70 } 71 } 72
