/// <summary>
/// Creates a parser for an identifier
/// </summary>
/// <returns>the parser</returns>
public static IParser <char, string> Identifier()
{
// identifier:
// available-identifier
// @ identifier-or-keyword
return(Expect.OneOf(
AvailableIdentifier(),
Expect.Concatenation(
Expect.Char('@'),
IdentifierOrKeyWord(),
(at, identifierOrKeyWord) => string.Concat(at, identifierOrKeyWord))
));
}