// what is exact? it seems to only add sets from above on stack
// if EOR is in set i. When it sees a set w/o EOR, it stops adding.
// Why would we ever want them all? Maybe no viable alt instead of
// mismatched token?
protected virtual BitSet CombineFollows(bool exact)
{
int top = state._fsp;
BitSet followSet = new BitSet();
for ( int i = top; i >= 0; i-- )
{
BitSet localFollowSet = (BitSet)state.following[i];
/*
System.out.println("local follow depth "+i+"="+
localFollowSet.toString(getTokenNames())+")");
*/
followSet.OrInPlace( localFollowSet );
if ( exact )
{
// can we see end of rule?
if ( localFollowSet.Member( TokenTypes.EndOfRule ) )
{
// Only leave EOR in set if at top (start rule); this lets
// us know if have to include follow(start rule); i.e., EOF
if ( i > 0 )
{
followSet.Remove( TokenTypes.EndOfRule );
}
}
else
{ // can't see end of rule, quit
break;
}
}
}
return followSet;
}
public virtual bool MismatchIsMissingToken( IIntStream input, BitSet follow )
{
if ( follow == null )
{
// we have no information about the follow; we can only consume
// a single token and hope for the best
return false;
}
// compute what can follow this grammar element reference
if ( follow.Member( TokenTypes.EndOfRule ) )
{
BitSet viableTokensFollowingThisRule = ComputeContextSensitiveRuleFOLLOW();
follow = follow.Or( viableTokensFollowingThisRule );
if ( state._fsp >= 0 )
{ // remove EOR if we're not the start symbol
follow.Remove( TokenTypes.EndOfRule );
}
}
// if current token is consistent with what could come after set
// then we know we're missing a token; error recovery is free to
// "insert" the missing token
//System.out.println("viable tokens="+follow.toString(getTokenNames()));
//System.out.println("LT(1)="+((TokenStream)input).LT(1));
// BitSet cannot handle negative numbers like -1 (EOF) so I leave EOR
// in follow set to indicate that the fall of the start symbol is
// in the set (EOF can follow).
if ( follow.Member( input.LA( 1 ) ) || follow.Member( TokenTypes.EndOfRule ) )
{
//System.out.println("LT(1)=="+((TokenStream)input).LT(1)+" is consistent with what follows; inserting...");
return true;
}
return false;
}
