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Source file src/runtime/complex.go

  // 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
  
  func isposinf(f float64) bool { return f > maxFloat64 }
  func isneginf(f float64) bool { return f < -maxFloat64 }
  func isnan(f float64) bool    { return f != f }
  
  func nan() float64 {
  	var f float64 = 0
  	return f / f
  }
  
  func posinf() float64 {
  	var f float64 = maxFloat64
  	return f * f
  }
  
  func neginf() float64 {
  	var f float64 = maxFloat64
  	return -f * f
  }
  
  func complex128div(n complex128, d complex128) complex128 {
  	// Special cases as in C99.
  	ninf := isposinf(real(n)) || isneginf(real(n)) ||
  		isposinf(imag(n)) || isneginf(imag(n))
  	dinf := isposinf(real(d)) || isneginf(real(d)) ||
  		isposinf(imag(d)) || isneginf(imag(d))
  
  	nnan := !ninf && (isnan(real(n)) || isnan(imag(n)))
  	dnan := !dinf && (isnan(real(d)) || isnan(imag(d)))
  
  	switch {
  	case nnan || dnan:
  		return complex(nan(), nan())
  	case ninf && !dinf:
  		return complex(posinf(), posinf())
  	case !ninf && dinf:
  		return complex(0, 0)
  	case real(d) == 0 && imag(d) == 0:
  		if real(n) == 0 && imag(n) == 0 {
  			return complex(nan(), nan())
  		} else {
  			return complex(posinf(), posinf())
  		}
  	default:
  		// Standard complex arithmetic, factored to avoid unnecessary overflow.
  		a := real(d)
  		if a < 0 {
  			a = -a
  		}
  		b := imag(d)
  		if b < 0 {
  			b = -b
  		}
  		if a <= b {
  			ratio := real(d) / imag(d)
  			denom := real(d)*ratio + imag(d)
  			return complex((real(n)*ratio+imag(n))/denom,
  				(imag(n)*ratio-real(n))/denom)
  		} else {
  			ratio := imag(d) / real(d)
  			denom := imag(d)*ratio + real(d)
  			return complex((imag(n)*ratio+real(n))/denom,
  				(imag(n)-real(n)*ratio)/denom)
  		}
  	}
  }
  

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