/**
 *  payloads/special.h
 *
 *  A special form.
 *
 *  (c) 2026 Simon Brooke <simon@journeyman.cc>
 *  Licensed under GPL version 2.0, or, at your option, any later version.
 */

#ifndef __psse_payloads_special_h
#define __psse_payloads_special_h

#include "memory/pointer.h"

/**
 * A special form - one whose arguments are not pre-evaluated but passed as
 * provided.
 * \see NLAMBDATAG.
 */
#define SPECIALTAG  "SFM"

/**
 * @brief Payload of a special form cell. 
 *
 * Currently identical to the payload of a function cell.
 * \see function_payload
 */
struct special_payload {
    /**
     * pointer to the source from which the special form was compiled, or NIL
     * if it is a primitive.
     */
    struct cons_pointer meta;
    /**  pointer to a function which takes a cons pointer (representing
     * its argument list) and a cons pointer (representing its environment) and a
     * stack frame (representing the previous stack frame) as arguments and returns
     * a cons pointer (representing its result). */
    struct cons_pointer ( *executable ) ( struct stack_frame *,
                                          struct cons_pointer,
                                          struct cons_pointer );
};

#endif