hypot.3m

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 3M 代码 · 共 74 行

.TH hypot 3m RISC
.ds up \fIulp\fR
.ds nn \fINaN\fR
.SH Name
hypot, cabs \- Euclidean distance, complex absolute value
.SH Syntax
.nf
.B #include <math.h>
.PP
.B double hypot(\fIx,y\fP)
.B double \fIx,y;
.PP
.B float fhypot(float x, float y)
.PP
.B double cabs(\fIz\fP)
.B struct {double x,y;} \fIz\fP;
.PP
.B float fcabs(\fIz\fP)
.B struct {float x,y;} \fIz\fP;
.fi
.SH Description
.NXR "hypot function"
.NXR "cabs function"
The 
.PN hypot ,
.PN fhypot ,
.PN cabs ,
and
.PN fcabs
functions return the following:
.EX
sqrt(x\(**x+y\(**y)
.EE
This computation prevents underflows and overflows only if
the final result dictates it.
.PP
The functions
.PN fhypot
and
.PN fcabs
are equivalent to the
.PN hypot
and
.PN cabs
function with the exception of float data type.
.SS Error 
When rounding off, for example, below 0.97 \*(ups.  Consequently
.PN hypot
(5.0,12.0)\0=\013.0 exactly;
in general,
.PN hypot
and
.PN cabs
return an integer whenever an integer might be expected.
.PP
The same cannot be said for the shorter and faster version of
.PN hypot
and
.PN cabs
that is provided in the comments in cabs.c; its error can
exceed 1.2 \*(ups.
.SH Return Values
If the correct value overflows, 
.PN hypot
and
.PN cabs
return HUGE_VAL.   If
.I x
or
.I y
is \*(nn, then \*(nn is returned.
.SH See Also
math(3m), sqrt(3m)