NAME

hypot, hypotf - Euclidean distance and complex absolute value functions

LIBRARY

Math Library (libm, -lm)

SYNOPSIS



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 underflow will not happen, and overflow occurs only if the final result deserves it.

hypot(, v) = hypot(v, ) = + for all v, including .

ERRORS

Below 0.97 ulps. Consequently hypot(5.0, 12.0) = 13.0 exactly; in general, 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, ) and hypot(, v) are for all finite v; with "reserved operand" in place of "", 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(±, ) = +. 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

math(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 NetBSD5.0 to avoid conflicts with the complex function in C99.