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.\"     from: @(#)hypot.3	6.7 (Berkeley) 5/6/91
.\"
.Dd March 30, 2008
.Dt HYPOT 3
.Os
.Sh NAME
.Nm hypot ,
.Nm hypotf ,
.Nm hypotl ,
.Nm cabs ,
.Nm cabsf ,
.Nm cabsl
.Nd Euclidean distance and complex absolute value functions
.Sh LIBRARY
.Lb libm
.Sh SYNOPSIS
.In math.h
.Ft double
.Fn hypot "double x" "double y"
.Ft float
.Fn hypotf "float x" "float y"
.Ft "long double"
.Fn hypotl "long double x" "long double y"
.In complex.h
.Ft double
.Fn cabs "double complex z"
.Ft float
.Fn cabsf "float complex z"
.Ft "long double"
.Fn cabsl "long double complex z"
.Sh DESCRIPTION
The
.Fn hypot ,
.Fn hypotf
and
.Fn 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
.Fn cabs ,
.Fn cabsf
and
.Fn cabsl
functions compute the complex absolute value of
.Fa z .
.Pp
.Fn hypot "\*(If" "v"
=
.Fn hypot "v" "\*(If"
= +\*(If for all
.Fa v ,
including \*(Na.
.Sh ERROR (due to Roundoff, etc.)
Below 0.97
.Em ulps .
Consequently
.Fn hypot "5.0" "12.0"
= 13.0
exactly;
in general, hypot and cabs return an integer whenever an
integer might be expected.
.Sh NOTES
As might be expected,
.Fn hypot "v" "\*(Na"
and
.Fn hypot "\*(Na" "v"
are \*(Na for all
.Em finite
.Fa v .
But programmers
might be surprised at first to discover that
.Fn hypot "\(+-\*(If" "\*(Na"
= +\*(If.
This is intentional; it happens because
.Fn hypot "\*(If" "v"
= +\*(If
for
.Em all
.Fa v ,
finite or infinite.
Hence
.Fn hypot "\*(If" "v"
is independent of
.Fa v .
Unlike the reserved operand fault on a
.Tn VAX ,
the
.Tn IEEE
\*(Na is designed to
disappear when it turns out to be irrelevant, as it does in
.Fn hypot "\*(If" "\*(Na" .
.Sh SEE ALSO
.Xr carg 3 ,
.Xr math 3 ,
.Xr sqrt 3
.Sh STANDARDS
The
.Fn hypot ,
.Fn hypotf ,
.Fn hypotl ,
.Fn cabs ,
.Fn cabsf ,
and
.Fn cabsl
functions conform to
.St -isoC-99 .
.Sh HISTORY
Both a
.Fn hypot
function and a
.Fn cabs
function
appeared in
.At v7 .