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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifndef XCALLOC_IMPLEMENTED
#define XCALLOC_IMPLEMENTED
void *xcalloc(size_t n, size_t size) { void *addr = calloc(n, size); return addr ? addr : (exit(1), NULL); }
#else
extern void *xcalloc(size_t n, size_t size);
#endif
typedef unsigned int symbol;
extern const size_t total_symbols;
extern struct production {
symbol LHS;
symbol *RHS;
size_t nRHS;
} grammar[];
extern const size_t total_productions;
int **follow;
int **first;
// int *nullable;
void util_tables_fill()
{
follow = calloc(total_symbols, sizeof(*follow));
first = calloc(total_symbols, sizeof(*follow));
for(size_t i = 0; i < total_symbols; i++) {
follow[i] = xcalloc(total_symbols, sizeof(*follow[i]));
first[i] = xcalloc(total_symbols, sizeof(*follow[i]));
}
for(size_t sym = 0; sym < total_symbols; sym++) {
first[sym][sym] = 1;
}
for(size_t i = 0; i < total_productions; i++) {
struct production *p = &grammar[i];
first[p->LHS][p->RHS[0]] = 1;
for(size_t j = 1; j < p->nRHS; j++)
follow[p->RHS[j-1]][p->RHS[j]] = 1;
}
#define set(e) if((e) != 1) changed = (e) = 1
int changed;
do {
changed = 0;
for(size_t i = 0; i < total_productions; i++)
for(size_t sym = 0; sym < total_symbols; sym++) {
struct production *p = &grammar[i];
if(first[sym][p->LHS])
for(size_t j = 0; j < total_symbols; j++)
if(first[p->LHS][j]) set(first[sym][j]);
if(follow[p->LHS][sym])
set(follow[p->RHS[p->nRHS-1]][sym]);
if(follow[sym][p->LHS])
set(follow[sym][p->RHS[0]]);
}
} while(changed);
}
void util_tables_free()
{
for(size_t i = 0; i < total_symbols; i++) {
free(follow[i]);
free(first[i]);
}
free(follow);
free(first);
}
void util_tables_print()
{
char *s1 = "-- FIRST --";
printf(" %*s%s\n", (int)((total_symbols*3) - strlen(s1))/2, "", s1);
printf(" ");
for(size_t i = 0; i < total_symbols; i++) printf("%2zu ", i);
printf("\n");
for(size_t i = 0; i < total_symbols; i++) {
printf("%2zu ", i);
for(size_t j = 0; j < total_symbols; j++)
printf(" %s ", first[i][j] ? "x" : " ");
printf("\n");
}
printf("\n");
char *s2 = "-- FOLLOW --";
printf(" %*s%s\n", (int)((total_symbols*3) - strlen(s2))/2, "", s2);
printf(" ");
for(size_t i = 0; i < total_symbols; i++) printf("%2zu ", i);
printf("\n");
for(size_t i = 0; i < total_symbols; i++) {
printf("%2zu ", i);
for(size_t j = 0; j < total_symbols; j++)
printf(" %s ", follow[i][j] ? "x" : " ");
printf("\n");
}
}
#ifdef _UTIL_TABLES_STANDALONE
enum symbol {
PLUS = 0,
MINUS,
LPAREN,
RPAREN,
N0, N1,
END_INPUT,
EP, E, T, N,
SYMBOLS_END,
};
const size_t total_symbols = SYMBOLS_END;
int symbol_is_terminal(symbol s) { return s < E; }
int symbol_is_nonterminal(symbol s) { return s >= E; }
int symbol_is_input_end(symbol s) { return s == END_INPUT; }
#define PROD(LHS, _, ...) {LHS, (symbol[]){__VA_ARGS__}, sizeof((symbol[]){__VA_ARGS__})/sizeof(symbol)}
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),
};
const size_t total_productions = sizeof(grammar)/sizeof(*grammar);
int main(void)
{
util_tables_fill();
util_tables_print();
util_tables_free();
return 0;
}
#endif
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