

 
Manual Reference Pages  CABS (3)
NAME
hypot,
hypotf,
hypotl,
cabs,
cabsf,
cabsl
 Euclidean distance and complex absolute value functions
CONTENTS
Library
Synopsis
Description
ERROR (due to Roundoff, etc.)
Notes
See Also
Standards
History
LIBRARY
.Lb libm
SYNOPSIS
.In math.h
double
hypot double x double y
float
hypotf float x float y
long double
hypotl long double x long double y
.In 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 oo v
=
hypot v oo
= +oo for all
v,
including NaN.
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 NaN
and
hypot NaN v
are NaN for all
finite
v.
But programmers
might be surprised at first to discover that
hypot ±oo NaN
= +oo.
This is intentional; it happens because
hypot oo v
= +oo
for
all
v,
finite or infinite.
Hence
hypot oo 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 oo NaN.
SEE ALSO
carg(3),
math(3),
sqrt(3)
STANDARDS
The
hypot,
hypotf,
hypotl,
cabs,
cabsf,
and
cabsl
functions conform to
isoC99.
HISTORY
Both a
hypot
function and a
cabs
function
appeared in
AT&T v7 .
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