Fsharp.Core :: {Array;List;Set;Array.Parallel} partitionWith (taking Choice<T,U> partitioner)

[T-Gro]

Implements fsharp/fslang-suggestions#1119

Signatures

module Array =
    val inline partitionWith: partitioner: ('T -> Choice<'T1, 'T2>) -> array: 'T array -> 'T1 array * 'T2 array

module Array.Parallel =
    val inline partitionWith: partitioner: ('T -> Choice<'T1, 'T2>) -> array: 'T array -> 'T1 array * 'T2 array

module List =
    val inline partitionWith: partitioner: ('T -> Choice<'T1, 'T2>) -> list: 'T list -> 'T1 list * 'T2 list

module Set =
    val partitionWith: partitioner: ('T -> Choice<'T1, 'T2>) -> set: Set<'T> -> Set<'T1> * Set<'T2>

Example — active patterns

A total active pattern (|A|B|) is already 'T -> Choice<'T1, 'T2> — pass it directly.

let (|Valid|Invalid|) (s: string) =
    match System.Int32.TryParse s with
    | true, n -> Valid n
    | _ -> Invalid s

let parsed, errors =
    ["42"; "hello"; "7"; "oops"; "99"]
    |> List.partitionWith (|Valid|Invalid|)

// parsed = [42; 7; 99]
// errors = ["hello"; "oops"]

[github-actions]

❗ Release notes required

---

✅ Found changes and release notes in following paths:

Warning

No PR link found in some release notes, please consider adding it.

Change path	Release notes path	Description
src/FSharp.Core	docs/release-notes/.FSharp.Core/10.0.300.md	No current pull request URL (#19335) found, please consider adding it

[Happypig375]

No Choice<'a, 'b, 'c> or Choice<'a, 'b, 'c, 'd> versions?

[T-Gro]

No Choice<'a, 'b, 'c> or Choice<'a, 'b, 'c, 'd> versions?

fsharp/fslang-suggestions#1119 (comment)

But your question made me realize that if we wanted to support all various sorts (all the 7 choices, and result,..), it could be solved by a language-level facility that inverts collection of N-case DU items, and puts them into N different collections of respective fields of those cases.

Maybe more on the "type provider generate types+members from existing types" side ... ?