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  she says so in writing.  Refer to the Aladdin Free Public License (the
  "License") for full details.
  
  Every copy of AFPL 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 AFPL Ghostscript, but only under certain
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  requires that the copyright notice and this notice be preserved on all
  copies.
*/

/*$Id: zmath.c,v 1.3 2000/09/19 19:00:54 lpd Exp $ */
/* Mathematical operators */
#include "math_.h"
#include "ghost.h"
#include "gxfarith.h"
#include "oper.h"
#include "store.h"

/*
 * Many of the procedures in this file are public only so they can be
 * called from the FunctionType 4 interpreter (zfunc4.c).
 */

/*
 * Define the current state of random number generator for operators.  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.
 *
 * The state must be public so that context switching can save and
 * restore it.  (Even though the Red Book doesn't mention this,
 * we verified with Adobe that this is the case.)
 */
#define zrand_state (i_ctx_p->rand_state)

/* Initialize the random number generator. */
const long rand_state_initial = 1;

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

/* <num> sqrt <real> */
int
zsqrt(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double num;
    int code = real_param(op, &num);

    if (code < 0)
	return code;
    if (num < 0.0)
	return_error(e_rangecheck);
    make_real(op, sqrt(num));
    return 0;
}

/* <num> arccos <real> */
private int
zarccos(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double num, result;
    int code = real_param(op, &num);

    if (code < 0)
	return code;
    result = acos(num) * radians_to_degrees;
    make_real(op, result);
    return 0;
}

/* <num> arcsin <real> */
private int
zarcsin(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double num, result;
    int code = real_param(op, &num);

    if (code < 0)
	return code;
    result = asin(num) * radians_to_degrees;
    make_real(op, result);
    return 0;
}

/* <num> <denom> atan <real> */
int
zatan(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double args[2];
    double result;
    int code = num_params(op, 2, args);

    if (code < 0)
	return code;
    code = gs_atan2_degrees(args[0], args[1], &result);
    if (code < 0)
	return code;
    make_real(op - 1, result);
    pop(1);
    return 0;
}

/* <num> cos <real> */
int
zcos(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double angle;
    int code = real_param(op, &angle);

    if (code < 0)
	return code;
    make_real(op, gs_cos_degrees(angle));
    return 0;
}

/* <num> sin <real> */
int
zsin(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double angle;
    int code = real_param(op, &angle);

    if (code < 0)
	return code;
    make_real(op, gs_sin_degrees(angle));
    return 0;
}

/* <base> <exponent> exp <real> */
int
zexp(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double args[2];
    double 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(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double num;
    int code = real_param(op, &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(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double num;
    int code = real_param(op, &num);

    if (code < 0)
	return code;
    if (num <= 0.0)
	return_error(e_rangecheck);
    make_real(op, log10(num));
    return 0;
}

/* - rand <int> */
private int
zrand(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;

	/*
	 * 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 */
    zrand_state = A * (zrand_state % Q) - R * (zrand_state / Q);
    /* Note that zrand_state cannot be 0 here. */
    if (zrand_state <= 0)
	zrand_state += M;
#undef A
#undef M
#undef Q
#undef R
    push(1);
    make_int(op, zrand_state);
    return 0;
}

/* <int> srand - */
private int
zsrand(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    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;
    zrand_state = state;
    pop(1);
    return 0;
}

/* - rrand <int> */
private int
zrrand(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;

    push(1);
    make_int(op, zrand_state);
    return 0;
}

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

const 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(0)
};
