Parse.EnumerateInput.cs

//in Parse.cs
public static Parser<U> EnumerateInput<T, U>(IEnumerable<T> input, Func<T, Parser<U>> parser)
{
    if (input == null) throw new ArgumentNullException("input");
    if (parser == null) throw new ArgumentNullException("parser");

    return EnumerateInput(input.ToArray(), parser);
}

public static Parser<U> EnumerateInput<T, U>(T[] input, Func<T, Parser<U>> parser)
{
    if (input == null || input.Length == 0) throw new ArgumentNullException("input");
    if (parser == null) throw new ArgumentNullException("parser");

    return i =>
    {
        var res = (IResult<U>)(new Result<U>(null, null, null));
        foreach (var inp in input)
        {
            res = parser(inp)(i);
            if (res.WasSuccessful) return res;
        }

        return res;
    };
}