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More LL(k) fixes (Merge branch 'LL' of https://github.com/pesco/hammer)

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This commit is contained in:
Meredith L. Patterson 2013-05-24 06:11:44 -07:00
commit c8dba54bb4
4 changed files with 90 additions and 61 deletions
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74
src/backends/llk.c
View file

@ -81,28 +81,6 @@ void h_llktable_free(HLLkTable *table)
h_free(table);
}
/* Compute the predict_k set of production "A -> rhs".
* Always returns a newly-allocated HCFStringMap.
*/
HCFStringMap *h_predict(size_t k, HCFGrammar *g,
const HCFChoice *A, const HCFSequence *rhs)
{
assert(k==1); // XXX
HCFStringMap *ret = h_stringmap_new(g->arena);
// predict(A -> rhs) = first(rhs) u follow(A) if "" can be derived from rhs
// predict(A -> rhs) = first(rhs) otherwise
h_stringmap_update(ret, h_first_seq(k, g, rhs->items));
if(h_derives_epsilon_seq(g, rhs->items))
h_stringmap_update(ret, h_follow(k, g, A));
// make sure there are only strings of length _exactly_ k
ret->epsilon_branch = NULL;
return ret;
}
void *const CONFLICT = (void *)(uintptr_t)(-1);
// helper for stringmap_merge
@ -113,7 +91,7 @@ static void *combine_entries(HHashSet *workset, void *dst, const void *src)
if(dst == CONFLICT) { // previous conflict
h_hashset_put(workset, src);
} else if(dst == src) { // new conflict
} else if(dst != src) { // new conflict
h_hashset_put(workset, dst);
h_hashset_put(workset, src);
dst = CONFLICT;
@ -133,6 +111,12 @@ static void stringmap_merge(HHashSet *workset, HCFStringMap *dst, HCFStringMap *
combine_entries(workset, dst->epsilon_branch, src->epsilon_branch);
else
dst->epsilon_branch = src->epsilon_branch;
} else {
// if there is a non-conflicting value on the left (dst) side, it means
// that prediction is already unambiguous. we can drop the right (src)
// side we were going to extend with.
if(dst->epsilon_branch && dst->epsilon_branch != CONFLICT)
return;
}
if(src->end_branch) {
@ -164,9 +148,6 @@ static void stringmap_merge(HHashSet *workset, HCFStringMap *dst, HCFStringMap *
}
}
void pprint_sequence(FILE *f, const HCFGrammar *g, const HCFSequence *seq);
void pprint_symbol(FILE *f, const HCFGrammar *g, const HCFChoice *x);
/* Generate entries for the production "A" in the given table row. */
static int fill_table_row(size_t kmax, HCFGrammar *g, HCFStringMap *row,
const HCFChoice *A)
@ -181,6 +162,8 @@ static int fill_table_row(size_t kmax, HCFGrammar *g, HCFStringMap *row,
// run until workset exhausted or kmax hit
size_t k;
for(k=1; k<=kmax; k++) {
printf("k=%lu\n", k); // XXX debug
// allocate a fresh workset for the next round
HHashSet *nextset = h_hashset_new(g->arena, h_eq_ptr, h_hash_ptr);
@ -199,29 +182,30 @@ static int fill_table_row(size_t kmax, HCFGrammar *g, HCFStringMap *row,
HCFStringMap *pred = h_predict(k, g, A, rhs);
h_stringmap_replace(pred, NULL, rhs);
// XXX debug
printf("predict(");
h_pprint_sequence(stdout, g, rhs);
printf(") = ");
h_pprint_stringset(stdout, pred, 0);
// merge predict set into the row
// accumulates conflicts in new workset
stringmap_merge(nextset, row, pred);
// XXX debug
if(A == g->start) {
printf("predict(");
pprint_sequence(stdout, g, rhs);
printf(" ) = ");
h_pprint_stringset(stdout, g, pred, 0);
}
}
}
// XXX debug
if(A == g->start) {
printf("row(");
pprint_symbol(stdout, g, A);
h_pprint_symbol(stdout, g, A);
printf(") = ");
h_pprint_stringset(stdout, g, row, 0);
h_pprint_stringset(stdout, row, 0);
if(h_stringmap_get(row, (uint8_t *)"a", 1, false)) {
printf(" a -> ");
h_pprint_sequence(stdout, g, h_stringmap_get(row, (uint8_t *)"a", 1, false));
printf("\n");
}
// switch to the updated workset
h_hashtable_free(workset);
h_hashset_free(workset);
workset = nextset;
// if the workset is empty, row is without conflict; we're done
@ -473,9 +457,9 @@ int test_llk(void)
*/
HParser *X = h_optional(h_ch('x'));
HParser *Y = h_sequence(h_ch('y'), NULL);
HParser *A = h_sequence(X, Y, h_ch('a'), NULL);
HParser *B = h_sequence(Y, h_ch('b'), NULL);
//HParser *Y = h_epsilon_p(); //h_sequence(h_ch('y'), NULL);
HParser *A = h_sequence(X, h_ch('a'), NULL);
HParser *B = h_sequence(h_ch('b'), NULL);
HParser *p = h_choice(A, B, NULL);
HCFGrammar *g = h_cfgrammar(&system_allocator, p);
@ -489,16 +473,16 @@ int test_llk(void)
printf("derive epsilon: ");
h_pprint_symbolset(stdout, g, g->geneps, 0);
printf("first(A) = ");
h_pprint_stringset(stdout, g, h_first(3, g, g->start), 0);
h_pprint_stringset(stdout, h_first(3, g, g->start), 0);
//printf("follow(C) = ");
//h_pprint_stringset(stdout, g, h_follow(3, g, h_desugar(&system_allocator, c)), 0);
//h_pprint_stringset(stdout, h_follow(3, g, h_desugar(&system_allocator, c)), 0);
if(h_compile(p, PB_LLk, NULL)) {
if(h_compile(p, PB_LLk, (void *)2)) {
fprintf(stderr, "does not compile\n");
return 2;
}
HParseResult *res = h_parse(p, (uint8_t *)"xa", 2);
HParseResult *res = h_parse(p, (uint8_t *)"ab", 2);
if(res)
h_pprint(stdout, res->ast, 0, 2);
else

58
src/cfgrammar.c
View file

@ -437,7 +437,23 @@ static bool any_string_shorter(size_t k, const HCFStringMap *m)
return false;
}
const HCFStringMap *h_follow(size_t k, HCFGrammar *g, const HCFChoice *x);
// helper for h_predict
static void remove_all_shorter(size_t k, HCFStringMap *m)
{
if(k==0) return;
m->epsilon_branch = NULL;
if(k==1) return;
// iterate over m->char_branches
const HHashTable *ht = m->char_branches;
for(size_t i=0; i < ht->capacity; i++) {
for(HHashTableEntry *hte = &ht->contents[i]; hte; hte = hte->next) {
if(hte->key == NULL)
continue;
remove_all_shorter(k-1, hte->value); // recursion into subtree
}
}
}
// h_follow adapted to the signature of StringSetFun
static inline const HCFStringMap *h_follow_(size_t k, HCFGrammar *g, HCFChoice **s)
@ -507,6 +523,23 @@ const HCFStringMap *h_follow(size_t k, HCFGrammar *g, const HCFChoice *x)
return ret;
}
HCFStringMap *h_predict(size_t k, HCFGrammar *g,
const HCFChoice *A, const HCFSequence *rhs)
{
HCFStringMap *ret = h_stringmap_new(g->arena);
// predict_k(A -> rhs) =
// { ab | a <- first_k(rhs), b <- follow_k(A), |ab|=k }
const HCFStringMap *first_rhs = h_first_seq(k, g, rhs->items);
stringset_extend(g, ret, k, first_rhs, h_follow_, (HCFChoice **)&A);
// make sure there are only strings of length _exactly_ k
remove_all_shorter(k, ret);
return ret;
}
// add the set { a b | a <- as, b <- f_l(S), l=k-|a| } to ret
static void stringset_extend(HCFGrammar *g, HCFStringMap *ret,
size_t k, const HCFStringMap *as,
@ -624,7 +657,7 @@ static HCFChoice **pprint_string(FILE *f, HCFChoice **x)
return x;
}
void pprint_symbol(FILE *f, const HCFGrammar *g, const HCFChoice *x)
void h_pprint_symbol(FILE *f, const HCFGrammar *g, const HCFChoice *x)
{
switch(x->type) {
case HCF_CHAR:
@ -643,31 +676,36 @@ void pprint_symbol(FILE *f, const HCFGrammar *g, const HCFChoice *x)
}
}
void pprint_sequence(FILE *f, const HCFGrammar *g, const HCFSequence *seq)
void h_pprint_sequence(FILE *f, const HCFGrammar *g, const HCFSequence *seq)
{
HCFChoice **x = seq->items;
if(*x == NULL) { // the empty sequence
fputs(" \"\"", f);
fputs("\"\"", f);
} else {
while(*x) {
fputc(' ', f); // separator
if(x != seq->items) fputc(' ', f); // internal separator
if((*x)->type == HCF_CHAR) {
// condense character strings
x = pprint_string(f, x);
} else {
pprint_symbol(f, g, *x);
h_pprint_symbol(f, g, *x);
x++;
}
}
}
}
// adds some separators expected below
static void pprint_sequence(FILE *f, const HCFGrammar *g, const HCFSequence *seq)
{
fputc(' ', f);
h_pprint_sequence(f, g, seq);
fputc('\n', f);
}
static
void pprint_ntrules(FILE *f, const HCFGrammar *g, const HCFChoice *nt,
static void pprint_ntrules(FILE *f, const HCFGrammar *g, const HCFChoice *nt,
int indent, int len)
{
int i;
@ -738,7 +776,7 @@ void h_pprint_symbolset(FILE *file, const HCFGrammar *g, const HHashSet *set, in
a = hte->key; // production's left-hand symbol
pprint_symbol(file, g, a);
h_pprint_symbol(file, g, a);
}
}
@ -801,7 +839,7 @@ pprint_stringset_elems(FILE *file, bool first, char *prefix, size_t n,
return first;
}
void h_pprint_stringset(FILE *file, const HCFGrammar *g, const HCFStringMap *set, int indent)
void h_pprint_stringset(FILE *file, const HCFStringMap *set, int indent)
{
int j;
for(j=0; j<indent; j++) fputc(' ', file);

12
src/cfgrammar.h
View file

@ -50,7 +50,7 @@ void *h_stringmap_get(const HCFStringMap *m, const uint8_t *str, size_t n, bool
bool h_stringmap_present(const HCFStringMap *m, const uint8_t *str, size_t n, bool end);
bool h_stringmap_present_epsilon(const HCFStringMap *m);
static inline void *h_stringmap_get_char(const HCFStringMap *m, const uint8_t c)
static inline HCFStringMap *h_stringmap_get_char(const HCFStringMap *m, const uint8_t c)
{ return h_hashtable_get(m->char_branches, (void *)char_key(c)); }
@ -80,8 +80,16 @@ const HCFStringMap *h_first_seq(size_t k, HCFGrammar *g, HCFChoice **s);
/* Compute follow_k set of symbol x. Memoized. */
const HCFStringMap *h_follow(size_t k, HCFGrammar *g, const HCFChoice *x);
/* Compute the predict_k set of production "A -> rhs".
* Always returns a newly-allocated HCFStringMap.
*/
HCFStringMap *h_predict(size_t k, HCFGrammar *g,
const HCFChoice *A, const HCFSequence *rhs);
/* Pretty-printers for grammars and associated data. */
void h_pprint_grammar(FILE *file, const HCFGrammar *g, int indent);
void h_pprint_sequence(FILE *f, const HCFGrammar *g, const HCFSequence *seq);
void h_pprint_symbol(FILE *f, const HCFGrammar *g, const HCFChoice *x);
void h_pprint_symbolset(FILE *file, const HCFGrammar *g, const HHashSet *set, int indent);
void h_pprint_stringset(FILE *file, const HCFGrammar *g, const HCFStringMap *set, int indent);
void h_pprint_stringset(FILE *file, const HCFStringMap *set, int indent);

1
src/parsers/optional.c
View file

@ -25,7 +25,6 @@ static bool opt_isValidCF(void *env) {
static HParsedToken* reshape_optional(const HParseResult *p) {
assert(p->ast);
assert(p->ast->token_type == TT_SEQUENCE);
assert(p->ast->seq->used > 0);
HParsedToken *res = p->ast->seq->elements[0];
if(res)