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#include <stdio.h>
#include <stdlib.h>
// TODO: - check erros and fail safely and
// see connection with the lexer
// - standardize this
// Requirements
#include "parts/symbol.h"
#include "parts/grammar.h"
#include "parts/table.h"
#include "parts/toklist.h"
// and
typedef int (*semantic_action_fn)(int *stack_head);
extern semantic_action_fn *semantic_actions;
typedef int stack_item;
#define STACK_CAP 128
static stack_item stack_bottom[STACK_CAP];
static stack_item *stack_head = stack_bottom;
int lr_parser(int *value)
{
#define push(item) do { \
if(++stack_head - stack_bottom < STACK_CAP ) *stack_head = item; \
else { fprintf(stderr, "ERROR: STACK_CAP exceeded\n"); return 1; } \
} while(0)
#define pop() (--stack_head)
#define eat() toklist_eat()
#define peek() toklist_peek()
while(1) {
struct action a = table[(size_t)*stack_head][token_sym(peek())];
switch(a.type) {
case ACTION_SHIFT:;
struct token *t = eat();
push(token_sym(t));
push(token_val(t));
push(a.arg);
break;
case ACTION_REDUCE:
int semantic_value = semantic_actions[a.arg](stack_head);
for(size_t i = 0; i < 3*grammar[a.arg].nRHS; i++) pop();
symbol lhs = grammar[a.arg].LHS;
struct action a_goto = table[(size_t)*stack_head][lhs];
if(a_goto.type != ACTION_GOTO) {
fprintf(stderr,
"ERROR: Expected goto action for token '%d' at state %zu\n",
lhs, (size_t)*stack_head);
return 1;
}
push(lhs);
push(semantic_value);
push(a_goto.arg);
break;
case ACTION_ACCEPT:
*value = *(stack_head-1);
return 0;
case ACTION_NOT_SET:
default:
fprintf(stderr,
"ERROR: Unexpected symbol '%d' at state %zu\n",
token_sym(peek()), (size_t)*stack_head);
return 1;
}
}
return 1;
}
#ifdef _LR_PARSER_STANDALONE
// implement symbol.h
enum symbol {
PLUS = 0,
MINUS,
LPAREN,
RPAREN,
N0, N1,
END_INPUT,
EP, E, T, N,
SYMBOLS_END,
};
size_t total_symbols = SYMBOLS_END;
IMPLEMENT_FUNCPTR(int, symbol_is_valid, (symbol s)) { return s < SYMBOLS_END; }
// implement grammar.h
#define PROD(LHS, _, ...) {LHS, (symbol[]){__VA_ARGS__}, sizeof((symbol[]){__VA_ARGS__})/sizeof(symbol)}
static struct production _grammar[] = {
PROD(EP, ->, E, END_INPUT),
PROD(E, -->, E, PLUS, T),
PROD(E, -->, E, MINUS, T),
PROD(E, -->, T),
PROD(T, -->, LPAREN, E, RPAREN),
PROD(T, -->, N),
PROD(N, -->, N0),
PROD(N, -->, N1),
};
struct production *grammar = _grammar;
size_t total_productions = sizeof(_grammar)/sizeof(*_grammar);
// implement table.h
struct action **table = (struct action *([])){
(struct action[]){{0, 0},{0, 0},{1, 1},{0, 0},{1, 2},{1, 3},{0, 0},{0, 0},{2, 12},{2, 11},{2, 7},},
(struct action[]){{0, 0},{0, 0},{1, 1},{0, 0},{1, 2},{1, 3},{0, 0},{0, 0},{2, 4},{2, 11},{2, 7},},
(struct action[]){{3, 6},{3, 6},{0, 0},{3, 6},{0, 0},{0, 0},{3, 6},{0, 0},{0, 0},{0, 0},{0, 0},},
(struct action[]){{3, 7},{3, 7},{0, 0},{3, 7},{0, 0},{0, 0},{3, 7},{0, 0},{0, 0},{0, 0},{0, 0},},
(struct action[]){{1, 5},{1, 8},{0, 0},{1, 10},{0, 0},{0, 0},{0, 0},{0, 0},{0, 0},{0, 0},{0, 0},},
(struct action[]){{0, 0},{0, 0},{1, 1},{0, 0},{1, 2},{1, 3},{0, 0},{0, 0},{0, 0},{2, 6},{2, 7},},
(struct action[]){{3, 1},{3, 1},{0, 0},{3, 1},{0, 0},{0, 0},{3, 1},{0, 0},{0, 0},{0, 0},{0, 0},},
(struct action[]){{3, 5},{3, 5},{0, 0},{3, 5},{0, 0},{0, 0},{3, 5},{0, 0},{0, 0},{0, 0},{0, 0},},
(struct action[]){{0, 0},{0, 0},{1, 1},{0, 0},{1, 2},{1, 3},{0, 0},{0, 0},{0, 0},{2, 9},{2, 7},},
(struct action[]){{3, 2},{3, 2},{0, 0},{3, 2},{0, 0},{0, 0},{3, 2},{0, 0},{0, 0},{0, 0},{0, 0},},
(struct action[]){{3, 4},{3, 4},{0, 0},{3, 4},{0, 0},{0, 0},{3, 4},{0, 0},{0, 0},{0, 0},{0, 0},},
(struct action[]){{3, 3},{3, 3},{0, 0},{3, 3},{0, 0},{0, 0},{3, 3},{0, 0},{0, 0},{0, 0},{0, 0},},
(struct action[]){{1, 5},{1, 8},{0, 0},{0, 0},{0, 0},{0, 0},{4, 0},{0, 0},{0, 0},{0, 0},{0, 0},},
};
size_t table_states = 13;
// implement toklist.h
struct token {
symbol s;
int v;
};
static struct token toklist[] = {{N0}, {PLUS}, {N1}, {END_INPUT}};
static const size_t ntoklist = sizeof(toklist)/sizeof(*toklist);
static size_t tok;
struct token *toklist_eat()
{
if(tok == ntoklist) return toklist + ntoklist-1;
return toklist + tok++;
}
struct token *toklist_peek() { return toklist + tok; }
symbol token_sym(struct token *t) { return t->s; }
int token_val(struct token *t) { return t->v; }
int none(int *stack_head) {(void)stack_head; return 0;}
semantic_action_fn *semantic_actions = (semantic_action_fn[]){none, none, none, none, none, none, none, none};
int main(void)
{
int value;
if(lr_parser(&value)) return 1;
printf("%d\n", value);
return 0;
}
#endif
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