sequenceResultM

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sequenceResultM

List.sequenceResultM
Namespace: FsToolkit.ErrorHandling
Function Signature:
Result<'a, 'b> list -> Result<'a list, 'b>
Note that sequence is the same as traverse id. See also List.traverseResultM.
This is monadic, stopping on the first error. Compare the example below with sequenceResultA.
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.map tryParseInt
|> List.sequenceResultM 
// Ok [1; 2; 3]
​
["1"; "foo"; "3"; "bar"]
|> List.map tryParseInt
|> List.sequenceResultM  
// Error "unable to parse 'foo' to integer"

traverseResultM

traverseResultA

Last modified 9mo ago

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Outline

List.sequenceResultM

Examples