/************************************************************************
 *									*
 *				N O T I C E				*
 *									*
 *			Copyright Abandoned, 1987, Fred Fish		*
 *									*
 *	This previously copyrighted work has been placed into the	*
 *	public domain by the author (Fred Fish) and may be freely used	*
 *	for any purpose, private or commercial.  I would appreciate	*
 *	it, as a courtesy, if this notice is left in all copies and	*
 *	derivative works.  Thank you, and enjoy...			*
 *									*
 *	The author makes no warranty of any kind with respect to this	*
 *	product and explicitly disclaims any implied warranties of	*
 *	merchantability or fitness for any particular purpose.		*
 *									*
 ************************************************************************
 */


/*
 *  FUNCTION
 *
 *	tan   Double precision tangent
 *
 *  KEY WORDS
 *
 *	tan
 *	machine independent routines
 *	trigonometric functions
 *	math libraries
 *
 *  DESCRIPTION
 *
 *	Returns tangent of double precision floating point number.
 *
 *  USAGE
 *
 *	double tan (x)
 *	double x;
 *
 *  INTERNALS
 *
 *	Computes the tangent from tan(x) = sin(x) / cos(x).
 *
 *	If cos(x) = 0 and sin(x) >= 0, then returns largest
 *	floating point number on host machine.
 *
 *	If cos(x) = 0 and sin(x) < 0, then returns smallest
 *	floating point number on host machine.
 *
 *  REFERENCES
 *
 *	Fortran IV plus user's guide, Digital Equipment Corp. pp. B-8
 *
 */

#if !defined (__M68881__) && !defined (sfp004)	/* mjr++		*/

#include <stdio.h>
#include <math.h>
#include "pml.h"

static char funcname[] = "tan";

double tan (x)
double x;
{
    double sinx;
    double cosx;
    struct exception xcpt;

    sinx = sin (x);
    cosx = cos (x);
    if (cosx == 0.0) {
	xcpt.type = OVERFLOW;
	xcpt.name = funcname;
	xcpt.arg1 = x;
	if (!matherr (&xcpt)) {
	    fprintf (stderr, "%s: OVERFLOW error\n", funcname);
	    errno = ERANGE;
	    if (sinx >= 0.0) {
		xcpt.retval = HUGE_VAL;
	    } else {
		xcpt.retval = -HUGE_VAL;
	    }
	}
    } else {
	xcpt.retval = sinx / cosx;
    }
    return (xcpt.retval);
}

#endif	/* __M68881__ || sfp004	*/
#ifdef	sfp004

__asm("

comm =	 -6
resp =	-16
zahl =	  0

");	/* end asm	*/

#endif	sfp004
#if defined (__M68881__) || defined (sfp004)

    __asm(".text; .even");

# ifdef	ERROR_CHECK

    __asm("

_Overflow:
	.ascii \"OVERFLOW\\0\"
_Domain:
	.ascii \"DOMAIN\\0\"
_Error_String:
	.ascii \"tan: %s error\\n\\0\"
.even
| pml compatible tangent
| m.ritzert 7.12.1991
| ritzert@dfg.dbp.de
|
|    /* NAN  = {7fffffff,ffffffff}		*/
|    /* +Inf = {7ff00000,00000000}		*/
|    /* -Inf = {fff00000,00000000}		*/
|    /* MAX_D= {7fee42d1,30773b76}		*/
|    /* MIN_D= {ffee42d1,30773b76}		*/

.even
double_max:
	.long	0x7fee42d1
	.long	0x30273b76
double_min:
	.long	0xffee42d1
	.long	0x30273b76
NaN:
	.long	0x7fffffff
	.long	0xffffffff
p_Inf:
	.long	0x7ff00000
	.long	0x00000000
m_Inf:
	.long	0xfff00000
	.long	0x00000000
");
# endif	ERROR_CHECK

    __asm(".even
.globl _tan
_tan:
    ");	/* end asm	*/

#endif	/* __M68881__ || sfp004	*/
#ifdef	__M68881__

    __asm("
	ftand	a7@(4), fp0	| tan
	fmoved	fp0,a7@-	| push result
	moveml	a7@+,d0-d1	| return_value
    ");	/* end asm	*/

#endif	__M68881__
#ifdef	sfp004
    __asm("
	lea	0xfffa50,a0
	movew	#0x540f,a0@(comm)	| specify function
	cmpiw	#0x8900,a0@(resp)	| check
	movel	a7@(4),a0@		| load arg_hi
	movel	a7@(8),a0@		| load arg_low
	movew	#0x7400,a0@(comm)	| result to d0
	.long	0x0c688900, 0xfff067f8	| wait
	movel	a0@,d0
	movel	a0@,d1
    ");	/* end asm	*/

#endif	sfp004
#if defined (__M68881__) || defined (sfp004)
# ifdef	ERROR_CHECK
    __asm("
	lea	double_max,a0	|
	swap	d0		| exponent into lower word
	cmpw	a0@(16),d0	| == NaN ?
	beq	error_nan	|
	cmpw	a0@(24),d0	| == + Infinity ?
	beq	error_plus	|
	cmpw	a0@(32),d0	| == - Infinity ?
	beq	error_minus	|
	swap	d0		| result ok,
	rts			| restore d0
");
#ifndef	__MSHORT__
__asm("
error_minus:
	swap	d0
	moveml	d0-d1,a7@-
	movel	#63,_errno	| errno = ERANGE
	pea	_Overflow	| for printf
	bra	error_exit	|
error_plus:
	swap	d0
	moveml	d0-d1,a7@-
	movel	#63,_errno	| NAN => errno = EDOM
	pea	_Overflow	| for printf
	bra	error_exit	|
error_nan:
	moveml	a0@(24),d0-d1	| result = +inf
	moveml	d0-d1,a7@-
	movel	#62,_errno	| NAN => errno = EDOM
	pea	_Domain		| for printf
");
#else	__MSHORT__
__asm("
error_minus:
	swap	d0
	moveml	d0-d1,a7@-
	movew	#63,_errno	| errno = ERANGE
	pea	_Overflow	| for printf
	bra	error_exit	|
error_plus:
	swap	d0
	moveml	d0-d1,a7@-
	movew	#63,_errno	| NAN => errno = EDOM
	pea	_Overflow	| for printf
	bra	error_exit	|
error_nan:
	moveml	a0@(24),d0-d1	| result = +inf
	moveml	d0-d1,a7@-
	movew	#62,_errno	| NAN => errno = EDOM
	pea	_Domain		| for printf
");
#endif	__MSHORT__
__asm("
error_exit:
	pea	_Error_String	|
	pea	__iob+52	|
	jbsr	_fprintf	|
	addl	#12,a7		|
	moveml	a7@+,d0-d1
	rts
    ");
# else	ERROR_CHECK
__asm("rts");
# endif	ERROR_CHECK

#endif /* __M68881__ || sfp004	*/