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feat(Seq)!: Add sequenceResultA, align sequenceResultM (#255)
* Roll on '24 * refactor(Seq.sequenceResultM)!: Change Ok to Array * docs: sequenceResultM * feat(Seq): sequenceResultA * f sequenceResultM docs * Supress compile error * Fix proposed version
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# Seq.sequenceResultA | ||
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Namespace: `FsToolkit.ErrorHandling` | ||
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## Function Signature | ||
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```fsharp | ||
seq<Result<'a, 'b>> -> Result<'a[], 'b[]> | ||
``` | ||
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This is applicative, collecting all errors. Compare the example below with [sequenceResultM](sequenceResultM.md). | ||
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See also Scott Wlaschin's [Understanding traverse and sequence](https://fsharpforfunandprofit.com/posts/elevated-world-4/). | ||
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## Examples | ||
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### Example 1 | ||
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```fsharp | ||
// string -> Result<int, string> | ||
let tryParseInt str = | ||
match Int32.TryParse str with | ||
| true, x -> Ok x | ||
| false, _ -> Error $"unable to parse '{str}' to integer" | ||
["1"; "2"; "3"] | ||
|> Seq.map tryParseInt | ||
|> Seq.sequenceResultA | ||
// Ok [| 1; 2; 3 |] | ||
["1"; "foo"; "3"; "bar"] | ||
|> Seq.map tryParseInt | ||
|> Seq.sequenceResultA | ||
// Error [| "unable to parse 'foo' to integer" | ||
// "unable to parse 'bar' to integer" |] | ||
``` | ||
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### Example 2 | ||
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```fsharp | ||
// int -> Result<bool, string> | ||
let isPrime (x: int) = | ||
if x < 2 then Error $"{x} must be greater than 1" | ||
elif x = 2 then Ok true | ||
else | ||
let rec isPrime' (x : int) (i : int) = | ||
if i * i > x then Ok true | ||
elif x % i = 0 then Ok false | ||
else isPrime' x (i + 1) | ||
isPrime' x 2 | ||
// seq<int> -> Result<bool, string[]> | ||
let checkIfAllPrime (numbers: seq<int>) = | ||
seq { for x in numbers -> isPrime x } // Result<bool, string> seq | ||
|> Seq.sequenceResultA // Result<bool[], string[]> | ||
|> Result.map (Seq.forall id) // shortened version of '|> Result.map (fun results -> results |> Array.forall (fun x -> x = true))' | ||
let a = [| 1; 2; 3; 4; 5 |] |> checkIfAllPrime | ||
// Error [| "1 must be greater than 1" |] | ||
let b = [ 1; 2; 3; 4; 5; 0 ] |> checkIfAllPrime | ||
// Error [| "1 must be greater than 1"; "0 must be greater than 1" |] | ||
let a = seq { 2; 3; 4; 5 } |> checkIfAllPrime | ||
// Ok false | ||
let a = seq { 2; 3; 5 } |> checkIfAllPrime | ||
// Ok true | ||
``` |
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# Seq.sequenceResultM | ||
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Namespace: `FsToolkit.ErrorHandling` | ||
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## Function Signature | ||
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```fsharp | ||
seq<Result<'a, 'b>> -> Result<'a[], 'b> | ||
``` | ||
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This is monadic, stopping on the first error. Compare the example below with [sequenceResultA](sequenceResultA.md). | ||
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See also Scott Wlaschin's [Understanding traverse and sequence](https://fsharpforfunandprofit.com/posts/elevated-world-4/). | ||
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## Examples | ||
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### Example 1 | ||
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```fsharp | ||
// string -> Result<int, string> | ||
let tryParseInt str = | ||
match Int32.TryParse str with | ||
| true, x -> Ok x | ||
| false, _ -> Error $"unable to parse '{str}' to integer" | ||
["1"; "2"; "3"] | ||
|> Seq.map tryParseInt | ||
|> Seq.sequenceResultM | ||
// Ok [| 1; 2; 3 |] | ||
seq { "1"; "foo"; "3"; "bar" } | ||
|> Seq.map tryParseInt | ||
|> Seq.sequenceResultM | ||
// Error "unable to parse 'foo' to integer" | ||
``` | ||
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### Example 2 | ||
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```fsharp | ||
// int -> Result<bool, string> | ||
let isPrime (x: int) = | ||
if x < 2 then Error $"{x} must be greater than 1" | ||
elif x = 2 then Ok true | ||
else | ||
let rec isPrime' (x : int) (i : int) = | ||
if i * i > x then Ok true | ||
elif x % i = 0 then Ok false | ||
else isPrime' x (i + 1) | ||
isPrime' x 2 | ||
// int seq -> Result<bool, string[]> | ||
let checkIfAllPrime (numbers: seq<int>) = | ||
numbers | ||
|> Seq.map isPrime // seq<Result<bool, string>> | ||
|> Seq.sequenceResultM // Result<bool[], string> | ||
|> Result.map (Array.forall id) // shortened version of '|> Result.map (fun bools -> bools |> Array.forall (fun x -> x = true))' | ||
let a = [ 1; 2; 3; 4; 5 ] |> checkIfAllPrime | ||
// Error [| "1 must be greater than 1" |] | ||
let b = [| 1; 2; 3; 4; 5; 0 |] |> checkIfAllPrime | ||
// Error [| "1 must be greater than 1" |] | ||
let a = seq { 2; 3; 4; 5 } |> checkIfAllPrime | ||
// Ok false | ||
let a = [2; 3; 5;] |> checkIfAllPrime | ||
// Ok true | ||
``` |
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Original file line number | Diff line number | Diff line change |
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namespace FsToolkit.ErrorHandling | ||
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[<RequireQualifiedAccess>] | ||
module Seq = | ||
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let sequenceResultM (xs: seq<Result<'t, 'e>>) : Result<'t seq, 'e> = | ||
let rec loop xs ts = | ||
match Seq.tryHead xs with | ||
| Some x -> | ||
x | ||
|> Result.bind (fun t -> loop (Seq.tail xs) (t :: ts)) | ||
| None -> | ||
Ok( | ||
List.rev ts | ||
|> List.toSeq | ||
) | ||
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// Seq.cache prevents double evaluation in Seq.tail | ||
loop (Seq.cache xs) [] | ||
module FsToolkit.ErrorHandling.Seq | ||
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let sequenceResultM (xs: seq<Result<'t, 'e>>) : Result<'t[], 'e> = | ||
if isNull xs then | ||
nullArg (nameof xs) | ||
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let acc = ResizeArray() | ||
let mutable err = Unchecked.defaultof<_> | ||
let mutable ok = true | ||
use e = xs.GetEnumerator() | ||
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while ok | ||
&& e.MoveNext() do | ||
match e.Current with | ||
| Ok r -> acc.Add r | ||
| Error e -> | ||
ok <- false | ||
err <- e | ||
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if ok then Ok(acc.ToArray()) else Error err | ||
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let sequenceResultA (xs: seq<Result<'t, 'e>>) : Result<'t[], 'e[]> = | ||
if isNull xs then | ||
nullArg (nameof xs) | ||
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let oks = ResizeArray() | ||
let errs = ResizeArray() | ||
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for x in xs do | ||
match x with | ||
| Ok r -> oks.Add r | ||
| Error e -> errs.Add e | ||
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match errs.ToArray() with | ||
| [||] -> Ok(oks.ToArray()) | ||
| errs -> Error errs |
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