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Fix a bug in lemon in computation of which non-terminals can generate an

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empty string.  This bug and the fix make absolutely no difference for the
grammar used by SQLite, but it can make a difference when lemon is used
in other grammars.

FossilOrigin-Name: ce32775b232da894343f62deefaf19b0ec484636
This commit is contained in:
drh
2012-01-07 15:17:18 +00:00
parent 60e4a74879
commit 7dd1ac600e
3 changed files with 10 additions and 9 deletions
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5
tool/lemon.c
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@ -686,8 +686,9 @@ void FindFirstSets(struct lemon *lemp)
for(rp=lemp->rule; rp; rp=rp->next){
if( rp->lhs->lambda ) continue;
for(i=0; i<rp->nrhs; i++){
struct symbol *sp = rp->rhs[i];
if( sp->type!=TERMINAL || sp->lambda==LEMON_FALSE ) break;
struct symbol *sp = rp->rhs[i];
assert( sp->type==NONTERMINAL || sp->lambda==LEMON_FALSE );
if( sp->lambda==LEMON_FALSE ) break;
}
if( i==rp->nrhs ){
rp->lhs->lambda = LEMON_TRUE;