Result

Reified.Result composes the standard F# Result<'value,'error>; it never wraps or replaces that type. The collection combinators apply a fallible operation across a sequence, stopping at the first error or collecting every one.

Collection traversal signatures

All four take any seq<_> and produce a list:

Result.traverse    : ('a -> Result<'b, 'e>) -> seq<'a> -> Result<'b list, 'e>
Result.sequence    : seq<Result<'a, 'e>> -> Result<'a list, 'e>
Result.traverseAll : ('a -> Result<'b, 'e>) -> seq<'a> -> Result<'b list, 'e list>
Result.sequenceAll : seq<Result<'a, 'e>> -> Result<'a list, 'e list>

traverse maps each item with a Result-returning function and stops at the first failure; sequence is traverse id over a sequence of results. traverseAll and sequenceAll run every mapping in input order and return one error per failing item, in input order. Nothing is flattened: a mapping that itself returns Result<_, 'error list> produces a list of lists, so map it down first.

All four convert the input to a list up front, so a lazy sequence is fully forced and an infinite one will not terminate through any of them.

See Working with collections for the walkthrough.