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#ifndef BU_PARSER_HG
#define BU_PARSER_HG
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "tree.h"
/* PRODUCTION RULES
<expr> ::= <expr> <binary_op> <expr> | <unary_op> <expr> | <var>
<binary_op> ::= "*" | "+"
<unary_op> ::= "!"
<var> ::= r#[a-z]
*/
/* POSSIBILITIES
a-z => var
*/
enum parser_state {
PARSER_ERR = -1,
PARSER_READY = 0,
PARSER_ACCEPT,
};
enum token_id {
TOKEN_INVALID = 0,
TOKEN_BINARY_OPERATOR,
TOKEN_UNARY_OPERATOR,
TOKEN_VARIABLE,
TOKEN_EOS,
TOKEN_OOB,
TOKEN_MAX,
};
enum stackmember_id {
// all token ids
STACKMEMBER_INVALID = TOKEN_INVALID,
// ...
STACKMEMBER_EXPR = TOKEN_MAX + 1,
STACKMEMBER_MAX,
};
struct chartoken { enum token_id id; char c; };
typedef struct chartoken(*lexer_fn)(void*);
struct stackmember {
enum stackmember_id id;
union {
char terminal;
node *expr;
};
};
struct expr_parser {
lexer_fn lex;
void *lex_data;
// since tokens are 1-to-1 maps to chars,
// we're fine making this type assumption
struct chartoken lahead;
enum parser_state st;
// (and 1024 oughta be enough, FIXME if not)
struct stackmember stack[1024];
size_t stack_idx;
};
struct expr_parser expr_parser_init(lexer_fn src, void* lex_data);
void expr_parser_finish(struct expr_parser *ep);
int expr_parser_run(struct expr_parser *ep);
void expr_parser_debug_print(FILE *stream, struct expr_parser *ep);
#endif // BU_PARSER_HG
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