HYPOT(3) BSD Library Functions Manual HYPOT(3)NAME
hypot, hypotf — 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);
DESCRIPTION
The hypot() functions compute the sqrt(x*x+y*y) in such a way that under‐
flow will not happen, and overflow occurs only if the final result
deserves it.
hypot(∞, v) = hypot(v, ∞) = +∞ for all v, including NaN.
ERRORS
Below 0.97 ulps. Consequently hypot(5.0, 12.0) = 13.0 exactly; in gen‐
eral, hypot returns an integer whenever an integer might be expected.
The same cannot be said for the shorter and faster version of hypot that
is provided in the comments in cabs.c; its error can exceed 1.2 ulps.
NOTES
As might be expected, hypot(v, NaN) and hypot(NaN, v) are NaN for all
finite v; with "reserved operand" in place of "NaN", the same is true on
a VAX. But programmers on machines other than a VAX (it has no ∞) might
be surprised at first to discover that hypot(±∞, NaN) = +∞. 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 NaN is designed to disappear when it
turns out to be irrelevant, as it does in hypot(∞, NaN).
SEE ALSOmath(3), sqrt(3)HISTORY
Both a hypot() function and a cabs() function appeared in Version 7 AT&T
UNIX. cabs() was removed from public namespace in NetBSD 5.0 to avoid
conflicts with the complex function in C99.
BSD February 12, 2007 BSD