Validation on List of Items

I’ve been exploring the Validation class and have it working on validating a single item, but I want to validate each item in a list and return a single Validate item.

Example: I have a list of numbers, and I want to validate each of their lengths is less than 5.

From my understanding, the Error is actually a Seq which is appendable (a monoid?).

Can I get a Validate with any errors appended? I assume the type of Validation would also need to change from Validation<Error, string> to Validation<Error, List<string>> during this transition.

var list = new List<string>() { "1234", "12", "123456" };
var ValidateString = fun((string s) => s.Length < 5 ? Success<Error, string>(s) : Fail<Error, string>(Error.New("Too long")));

// would like a `Validation<Error, List<string>>` back, with both sides aggregated.
IEnumerable<Validation<Error, string>> validList = list.Map(t => ValidateString(t));

IEnumerable<Validation<Error, string>> validList = from i in list
                                                              select ValidateString(i);

 public class Error : NewType<Error, string>
    {
        public Error(string e) : base(e) { }
    }

The real use case is to take a list of emails, validate them, and return the list, if thats of any value.

[gregberns]

Not sure why I didn’t think of that obvious option. Thanks Chris

[trbngr]

I would just use match.

validation.Match(
    Succ: identity,
    Fail: errors => errors.Map(x => x.Value)
);