public override ReadResult <Alternative> Read(ITextScanner scanner)
{
if (scanner == null)
{
throw new ArgumentNullException(nameof(scanner));
}
var context = scanner.GetContext();
ILexer bestCandidate = null;
var bestCandidateLength = -1;
var ordinal = 0;
IList <SyntaxError> errors = new List <SyntaxError>(lexers.Length);
SyntaxError partialMatch = null;
// ReSharper disable once ForCanBeConvertedToForeach
for (var i = 0; i < lexers.Length; i++)
{
var lexer = lexers[i];
var candidate = lexer.ReadElement(scanner);
if (candidate.Success)
{
var alternative = candidate.Element;
var length = alternative.Text.Length;
if (length > bestCandidateLength)
{
bestCandidate = lexer;
bestCandidateLength = length;
ordinal = i + 1;
}
if (length != 0)
{
scanner.Unread(alternative.Text);
}
}
else
{
errors.Add(candidate.Error);
if (partialMatch == null || candidate.Text.Length > partialMatch.Text.Length)
{
partialMatch = candidate.Error;
}
}
}
if (bestCandidate == null)
{
Debug.Assert(partialMatch != null, "partialMatch != null");
return(ReadResult <Alternative> .FromSyntaxError(partialMatch));
}
var readResult = bestCandidate.ReadElement(scanner);
Debug.Assert(readResult.Success, "readResult.Success");
return(ReadResult <Alternative> .FromResult(new Alternative(readResult.Text, readResult.Element, context, ordinal)));
}
public override ReadResult <Repetition> Read(ITextScanner scanner)
{
if (scanner == null)
{
throw new ArgumentNullException(nameof(scanner));
}
var context = scanner.GetContext();
var stringBuilder = new StringBuilder();
IList <Element> elements = new List <Element>(lowerBound);
// ReSharper disable once ForCanBeConvertedToForeach
for (var i = 0; i < upperBound; i++)
{
var readResult = lexer.ReadElement(scanner);
if (readResult.Success)
{
elements.Add(readResult.Element);
stringBuilder.Append(readResult.Text);
}
else
{
if (elements.Count >= lowerBound)
{
return
(ReadResult <Repetition> .FromResult(
new Repetition(stringBuilder.ToString(), elements, context)));
}
var partialMatch = stringBuilder.ToString();
if (partialMatch.Length != 0)
{
scanner.Unread(partialMatch);
}
return
(ReadResult <Repetition> .FromSyntaxError(
new SyntaxError(
readResult.EndOfInput,
partialMatch,
readResult.ErrorText,
context,
readResult.Error)));
}
}
return(ReadResult <Repetition> .FromResult(new Repetition(stringBuilder.ToString(), elements, context)));
}
