public static Parser <List <T>, TToken> Many <T, TToken>(this Parser <T, TToken> parser, int least = 0, int most = int.MaxValue)
{
if (parser is null)
{
throw new ArgumentNullException(nameof(parser));
}
return(input =>
{
List <T> elements = new List <T>();
LexemeString <TToken> remainder = input;
for (int i = 0; i <= most; i++)
{
var result = parser(remainder);
if (!result.IsSuccessful)
{
if (i < least)
{
return ParserResult.Error <T, List <T>, TToken>(result);
//return ParserResult.Error<List<T>, TToken>("Too few elements. Expected at least " + least, remainder);
}
return ParserResult.Success(elements, remainder);
}
elements.Add(result.Result);
remainder = result.RemainingLexemes;
}
return ParserResult.Success(elements, remainder);
});
}
/// <summary> /// Returns a parser success of <paramref name="value"/>. /// </summary> /// <typeparam name="T">The return type of the parser.</typeparam> /// <typeparam name="TToken">The type of the tokens.</typeparam> /// <param name="value">The value to succeed with.</param> /// <returns>The parser created.</returns> public static Parser <T, TToken> Value <T, TToken>(T value) => input => ParserResult.Success(value, input);
/// <summary>
/// Parses a singular lexeme from the input and advances the input by one.
/// Returns an error with <paramref name="errorMessage"/> if the input is empty.
/// </summary>
/// <typeparam name="TToken">The type of the tokens.</typeparam>
/// <param name="errorMessage">The error message to return.</param>
/// <returns>The parser created.</returns>
public static Parser <Lexeme <TToken>, TToken> One <TToken>(string errorMessage) =>
input =>
input.Length == 0
? ParserResult.Error <Lexeme <TToken>, TToken>(errorMessage, input)
: ParserResult.Success(input[0], input.Advance(1));