288 lines
6.7 KiB
C
288 lines
6.7 KiB
C
/*
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* $Id: eval.c,v 1.13 2005-09-24 08:16:02 bacon Exp $
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*/
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#include <xp/lsp/lsp.h>
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#include <xp/lsp/env.h>
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#include <xp/lsp/prim.h>
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#include <xp/bas/assert.h>
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static xp_lsp_obj_t* make_func (
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xp_lsp_t* lsp, xp_lsp_obj_t* cdr, int is_macro);
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static xp_lsp_obj_t* eval_cons (
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xp_lsp_t* lsp, xp_lsp_obj_t* cons);
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static xp_lsp_obj_t* apply (
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xp_lsp_t* lsp, xp_lsp_obj_t* func, xp_lsp_obj_t* actual);
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xp_lsp_obj_t* xp_lsp_eval (xp_lsp_t* lsp, xp_lsp_obj_t* obj)
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{
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lsp->errnum = XP_LSP_ERR_NONE;
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if (XP_LSP_TYPE(obj) == XP_LSP_OBJ_CONS)
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return eval_cons (lsp, obj);
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else if (XP_LSP_TYPE(obj) == XP_LSP_OBJ_SYMBOL) {
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xp_lsp_assoc_t* assoc;
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/*
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if (obj == lsp->mem->lambda || obj == lsp->mem->macro) {
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printf ("lambda or macro can't be used as a normal symbol\n");
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lsp->errnum = XP_LSP_ERR_BAD_SYMBOL;
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return XP_NULL;
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}
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*/
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assoc = xp_lsp_lookup(lsp->mem, obj);
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if (assoc == XP_NULL || assoc->value == XP_NULL) {
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if (lsp->opt_undef_symbol) {
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lsp->errnum = XP_LSP_ERR_UNDEF_SYMBOL;
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return XP_NULL;
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}
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return lsp->mem->nil;
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}
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obj = assoc->value;
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}
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return obj;
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}
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static xp_lsp_obj_t* make_func (xp_lsp_t* lsp, xp_lsp_obj_t* cdr, int is_macro)
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{
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xp_lsp_obj_t* func, * formal, * body, * p;
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if (cdr == lsp->mem->nil) {
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lsp->errnum = XP_LSP_ERR_TOO_FEW_ARGS;
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return XP_NULL;
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}
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if (XP_LSP_TYPE(cdr) != XP_LSP_OBJ_CONS) {
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lsp->errnum = XP_LSP_ERR_BAD_ARG;
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return XP_NULL;
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}
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formal = XP_LSP_CAR(cdr);
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body = XP_LSP_CDR(cdr);
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if (body == lsp->mem->nil) {
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lsp->errnum = XP_LSP_ERR_EMPTY_BODY;
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return XP_NULL;
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}
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// TODO: more lambda expression syntax checks required???.
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/* check if the lambda express has non-nil value
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* at the terminating cdr */
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for (p = body; XP_LSP_TYPE(p) == XP_LSP_OBJ_CONS; p = XP_LSP_CDR(p));
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if (p != lsp->mem->nil) {
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/* like in (lambda (x) (+ x 10) . 4) */
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lsp->errnum = XP_LSP_ERR_BAD_ARG;
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return XP_NULL;
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}
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func = (is_macro)?
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xp_lsp_make_macro (lsp->mem, formal, body):
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xp_lsp_make_func (lsp->mem, formal, body);
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if (func == XP_NULL) {
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lsp->errnum = XP_LSP_ERR_MEMORY;
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return XP_NULL;
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}
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return func;
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}
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static xp_lsp_obj_t* eval_cons (xp_lsp_t* lsp, xp_lsp_obj_t* cons)
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{
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xp_lsp_obj_t* car, * cdr;
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xp_assert (XP_LSP_TYPE(cons) == XP_LSP_OBJ_CONS);
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car = XP_LSP_CAR(cons);
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cdr = XP_LSP_CDR(cons);
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if (car == lsp->mem->lambda) {
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return make_func (lsp, cdr, 0);
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}
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else if (car == lsp->mem->macro) {
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return make_func (lsp, cdr, 1);
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}
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else if (XP_LSP_TYPE(car) == XP_LSP_OBJ_SYMBOL) {
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xp_lsp_assoc_t* assoc;
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if ((assoc = xp_lsp_lookup(lsp->mem, car)) != XP_NULL) {
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//xp_lsp_obj_t* func = assoc->value;
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xp_lsp_obj_t* func = assoc->func;
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if (func == XP_NULL) {
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/* the symbol's function definition is void */
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lsp->errnum = XP_LSP_ERR_UNDEF_FUNC;
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return XP_NULL;
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}
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if (XP_LSP_TYPE(func) == XP_LSP_OBJ_FUNC ||
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XP_LSP_TYPE(func) == XP_LSP_OBJ_MACRO) {
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return apply (lsp, func, cdr);
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}
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else if (XP_LSP_TYPE(func) == XP_LSP_OBJ_PRIM) {
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/* primitive function */
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return XP_LSP_PRIM(func) (lsp, cdr);
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}
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else {
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//TODO: emit the name for debugging
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lsp->errnum = XP_LSP_ERR_UNDEF_FUNC;
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return XP_NULL;
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}
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}
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else {
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//TODO: better error handling.
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//TODO: emit the name for debugging
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lsp->errnum = XP_LSP_ERR_UNDEF_FUNC;
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return XP_NULL;
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}
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}
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else if (XP_LSP_TYPE(car) == XP_LSP_OBJ_FUNC ||
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XP_LSP_TYPE(car) == XP_LSP_OBJ_MACRO) {
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return apply (lsp, car, cdr);
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}
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else if (XP_LSP_TYPE(car) == XP_LSP_OBJ_CONS) {
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if (XP_LSP_CAR(car) == lsp->mem->lambda) {
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xp_lsp_obj_t* func = make_func (lsp, XP_LSP_CDR(car), 0);
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if (func == XP_NULL) return XP_NULL;
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return apply (lsp, func, cdr);
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}
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else if (XP_LSP_CAR(car) == lsp->mem->macro) {
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xp_lsp_obj_t* func = make_func (lsp, XP_LSP_CDR(car), 1);
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if (func == XP_NULL) return XP_NULL;
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return apply (lsp, func, cdr);
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}
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}
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//TODO: emit the name for debugging
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lsp->errnum = XP_LSP_ERR_BAD_FUNC;
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return XP_NULL;
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}
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static xp_lsp_obj_t* apply (
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xp_lsp_t* lsp, xp_lsp_obj_t* func, xp_lsp_obj_t* actual)
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{
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xp_lsp_frame_t* frame;
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xp_lsp_obj_t* formal;
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xp_lsp_obj_t* body;
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xp_lsp_obj_t* value;
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xp_lsp_mem_t* mem;
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xp_assert (
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XP_LSP_TYPE(func) == XP_LSP_OBJ_FUNC ||
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XP_LSP_TYPE(func) == XP_LSP_OBJ_MACRO);
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xp_assert (XP_LSP_TYPE(XP_LSP_CDR(func)) == XP_LSP_OBJ_CONS);
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mem = lsp->mem;
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if (XP_LSP_TYPE(func) == XP_LSP_OBJ_MACRO) {
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formal = XP_LSP_MFORMAL (func);
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body = XP_LSP_MBODY (func);
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}
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else {
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formal = XP_LSP_FFORMAL (func);
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body = XP_LSP_FBODY (func);
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}
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// make a new frame.
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frame = xp_lsp_frame_new ();
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if (frame == XP_NULL) {
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lsp->errnum = XP_LSP_ERR_MEMORY;
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return XP_NULL;
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}
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// attach it to the brooding frame list to
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// make them not to be garbage collected.
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frame->link = mem->brooding_frame;
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mem->brooding_frame = frame;
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// evaluate arguments and push them into the frame.
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while (formal != mem->nil) {
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if (actual == mem->nil) {
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lsp->errnum = XP_LSP_ERR_TOO_FEW_ARGS;
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mem->brooding_frame = frame->link;
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xp_lsp_frame_free (frame);
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return XP_NULL;
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}
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value = XP_LSP_CAR(actual);
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if (XP_LSP_TYPE(func) != XP_LSP_OBJ_MACRO) {
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// macro doesn't evaluate actual arguments.
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value = xp_lsp_eval (lsp, value);
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if (value == XP_NULL) {
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mem->brooding_frame = frame->link;
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xp_lsp_frame_free (frame);
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return XP_NULL;
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}
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}
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if (xp_lsp_frame_lookup (
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frame, XP_LSP_CAR(formal)) != XP_NULL) {
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lsp->errnum = XP_LSP_ERR_DUP_FORMAL;
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mem->brooding_frame = frame->link;
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xp_lsp_frame_free (frame);
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return XP_NULL;
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}
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if (xp_lsp_frame_insert_value (
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frame, XP_LSP_CAR(formal), value) == XP_NULL) {
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lsp->errnum = XP_LSP_ERR_MEMORY;
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mem->brooding_frame = frame->link;
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xp_lsp_frame_free (frame);
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return XP_NULL;
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}
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actual = XP_LSP_CDR(actual);
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formal = XP_LSP_CDR(formal);
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}
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if (XP_LSP_TYPE(actual) == XP_LSP_OBJ_CONS) {
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lsp->errnum = XP_LSP_ERR_TOO_MANY_ARGS;
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mem->brooding_frame = frame->link;
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xp_lsp_frame_free (frame);
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return XP_NULL;
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}
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else if (actual != mem->nil) {
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lsp->errnum = XP_LSP_ERR_BAD_ARG;
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mem->brooding_frame = frame->link;
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xp_lsp_frame_free (frame);
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return XP_NULL;
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}
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// push the frame
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mem->brooding_frame = frame->link;
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frame->link = mem->frame;
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mem->frame = frame;
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// do the evaluation of the body
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value = mem->nil;
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while (body != mem->nil) {
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value = xp_lsp_eval(lsp, XP_LSP_CAR(body));
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if (value == XP_NULL) {
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mem->frame = frame->link;
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xp_lsp_frame_free (frame);
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return XP_NULL;
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}
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body = XP_LSP_CDR(body);
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}
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// pop the frame.
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mem->frame = frame->link;
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// destroy the frame.
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xp_lsp_frame_free (frame);
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//if (XP_LSP_CAR(func) == mem->macro) {
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if (XP_LSP_TYPE(func) == XP_LSP_OBJ_MACRO) {
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value = xp_lsp_eval(lsp, value);
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if (value == XP_NULL) return XP_NULL;
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}
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return value;
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}
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