/* Copyright (C) 1989, 1992, 1993 Aladdin Enterprises.  All rights reserved.
  
  This file is part of Aladdin Ghostscript.
  
  Aladdin Ghostscript is distributed with NO WARRANTY OF ANY KIND.  No author
  or distributor accepts any responsibility for the consequences of using it,
  or for whether it serves any particular purpose or works at all, unless he
  or she says so in writing.  Refer to the Aladdin Ghostscript Free Public
  License (the "License") for full details.
  
  Every copy of Aladdin Ghostscript must include a copy of the License,
  normally in a plain ASCII text file named PUBLIC.  The License grants you
  the right to copy, modify and redistribute Aladdin Ghostscript, but only
  under certain conditions described in the License.  Among other things, the
  License requires that the copyright notice and this notice be preserved on
  all copies.
*/

/* zmath.c */
/* Mathematical operators */
#include "math_.h"
#include "ghost.h"
#include "errors.h"
#include "oper.h"
#include "store.h"

/* Current state of random number generator. */
/* We have to implement this ourselves because */
/* the Unix rand doesn't provide anything equivalent to rrand. */
/* Note that the value always lies in the range [0..0x7ffffffe], */
/* even if longs are longer than 32 bits. */
private long rand_state;

/* Initialize the random number generator. */
private void
zmath_init(void)
{	rand_state = 1;
}

/****** NOTE: none of these operators currently ******/
/****** check for floating over- or underflow.	******/

/* <num> sqrt <real> */
int
zsqrt(register os_ptr op)
{	float num;
	int code = num_params(op, 1, &num);
	if ( code < 0 )
		return code;
	if ( num < 0.0 )
		return_error(e_rangecheck);
	make_real(op, sqrt(num));
	return 0;
}

/* <num> arccos <real> */
int
zarccos(register os_ptr op)
{	float num, result;
	int code = num_params(op, 1, &num);
	if ( code < 0 ) return code;
	result = acos(num) * radians_to_degrees;
	make_real(op, result);
	return 0;
}

/* <num> arcsin <real> */
int
zarcsin(register os_ptr op)
{	float num, result;
	int code = num_params(op, 1, &num);
	if ( code < 0 ) return code;
	result = asin(num) * radians_to_degrees;
	make_real(op, result);
	return 0;
}

/* <num> <denom> atan <real> */
int
zatan(register os_ptr op)
{	float args[2];
	float result;
	int code = num_params(op, 2, args);
	if ( code < 0 ) return code;
	if ( args[0] == 0 )		/* on X-axis, special case */
	   {	if ( args[1] == 0 )
			return_error(e_undefinedresult);
		result = (args[1] < 0 ? 180 : 0);
	   }
	else
	   {	result = atan2(args[0], args[1]) * radians_to_degrees;
		if ( result < 0 ) result += 360;
	   }
	make_real(op - 1, result);
	pop(1);
	return 0;
}

/* <num> cos <real> */
int
zcos(register os_ptr op)
{	float angle;
	int code = num_params(op, 1, &angle);
	if ( code < 0 ) return code;
	make_real(op, cos(angle * degrees_to_radians));
	return 0;
}

/* <num> sin <real> */
int
zsin(register os_ptr op)
{	float angle;
	int code = num_params(op, 1, &angle);
	if ( code < 0 ) return code;
	make_real(op, sin(angle * degrees_to_radians));
	return 0;
}

/* <base> <exponent> exp <real> */
int
zexp(register os_ptr op)
{	float args[2];
	float result;
	double ipart;
	int code = num_params(op, 2, args);
	if ( code < 0 ) return code;
	if ( args[0] == 0.0 && args[1] == 0.0 )
		return_error(e_undefinedresult);
	if ( args[0] < 0.0 && modf(args[1], &ipart) != 0.0 )
		return_error(e_undefinedresult);
	result = pow(args[0], args[1]);
	make_real(op - 1, result);
	pop(1);
	return 0;
}

/* <posnum> ln <real> */
int
zln(register os_ptr op)
{	float num;
	int code = num_params(op, 1, &num);
	if ( code < 0 )
		return code;
	if ( num <= 0.0 )
		return_error(e_rangecheck);
	make_real(op, log(num));
	return 0;
}

/* <posnum> log <real> */
int
zlog(register os_ptr op)
{	float num;
	int code = num_params(op, 1, &num);
	if ( code < 0 )
		return code;
	if ( num <= 0.0 )
		return_error(e_rangecheck);
	make_real(op, log10(num));
	return 0;
}

/* - rand <int> */
int
zrand(register os_ptr op)
{	/*
	 * We use an algorithm from CACM 31 no. 10, pp. 1192-1201,
	 * October 1988.  According to a posting by Ed Taft on
	 * comp.lang.postscript, Level 2 (Adobe) PostScript interpreters
	 * use this algorithm too:
	 *	x[n+1] = (16807 * x[n]) mod (2^31 - 1)
	 */
#define A 16807
#define M 0x7fffffff
#define Q 127773			/* M / A */
#define R 2836				/* M % A */
	rand_state = A * (rand_state % Q) - R * (rand_state / Q);
	/* Note that rand_state cannot be 0 here. */
	if ( rand_state <= 0 ) rand_state += M;
#undef A
#undef M
#undef Q
#undef R
	push(1);
	make_int(op, rand_state);
	return 0;
}

/* <int> srand - */
int
zsrand(register os_ptr op)
{	long state;
	check_type(*op, t_integer);
	state = op->value.intval;
#if arch_sizeof_long > 4
	/* Trim the state back to 32 bits. */
	state = (int)state;
#endif
	/*
	 * The following somewhat bizarre adjustments are according to
	 * public information from Adobe describing their implementation.
	 */
	if ( state < 1 )
		state = -(state % 0x7ffffffe) + 1;
	else if ( state > 0x7ffffffe )
		state = 0x7ffffffe;
	rand_state = state;
	pop(1);
	return 0;
}

/* - rrand <int> */
int
zrrand(register os_ptr op)
{	push(1);
	make_int(op, rand_state);
	return 0;
}

/* ------ Initialization procedure ------ */

op_def zmath_op_defs[] = {
	{"1arccos", zarccos},		/* extension */
	{"1arcsin", zarcsin},		/* extension */
	{"2atan", zatan},
	{"1cos", zcos},
	{"2exp", zexp},
	{"1ln", zln},
	{"1log", zlog},
	{"0rand", zrand},
	{"0rrand", zrrand},
	{"1sin", zsin},
	{"1sqrt", zsqrt},
	{"1srand", zsrand},
	op_def_end(zmath_init)
};
