traverseResultM

List.traverseResultM

Namespace: FsToolkit.ErrorHandling

Function Signature:

('a -> Result<'b,'c>) -> 'a list -> Result<'b list, 'c>

Note that traverse is the same as map >> sequence. See also List.sequenceResultM.

This is monadic, stopping on the first error. Compare the example below with traverseResultA.

See also Scott Wlaschin's Understanding traverse and sequence.

Examples

Example 1

// string -> Result<int, string>
let tryParseInt str =
match Int32.TryParse str with
| true, x -> Ok x
| false, _ ->
Error (sprintf "unable to parse '%s' to integer" str)
["1"; "2"; "3"]
|> List.traverseResultM tryParseInt
// Ok [1; 2; 3]
["1"; "foo"; "3"; "bar"]
|> List.traverseResultM tryParseInt
// Error "unable to parse 'foo' to integer"