NAME
hypot, hypotf, hypotl, cabs, cabsf, cabsl – Euclidean distance and complex absolute value functions
LIBRARY
Math Library (libm, -lm)
SYNOPSIS
#include <math.h>
double
hypot(double x, double y);
float
hypotf(float x, float y);
long double
hypotl(long double x, long double y);
#include <complex.h>
double
cabs(double complex z);
float
cabsf(float complex z);
long double
cabsl(long double complex z);
DESCRIPTION
The hypot(), hypotf() and hypotl() functions compute the sqrt(x*x+y*y) in such a way that underflow will not happen, and overflow occurs only if the final result deserves it. The cabs(), cabsf() and cabsl() functions compute the complex absolute value of z.
hypot(, v) = hypot(v, ) = + for all v, including .
ERROR (due to Roundoff, etc.)
Below 0.97 ulps. Consequently hypot(5.0, 12.0) = 13.0 exactly; in general, hypot and cabs return an integer whenever an integer might be expected.
NOTES
As might be expected, hypot(v, ) and hypot(, v) are for all finite v. But programmers might be surprised at first to discover that hypot(±, ) = +. This is intentional; it happens because hypot(, v) = + for all v, finite or infinite. Hence hypot(, v) is independent of v. Unlike the reserved operand fault on a VAX, the IEEE
is designed to disappear when it turns out to be irrelevant, as it does in hypot(, ).
SEE ALSO
STANDARDS
The hypot(), hypotf(), hypotl(), cabs(), cabsf(), and cabsl() functions conform to ISO/IEC 9899:1999 (“ISO C99”).
HISTORY
Both a hypot() function and a cabs() function appeared in Version 7 AT&T UNIX.