Hi guys I need to migrate this to arrow 1.0: ```Validated.applicative(validationSemigroup).tupled(Va...

# arrow

[Alvaro Blazquez checa]

Hi guys I need to migrate this to arrow 1.0:

Validated.applicative(validationSemigroup).tupled(Valid("foo"), Valid("bar")).fix()

[Alvaro Blazquez checa]

where:

val validationSemigroup: Semigroup<List<WebError>> = object : Semigroup<List<WebError>> {
    override fun List<WebError>.combine(b: List<WebError>): List<WebError> =
        Stream.concat(stream(), b.stream()).toList()
}

[Alvaro Blazquez checa]

I have tried to do it with zip

[Alvaro Blazquez checa]

like:

Valid("foo").zip(Valid("bar"), ::Pair)

[simon.vergauwen]

val validationSemigroup: Semigroup<List<WebError>> = object : Semigroup<List<WebError>> {
    override fun List<WebError>.combine(b: List<WebError>): List<WebError> =
        this + b
}

Valid("foo").zip(validationSemigroup, Valid("bar"), ::Pair)

[Alvaro Blazquez checa]

but zip method compains

[simon.vergauwen]

There is also no need to use Stream.concat inside Semigroup you can just use List.plus from Kotlin.

[simon.vergauwen]

If you’re working with ValidatedNel you can omit the semigroup parameter to zip.

[simon.vergauwen]

Which is probably more interesting for you too, since having List inside Invalid means it can also contain an empty list of errors, which typically isn’t possible.

[simon.vergauwen]

NonEmptyList is just like List but has a minimum size of 1 instead of 0. It has special support for Validated in for example zip.

[Alvaro Blazquez checa]

That last part makes total sense

[Alvaro Blazquez checa]

and thank you for the qucik respone Simon. I am trying that

[Alvaro Blazquez checa]

Also forces web validations users to always return a list with at least one Weberror when it exist

[Alvaro Blazquez checa]

great