public void Action(Expansion e)
{
if (e is Sequence)
{
if (e.Parent is Choice || e.Parent is ZeroOrMore ||
e.Parent is OneOrMore || e.Parent is ZeroOrOne)
{
return;
}
Sequence seq = (Sequence)e;
Lookahead la = (Lookahead)(seq.Units[0]);
if (!la.IsExplicit)
{
return;
}
// Create a singleton choice with an empty action.
Choice ch = new Choice();
ch.Line = la.Line;
ch.Column = la.Column;
ch.Parent = seq;
Sequence seq1 = new Sequence();
seq1.Line = la.Line;
seq1.Column = la.Column;
seq1.Parent = ch;
seq1.Units.Add(la);
la.Parent = seq1;
Action act = new Action();
act.Line = la.Line;
act.Column = la.Column;
act.Parent = seq1;
seq1.Units.Add(act);
ch.Choices.Add(seq1);
if (la.Amount != 0)
{
if (la.ActionTokens.Count != 0)
{
CSharpCCErrors.Warning(la,
"Encountered LOOKAHEAD(...) at a non-choice location. " +
"Only semantic lookahead will be considered here.");
}
else
{
CSharpCCErrors.Warning(la, "Encountered LOOKAHEAD(...) at a non-choice location. This will be ignored.");
}
}
// Now we have moved the lookahead into the singleton choice. Now create
// a new dummy lookahead node to replace this one at its original location.
Lookahead la1 = new Lookahead();
la1.IsExplicit = false;
la1.Line = la.Line;
la1.Column = la.Column;
la1.Parent = seq;
// Now set the la_expansion field of la and la1 with a dummy expansion (we use EOF).
la.Expansion = new REndOfFile();
la1.Expansion = new REndOfFile();
seq.Units[0] = la1;
seq.Units[1] = ch;
}
}
private static bool explicitLA(Expansion exp)
{
if (!(exp is Sequence))
{
return(false);
}
Sequence seq = (Sequence)exp;
Object obj = seq.Units[0];
if (!(obj is Lookahead))
{
return(false);
}
Lookahead la = (Lookahead)obj;
return(la.IsExplicit);
}
public Sequence(Token token, Lookahead la)
{
Line = token.beginLine;
Column = token.beginColumn;
Units.Add(la);
}