public AlphabetBuilder(RxNode <TLetter> expression, TLetter?eof = null, RangeSet <TLetter>?validRanges = default)
{
var eofRange = eof.HasValue ? new RangeSet <TLetter>(eof.Value) : RangeSet <TLetter> .Empty;
// Step 1: Find all charset-generating regular expression parts
var visitor = new AlphabetBuilderVisitor <TLetter>();
expression.Visit(visitor, (letters, negate) => letters - eofRange);
var charsets = visitor.Charsets;
// Step 2: Get all ranges of all used charsets and register their "users"
var ranges = MakeRanges(charsets, (validRanges ?? RangeSet <TLetter> .All) - eofRange);
// Step 3: Group the information into alphabet entries
var alphabetByKey = ranges
.GroupBy <UsedLetterRange <TLetter>, string, Range <TLetter> >(r => r.GetUsersKey(), r => r.Range)
.Select((g, ix) => new KeyValuePair <string, AlphabetLetter <TLetter> >(g.Key, new AlphabetLetter <TLetter>(new LetterId(ix + 1), new RangeSet <TLetter>(g))))
.ToDictionary(p => p.Key, p => p.Value);
// Step 4: Store alphabet entries for each regex part
foreach (var range in ranges)
{
var alphabetEntry = alphabetByKey[range.GetUsersKey()];
for (var rangeUser = range.Users; rangeUser != null; rangeUser = rangeUser.Next)
{
charsets[rangeUser.User].Value.Add(alphabetEntry.Id);
}
}
// Step 5: store alphabet information
this.AlphabetById = alphabetByKey.Values.ToDictionary(e => e.Id, e => e.Ranges);
this.AlphabetById.Add(LetterId.Eof, eofRange); // EOF
// Step 6: rebuild expression
this.Expression = expression.Visit(new AlphabetLetterVisitor <TLetter>(), node => charsets[visitor.GetId(node)].Value);
}
public static Nfa <TLetter> Build(RxNode <TLetter> node)
{
var builder = new NfaBuilder <TLetter>();
var endState = node.Visit(builder, builder.startState);
return(new Nfa <TLetter>(builder.states, builder.startState, endState));
}
public static RxNode <TLetter> Extract(RxNode <TLetter> rx, SymbolId symbolId)
{
return(rx.Visit(new RxOfSymbol <TLetter>(), symbolId));
}