github.com/prattmic/llgo-embedded@v0.0.0-20150820070356-41cfecea0e1e/third_party/gofrontend/libgo/go/math/hypot.go (about)

     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 math
     6  
     7  /*
     8  	Hypot -- sqrt(p*p + q*q), but overflows only if the result does.
     9  */
    10  
    11  // Hypot returns Sqrt(p*p + q*q), taking care to avoid
    12  // unnecessary overflow and underflow.
    13  //
    14  // Special cases are:
    15  //	Hypot(±Inf, q) = +Inf
    16  //	Hypot(p, ±Inf) = +Inf
    17  //	Hypot(NaN, q) = NaN
    18  //	Hypot(p, NaN) = NaN
    19  func Hypot(p, q float64) float64 {
    20  	return hypot(p, q)
    21  }
    22  
    23  func hypot(p, q float64) float64 {
    24  	// special cases
    25  	switch {
    26  	case IsInf(p, 0) || IsInf(q, 0):
    27  		return Inf(1)
    28  	case IsNaN(p) || IsNaN(q):
    29  		return NaN()
    30  	}
    31  	if p < 0 {
    32  		p = -p
    33  	}
    34  	if q < 0 {
    35  		q = -q
    36  	}
    37  	if p < q {
    38  		p, q = q, p
    39  	}
    40  	if p == 0 {
    41  		return 0
    42  	}
    43  	q = q / p
    44  	return p * Sqrt(1+q*q)
    45  }