public static void Derive([NotNull, ItemNotNull] this List <Symbol> tape, [NotNull] GrammarType0 grammar,
[NotNull] IDerivationTracker tracker)
{
while (tape.TryDerive(grammar, tracker))
{
}
}
private static bool TryDerive([NotNull, ItemNotNull] this List <Symbol> tape, [NotNull] GrammarType0 grammar,
[NotNull] IDerivationTracker tracker)
{
if (!grammar.Rules.Any(rule => TryDerive(tape, rule, tracker)))
{
return(false);
}
return(true);
}
private static bool TryDerive([NotNull, ItemNotNull] List <Symbol> tape,
int start,
[NotNull] GrammarRule0 rule, IDerivationTracker tracker)
{
if (tape.Count < start + rule.LeftHandSide.Count)
{
return(false);
}
var sublist = tape.GetRange(start, rule.LeftHandSide.Count);
if (!sublist.SequenceEqual(rule.LeftHandSide))
{
return(false);
}
tape.RemoveRange(start, rule.LeftHandSide.Count);
tape.InsertRange(start, rule.RightHandSide);
tracker.Track(tape, rule);
return(true);
}
public static bool TryDerive([NotNull, ItemNotNull] this List <Symbol> tape, [NotNull] GrammarRule0 rule,
IDerivationTracker tracker) =>
tape.Where((t, index) => TryDerive(tape, index, rule, tracker)).Any();
