Integer based tags to avoid so many string comparions #44
Description
Hello.
I've been exploring MPC because I needed it for a project. MPC is quite cool because It's easy to build a parser and work with it, but one thing has been bothering me.
I need to build a parser for a programming language and after that I need to do several operations over it, such as Type Analysis, its actual evaluation, or generation of some other intermediate code from the resulting AST. The thing is, to do this I need to traverse the resulting AST. This means that at each node I need to do string comparisons with the tag field of the AST.
This makes traversing the tree a slow process.
Is there any use case of MPC that allows me to traverse an AST in a faster way in which I can avoid so many string comparisons? Alternatively, do you have any plans to implement any other identification method for nodes other then string tags?
A way to make things faster would have an integer value associated with every tag. The question is, how to integrate that in MPC in a nice way? How about something like this:
#include <mpc.h>
typedef enum {
tag_int,
tag_expr_mul,
tag_expr_add,
tag_input
} MyTags;
int main() {
mpc_parser_t *mpc_int = mpc_new("int", tag_int);
mpc_parser_t *mpc_expr_mul = mpc_new("expr_mul", tag_expr_mult);
mpc_parser_t *mpc_expr_add = mpc_new("expr_add", tag_expr_add);
mpc_parser_t *mpc_input = mpc_new("input", tag_input);
/* ... */
return 0;
}This doesn't look as nice as the current implementation, but while traversing the tree we can have comparisons like:
int traverse(mpc_ast_t *ast) {
if(ast->tag_i == tag_expr_add) {
return traverse(ast->children[L_OPR]) + traverse(ast->children[R_OPR]);
}
/* ... */
}What are your thoughts on this?
Regards!
(Notice that the example I've provided is just a quick and dirty example I made using MPC to build a simple integer calculator)