/// <summary>
/// Attempts to execute a transducer with content from a <see cref="StringCodeReader" />. If the
/// state reached is not a terminal state, the reader is rewinded to it's initial position.
/// </summary>
/// <typeparam name="OutputT"></typeparam>
/// <param name="transducer"></param>
/// <param name="reader"></param>
/// <param name="output"></param>
/// <returns>Whether the state reached was a terminal state.</returns>
public static Boolean TryExecute <OutputT>(this Transducer <Char, OutputT> transducer, ICodeReader reader, [MaybeNull] out OutputT output)
{
if (transducer is null)
{
throw new ArgumentNullException(nameof(transducer));
}
if (reader is null)
{
throw new ArgumentNullException(nameof(reader));
}
var start = reader.Position;
TransducerState <Char, OutputT> state = transducer.InitialState;
while (reader.Position != reader.Length)
{
if (!state.TransitionTable.TryGetValue(reader.Peek() !.Value, out TransducerState <Char, OutputT>?tmp))
{
break;
}
state = tmp;
reader.Advance(1);
}
if (state.IsTerminal)
{
output = state.Output;
return(true);
}
reader.Restore(start);
// Since the analyzer doesn't seems to obey [MaybeNull], we ignore the warning
output = default;
return(false);
}
/// <inheritdoc/>
public Option <Token <TTokenType> > TryConsume(ICodeReader reader, DiagnosticList diagnostics)
{
if (reader is null)
{
throw new ArgumentNullException(nameof(reader));
}
var start = reader.Position;
reader.Advance(Prefix.Length);
return(new Token <TTokenType>(
_id,
_type,
new Range <int>(start, reader.Position),
_isTrivia,
_value,
Prefix));
}
/// <inheritdoc/>
public Option <Token <TTokenType> > TryConsume(ICodeReader reader, DiagnosticList diagnostics)
{
if (reader is null)
{
throw new ArgumentNullException(nameof(reader));
}
var start = reader.Position;
var result = _expression != null?reader.PeekRegex(_expression) : reader.PeekRegex(_regex !);
if (result.Success)
{
reader.Advance(result.Length);
return(new Token <TTokenType>(
_id,
_type,
new Range <int>(start, reader.Position),
_isTrivia,
_converter != null ? _converter(result, diagnostics) : result.Value,
result.Value));
}
return(default);