public virtual SemanticContext GetGatedPredicatesInNFAConfigurations()
{
SemanticContext unionOfPredicatesFromAllAlts = null;
int numConfigs = _nfaConfigurations.Count;
for ( int i = 0; i < numConfigs; i++ )
{
NFAConfiguration configuration = (NFAConfiguration)_nfaConfigurations[i];
SemanticContext gatedPredExpr =
configuration.SemanticContext.GatedPredicateContext;
if ( gatedPredExpr == null )
{
// if we ever find a configuration w/o a gated predicate
// (even if it's a nongated predicate), we cannot gate
// the indident edges.
return null;
}
else if ( IsAcceptState || !configuration.SemanticContext.IsSyntacticPredicate )
{
// at this point we have a gated predicate and, due to elseif,
// we know it's an accept or not a syn pred. In this case,
// it's safe to add the gated predicate to the union. We
// only want to add syn preds if it's an accept state. Other
// gated preds can be used with edges leading to accept states.
if ( unionOfPredicatesFromAllAlts == null )
{
unionOfPredicatesFromAllAlts = gatedPredExpr;
}
else
{
unionOfPredicatesFromAllAlts =
SemanticContext.Or( unionOfPredicatesFromAllAlts, gatedPredExpr );
}
}
}
if ( unionOfPredicatesFromAllAlts is SemanticContext.TruePredicate )
{
return null;
}
return unionOfPredicatesFromAllAlts;
}
