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PDP-10 Archives
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SRI_NIC_PERM_FS_1_19910112
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kcc-4/lib/pml/dtanh.c
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/*
* +++ NAME +++
*
* DTANH Double precision hyperbolic tangent
*
* +++ INDEX +++
*
* DTANH
* machine independent routines
* math libraries
*
* +++ DESCRIPTION +++
*
* Returns double precision hyperbolic tangent of double precision
* floating point number.
*
* +++ USAGE +++
*
* double dtanh(x)
* double x;
*
* +++ REFERENCES +++
*
* Fortran IV plus user's guide, Digital Equipment Corp. pp B-5
*
* +++ RESTRICTIONS +++
*
* For precision information refer to documentation of the
* floating point library routines called.
*
* +++ PROGRAMMER +++
*
* Fred Fish
* Goodyear Aerospace Corp, Arizona Div.
* (602) 932-7000 work
* (602) 894-6881 home
*
* +++ INTERNALS +++
*
* Computes hyperbolic tangent from:
*
* DTANH(X) = 1.0 for X > DTANH_MAXARG
* = -1.0 for X < -DTANH_MAXARG
* = DSINH(X) / DCOSH(X) otherwise
*
* ---
*/
/*)LIBRARY
*/
#include <stdio.h>
#include "c:pmluse.h"
#include "pml.h"
double dtanh(x)
double x;
{
double dsinh(), dcosh();
if (x > DTANH_MAXARG) {
return(1.0);
} else if (x < -DTANH_MAXARG) {
return(-1.0);
} else {
return( dsinh(x) / dcosh(x) );
}
}