double
hypot(
double x
, double y
)
float
hypotf(
float x
, float y
)
)
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 .
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.
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(
,
).
)
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.