305 lines
6.9 KiB
C
305 lines
6.9 KiB
C
/*
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* $Id: eval.c,v 1.18 2006-10-26 09:31:28 bacon Exp $
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*/
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#include <ase/lsp/lsp_i.h>
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static ase_lsp_obj_t* make_func (
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ase_lsp_t* lsp, ase_lsp_obj_t* cdr, int is_macro);
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static ase_lsp_obj_t* eval_cons (
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ase_lsp_t* lsp, ase_lsp_obj_t* cons);
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static ase_lsp_obj_t* apply (
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ase_lsp_t* lsp, ase_lsp_obj_t* func, ase_lsp_obj_t* actual);
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ase_lsp_obj_t* ase_lsp_eval (ase_lsp_t* lsp, ase_lsp_obj_t* obj)
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{
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lsp->errnum = ASE_LSP_ENOERR;
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if (ASE_LSP_TYPE(obj) == ASE_LSP_OBJ_CONS)
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return eval_cons (lsp, obj);
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else if (ASE_LSP_TYPE(obj) == ASE_LSP_OBJ_SYM) {
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ase_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 = ASE_LSP_ERR_BAD_SYMBOL;
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return ASE_NULL;
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}
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*/
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assoc = ase_lsp_lookup(lsp->mem, obj);
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if (assoc == ASE_NULL || assoc->value == ASE_NULL) {
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if (lsp->opt_undef_symbol) {
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lsp->errnum = ASE_LSP_ERR_UNDEF_SYMBOL;
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return ASE_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 ase_lsp_obj_t* make_func (ase_lsp_t* lsp, ase_lsp_obj_t* cdr, int is_macro)
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{
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ase_lsp_obj_t* func, * formal, * body, * p;
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if (cdr == lsp->mem->nil) {
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lsp->errnum = ASE_LSP_ERR_TOO_FEW_ARGS;
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return ASE_NULL;
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}
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if (ASE_LSP_TYPE(cdr) != ASE_LSP_OBJ_CONS) {
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lsp->errnum = ASE_LSP_ERR_BAD_ARG;
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return ASE_NULL;
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}
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formal = ASE_LSP_CAR(cdr);
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body = ASE_LSP_CDR(cdr);
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if (body == lsp->mem->nil) {
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lsp->errnum = ASE_LSP_ERR_EMPTY_BODY;
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return ASE_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; ASE_LSP_TYPE(p) == ASE_LSP_OBJ_CONS; p = ASE_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 = ASE_LSP_ERR_BAD_ARG;
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return ASE_NULL;
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}
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func = (is_macro)?
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ase_lsp_makemacro (lsp->mem, formal, body):
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ase_lsp_makefunc (lsp->mem, formal, body);
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if (func == ASE_NULL) {
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lsp->errnum = ASE_LSP_ENOMEM;
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return ASE_NULL;
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}
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return func;
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}
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static ase_lsp_obj_t* eval_cons (ase_lsp_t* lsp, ase_lsp_obj_t* cons)
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{
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ase_lsp_obj_t* car, * cdr;
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ASE_LSP_ASSERT (lsp, ASE_LSP_TYPE(cons) == ASE_LSP_OBJ_CONS);
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car = ASE_LSP_CAR(cons);
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cdr = ASE_LSP_CDR(cons);
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if (car == lsp->mem->lambda)
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{
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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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{
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return make_func (lsp, cdr, 1);
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}
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else if (ASE_LSP_TYPE(car) == ASE_LSP_OBJ_SYM)
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{
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ase_lsp_assoc_t* assoc;
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if ((assoc = ase_lsp_lookup(lsp->mem, car)) != ASE_NULL)
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{
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//ase_lsp_obj_t* func = assoc->value;
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ase_lsp_obj_t* func = assoc->func;
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if (func == ASE_NULL) {
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/* the symbol's function definition is void */
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lsp->errnum = ASE_LSP_ERR_UNDEF_FUNC;
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return ASE_NULL;
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}
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if (ASE_LSP_TYPE(func) == ASE_LSP_OBJ_FUNC ||
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ASE_LSP_TYPE(func) == ASE_LSP_OBJ_MACRO)
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{
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return apply (lsp, func, cdr);
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}
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else if (ASE_LSP_TYPE(func) == ASE_LSP_OBJ_PRIM)
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{
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/* primitive function */
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return ASE_LSP_PRIM(func) (lsp, cdr);
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}
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else
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{
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//TODO: emit the name for debugging
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lsp->errnum = ASE_LSP_ERR_UNDEF_FUNC;
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return ASE_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 = ASE_LSP_ERR_UNDEF_FUNC;
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return ASE_NULL;
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}
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}
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else if (ASE_LSP_TYPE(car) == ASE_LSP_OBJ_FUNC ||
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ASE_LSP_TYPE(car) == ASE_LSP_OBJ_MACRO) {
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return apply (lsp, car, cdr);
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}
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else if (ASE_LSP_TYPE(car) == ASE_LSP_OBJ_CONS) {
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if (ASE_LSP_CAR(car) == lsp->mem->lambda) {
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ase_lsp_obj_t* func = make_func (lsp, ASE_LSP_CDR(car), 0);
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if (func == ASE_NULL) return ASE_NULL;
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return apply (lsp, func, cdr);
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}
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else if (ASE_LSP_CAR(car) == lsp->mem->macro) {
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ase_lsp_obj_t* func = make_func (lsp, ASE_LSP_CDR(car), 1);
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if (func == ASE_NULL) return ASE_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 = ASE_LSP_ERR_BAD_FUNC;
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return ASE_NULL;
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}
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static ase_lsp_obj_t* apply (
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ase_lsp_t* lsp, ase_lsp_obj_t* func, ase_lsp_obj_t* actual)
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{
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ase_lsp_frame_t* frame;
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ase_lsp_obj_t* formal;
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ase_lsp_obj_t* body;
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ase_lsp_obj_t* value;
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ase_lsp_mem_t* mem;
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ASE_LSP_ASSERT (lsp,
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ASE_LSP_TYPE(func) == ASE_LSP_OBJ_FUNC ||
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ASE_LSP_TYPE(func) == ASE_LSP_OBJ_MACRO);
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ASE_LSP_ASSERT (lsp,
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ASE_LSP_TYPE(ASE_LSP_CDR(func)) == ASE_LSP_OBJ_CONS);
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mem = lsp->mem;
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if (ASE_LSP_TYPE(func) == ASE_LSP_OBJ_MACRO)
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{
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formal = ASE_LSP_MFORMAL (func);
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body = ASE_LSP_MBODY (func);
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}
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else
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{
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formal = ASE_LSP_FFORMAL (func);
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body = ASE_LSP_FBODY (func);
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}
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/* make a new frame. */
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frame = ase_lsp_newframe (lsp);
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if (frame == ASE_NULL)
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{
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lsp->errnum = ASE_LSP_ENOMEM;
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return ASE_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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{
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if (actual == mem->nil)
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{
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lsp->errnum = ASE_LSP_ERR_TOO_FEW_ARGS;
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mem->brooding_frame = frame->link;
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ase_lsp_freeframe (lsp, frame);
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return ASE_NULL;
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}
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value = ASE_LSP_CAR(actual);
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if (ASE_LSP_TYPE(func) != ASE_LSP_OBJ_MACRO)
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{
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// macro doesn't evaluate actual arguments.
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value = ase_lsp_eval (lsp, value);
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if (value == ASE_NULL)
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{
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mem->brooding_frame = frame->link;
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ase_lsp_freeframe (lsp, frame);
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return ASE_NULL;
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}
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}
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if (ase_lsp_lookupinframe (
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lsp, frame, ASE_LSP_CAR(formal)) != ASE_NULL)
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{
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lsp->errnum = ASE_LSP_ERR_DUP_FORMAL;
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mem->brooding_frame = frame->link;
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ase_lsp_freeframe (lsp, frame);
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return ASE_NULL;
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}
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if (ase_lsp_insertvalueintoframe (
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lsp, frame, ASE_LSP_CAR(formal), value) == ASE_NULL)
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{
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lsp->errnum = ASE_LSP_ENOMEM;
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mem->brooding_frame = frame->link;
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ase_lsp_freeframe (lsp, frame);
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return ASE_NULL;
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}
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actual = ASE_LSP_CDR(actual);
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formal = ASE_LSP_CDR(formal);
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}
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if (ASE_LSP_TYPE(actual) == ASE_LSP_OBJ_CONS)
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{
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lsp->errnum = ASE_LSP_ERR_TOO_MANY_ARGS;
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mem->brooding_frame = frame->link;
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ase_lsp_freeframe (lsp, frame);
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return ASE_NULL;
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}
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else if (actual != mem->nil)
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{
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lsp->errnum = ASE_LSP_ERR_BAD_ARG;
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mem->brooding_frame = frame->link;
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ase_lsp_freeframe (lsp, frame);
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return ASE_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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{
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value = ase_lsp_eval(lsp, ASE_LSP_CAR(body));
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if (value == ASE_NULL)
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{
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mem->frame = frame->link;
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ase_lsp_freeframe (lsp, frame);
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return ASE_NULL;
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}
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body = ASE_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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ase_lsp_freeframe (lsp, frame);
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//if (ASE_LSP_CAR(func) == mem->macro) {
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if (ASE_LSP_TYPE(func) == ASE_LSP_OBJ_MACRO)
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{
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value = ase_lsp_eval(lsp, value);
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if (value == ASE_NULL) return ASE_NULL;
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}
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return value;
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}
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