HYPOT(3M)							     HYPOT(3M)

NAME    [Toc]    [Back]

     hypot, hypotf, fhypot, hypotl, cabs, cabsf, fcabs,	cabsl -	Euclidean
     distance, complex absolute	value

SYNOPSIS    [Toc]    [Back]

     #include <math.h>

     double hypot (double x, double y);
     float fhypot (float x, float y);
     float hypotf (float x, float y);
     long double hypotl	(long double x,	long double y);

     double cabs (struct { double a,b; } z);
     float fcabs (struct { float a,b; }	z);
     float cabsf (struct { float a,b; }	z);
     long double cabsl (struct { long double a,b; } z);

DESCRIPTION    [Toc]    [Back]

     hypot(x,y), fhypot(x,y), hypotf(x,y), hypotl(x,y),	cabs(x,y), fcabs(x,y),
     cabsf(x,y), and cabsl(x,y)	return sqrt(x*x+y*y) computed in such a	way
     that overflow will	not happen, and	underflow occurs only if the final
     result deserves it.

     fhypot, hypotf, fcabs, and	cabsf are the same functions as	hypot and cabs
     but for the float data type.

     hypotl, and cabsl are the same functions as hypot and cabs	but for	the
     long double data type.

DIAGNOSTICS    [Toc]    [Back]

     In	the diagnostics	below, functions in the	standard math library libm.a,
     are referred to as	-lm versions, those in libmx.a are referred to as -lmx
     versions, and those in the	the BSD	math library libm43.a, are referred to
     as	-lm43 versions.	 The -lm and -lmx versions always return the default
     Quiet NaN and set errno to	EDOM when a NaN	is used	as an argument.	 A NaN
     argument causes the -lm43 versions	of the hypot functions to return the
     same NaN, unless the other	argument is HUGE_VAL, in which case HUGE_VAL
     is	returned.  The -lm43 versions never set	errno.	The value of HUGE_VAL
     is	IEEE Infinity.

     When the correct value would overflow, the	hypot functions	return
     HUGE_VAL  The -lm and -lmx	versions also set errno	to ERANGE.  See
     matherr(3M) for a description of error handling for -lmx functions.

NOTES    [Toc]    [Back]

     Long double operations on this system are only supported in round to
     nearest rounding mode (the	default).  The system must be in round to
     nearest rounding mode when	calling	any of the long	double functions, or
     incorrect answers will result.






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HYPOT(3M)							     HYPOT(3M)



     Users concerned with portability to other computer	systems	should note
     that the long double and float versions of	these functions	are optional
     according to the ANSI C Programming Language Specification	ISO/IEC	9899 :
     1990 (E).

     Long double functions have	been renamed to	be compliant with the ANSI-C
     standard, however to be backward compatible, they may still be called
     with the double precision function	name prefixed with a q.

     hypot and cabs are	not ANSI-C functions.  If you compile with flag	-ansi,
     you must supply your own prototypes for these functions or	you will get
     incorrect results.	 (See the prototypes defined in	/usr/include/math.h)

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.

SEE ALSO    [Toc]    [Back]

     math(3M), sqrt(3M), matherr(3M)

AUTHOR    [Toc]    [Back]

     W.	Kahan


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