/**
* Parses a regular expression. This method handles the Expr
* production in the grammar (see regexp.grammar).
*
* @param start the initial NFA state
*
* @return the terminating NFA state
*
* @throws RegExpException if an error was encountered in the
* pattern string
*/
private NFAState ParseExpr(NFAState start)
{
NFAState end = new NFAState();
NFAState subStart;
NFAState subEnd;
do
{
if (PeekChar(0) == '|')
{
ReadChar('|');
}
subStart = new NFAState();
subEnd = ParseTerm(subStart);
if (subStart.incoming.Length == 0)
{
subStart.MergeInto(start);
}
else
{
start.AddOut(new NFAEpsilonTransition(subStart));
}
if (subEnd.outgoing.Length == 0 ||
(!end.HasTransitions() && PeekChar(0) != '|'))
{
subEnd.MergeInto(end);
}
else
{
subEnd.AddOut(new NFAEpsilonTransition(end));
}
} while (PeekChar(0) == '|');
return(end);
}
/**
* Parses a regular expression. This method handles the Expr
* production in the grammar (see regexp.grammar).
*
* @param start the initial NFA state
*
* @return the terminating NFA state
*
* @throws RegExpException if an error was encountered in the
* pattern string
*/
private NFAState ParseExpr(NFAState start) {
NFAState end = new NFAState();
NFAState subStart;
NFAState subEnd;
do {
if (PeekChar(0) == '|') {
ReadChar('|');
}
subStart = new NFAState();
subEnd = ParseTerm(subStart);
if (subStart.incoming.Length == 0) {
subStart.MergeInto(start);
} else {
start.AddOut(new NFAEpsilonTransition(subStart));
}
if (subEnd.outgoing.Length == 0 ||
(!end.HasTransitions() && PeekChar(0) != '|')) {
subEnd.MergeInto(end);
} else {
subEnd.AddOut(new NFAEpsilonTransition(end));
}
} while (PeekChar(0) == '|');
return end;
}
