Category : C Source Code
Archive   : CEPHES22.ZIP
Filename : COSHL.C

/* coshl.c
*
* Hyperbolic cosine, long double precision
*
*
*
* SYNOPSIS:
*
* long double x, y, coshl();
*
* y = coshl( x );
*
*
*
* DESCRIPTION:
*
* Returns hyperbolic cosine of argument in the range MINLOGL to
* MAXLOGL.
*
* cosh(x) = ( exp(x) + exp(-x) )/2.
*
*
*
* ACCURACY:
*
* Relative error:
* arithmetic domain # trials peak rms
* IEEE +-10000 30000 1.1e-19 2.8e-20
*
*
* ERROR MESSAGES:
*
* message condition value returned
* cosh overflow |x| > MAXLOGL MAXNUML
*
*
*/


/*
Cephes Math Library Release 2.2: January, 1991
Copyright 1985, 1991 by Stephen L. Moshier
Direct inquiries to 30 Frost Street, Cambridge, MA 02140
*/

#include "mconf.h"
extern long double MAXLOGL, MAXNUML;

long double coshl(x)
long double x;
{
long double y;
long double expl(), ldexpl();

if( x < 0 )
x = -x;
if( x > MAXLOGL )
{
mtherr( "coshl", OVERFLOW );
return( MAXNUML );
}
y = expl(x);
y = y + 1.0L/y;
y = ldexpl( y, -1 );
return( y );
}