Source file src/pkg/math/hypot.go

     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 computes Sqrt(p*p + q*q), taking care to avoid
    12	// unnecessary overflow and underflow.
    13	//
    14	// Special cases are:
    15	//	Hypot(p, q) = +Inf if p or q is infinite
    16	//	Hypot(p, q) = NaN if p or q is NaN
    17	func Hypot(p, q float64) float64
    18	
    19	func hypot(p, q float64) float64 {
    20		// special cases
    21		switch {
    22		case IsInf(p, 0) || IsInf(q, 0):
    23			return Inf(1)
    24		case IsNaN(p) || IsNaN(q):
    25			return NaN()
    26		}
    27		if p < 0 {
    28			p = -p
    29		}
    30		if q < 0 {
    31			q = -q
    32		}
    33		if p < q {
    34			p, q = q, p
    35		}
    36		if p == 0 {
    37			return 0
    38		}
    39		q = q / p
    40		return p * Sqrt(1+q*q)
    41	}