//分析 expr
ast_tree *parser_expr(token_result *result)
{
ast_tree *tree;
token *t;
if((t = next_token(result)) == NULL)
return NULL;
if(t->type == TOKEN_NUM){
tree = new_tree();
ast_tag(tree,"expr");
return parser_num(tree, t->num);
}
if(t->type == TOKEN_SYM){
if(strcmp(t->sym, "(") == 0){
putback_token();
return parser_sexpr(result);
}
if(strcmp(t->sym, "'") == 0){
putback_token();
return parser_qexpr(result);
}
else{
tree = new_tree();
ast_tag(tree,"expr");
return parser_sym(tree, t->sym);
}
}
}
// 分析 qexpr
ast_tree *parser_qexpr(token_result *result)
{
token *t;
ast_tree *tree = new_tree(), *temp;
ast_tag(tree, "qexpr");
//读取引号
t = next_token(result);
ast_tree_add(tree, parser_char(t->sym));
//检查是否为Q_EXPR
t = next_token(result);
if( t->type != TOKEN_SYM || strcmp(t->sym, "(") != 0)
return parser_err("QEXPRSSION miss left brace");
else
ast_tree_add(tree, parser_char(t->sym));
while((t = next_token(result))){
if(t->type == TOKEN_SYM && strcmp(t->sym, ")") == 0){
ast_tree_add(tree, parser_char(t->sym));
return tree;
}
putback_token();
temp = parser_expr(result);
if(strstr(temp->tag, "error"))
return temp;
ast_tree_add(tree, temp);
}
return parser_err("miss the back quote!");
}
/* Read a list. The opening '(' has already been read when this is called. */
static sexpr *readlist(IC *ic) {
char *token = gettoken(ic->r);
if(token == NULL) return ic->eof;
if(!strcmp(token, ")")) return ic->g_nil;
if(!strcmp(token, ".")) {
sexpr *tmp = readobj(ic);
token = gettoken(ic->r);
if(token == NULL) return ic->eof;
if(strcmp(token, ")")) return ic->g_nil;
return tmp;
}
putback_token(ic->r, token);
sexpr *first = readobj(ic); /* Must force evaluation order */
protect_ptr(ic->g, (void **) &first);
sexpr *rest = readlist(ic);
protect_ptr(ic->g, (void **) &rest);
sexpr *ret = cons(ic, first, rest);
unprotect_ptr(ic->g);
unprotect_ptr(ic->g);
return ret;
}
//分析 sexpr
ast_tree *parser_sexpr(token_result *result)
{
token *t;
ast_tree *tree = new_tree(), *temp;
ast_tag(tree, "sexpr");
//读取前括号
t = next_token(result);
ast_tree_add(tree, parser_char(t->sym));
while((t = next_token(result))){
if(t->type == TOKEN_SYM && strcmp(t->sym, ")") == 0){
ast_tree_add(tree, parser_char(t->sym));
return tree;
}
putback_token();
temp = parser_expr(result);
//出错则直接返回
if(strstr(temp->tag, "error"))
return temp;
ast_tree_add(tree, temp);
}
return parser_err("miss the back quote!");
}
