dotnet-coding-languageext

Each conversion is a method on the source type named for the target, such as ToFin, ToValidation, ToOption, and ToEither. Converting from Option requires supplying the Error it lacks, for example value.ToFin(new NotFound()).

Use the Catch overload that selects by code: quantity.Catch(Codes.InvalidQuantity, _ => fallback). Code and error-value overloads return K<F, A>, so append .As() to restore the concrete type like Fin<A> or IO<A>.

Fin short-circuits on the first failure while Validation accumulates failures through its Apply using the Error monoid. Convert Fin to Validation before combining independent validations, and convert back to Fin when input validation ends.

Yes. Effects built with IO.liftAsync overlap without a bound, and Traverse under IO starts every element effect before awaiting any. For bounded parallelism, chunk the collection and traverse the chunks with TraverseM.

Contains, Sum, and Average on Seq are ambiguous with LINQ extensions, producing CS0121. Use Exists for membership and Fold for sums, and sort with LINQ Order() followed by toSeq since Seq has no Sort instance.

Use transformers when a workflow needs two effects in one expression, such as IO with optional results, since Bind cannot cross higher-kinded types. OptionT<IO, A> stores K<IO, Option<A>> and liftIO forwards IO actions through every layer.