F# split array of strings and return the result of split

Question

let total = [| "1X2"; "3X4"; "5X6" |]

let oddEven = total
            |> Array.map(fun x -> x.Split('X'))

I have an array of string, which is total in above example, I want to split the array by "X", as the oddEven in the above example, but I want to return 2 arrays of strings:

let odd = [| 1; 3; 5 |] and let even = [| 2; 4; 6 |]

It could be an easy task, but I can not figure it out now. Any help is greatly appreciated! Thanks,

pad · Accepted Answer · 2011-10-29 21:58:41Z

4

You should check whether each string can split into two pieces, and unzip the result:

let total = [| "1X2"; "3X4"; "5X6" |]

let odds, evens = total |> Array.map (fun x ->  match x.Split('X') with
                                                | [|odd; even|] -> odd, even
                                                | _ -> failwith "Wrong input")
                        |> Array.unzip;;

answered Oct 29, 2011 at 21:58

pad

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3 Comments

John John Over a year ago

Thank you very much for your great code! Besides, it is very good that your code did a careful condition check, otherwise, there could be some wrong input to ruin the results! Thanks and have a nice weekend!

swapneel Over a year ago

Assuming this is numeric odd and even - above solution will not work correctly for let total = [| "2X1"; "3X4"; "6X8" |]

pad Over a year ago

I assume the solution is for odd and even positions in each split string array.

Rune FS · Accepted Answer · 2011-10-30 11:49:18Z

2

let evens, odds = total 
                  |> (Array.map (fun x -> x.Split('X')))
                  |> Array.concat
                  |> Array.partition (fun s -> int s % 2 = 0)

EDIT: As John Palmer points out in the comments, you can use Array.collect instead of map and concat:

let evens, odds = total 
                    |> Array.collect (fun s -> s.Split('X')) 
                    |> Array.partition (fun s -> int s % 2 = 0);;

edited Oct 30, 2011 at 11:49

Rune FS

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answered Oct 29, 2011 at 22:13

Lee

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4 Comments

swapneel Over a year ago

|> (Array.map (fun x -> x.Split('X'))) ----^^ stdin(26,5): error FS0010: Unexpected infix operator in binding. Expected incomplete structured construct at or before this point or other token.

Lee Over a year ago

@swapneel - I think it's an indentation problem - try indenting the lines after the first so they level with 'total' in the first.

John Palmer Over a year ago

@Lee - You can youse Array.collect rather than Array.map ... |> Array.concat

Lee Over a year ago

@JohnPalmer - Thanks, I wasn't aware of collect.

BLUEPIXY · Accepted Answer · 2011-10-30 11:18:20Z

0

let odd = 
    oddEven |> Array.map (fun x -> x.[0])
let even =
    oddEven |> Array.map (fun x -> x.[1])

answered Oct 30, 2011 at 11:18

BLUEPIXY

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2 Comments

Rune FS Over a year ago

x.[1] is always 'X' and wouldn't really work with numbers larger than 9

BLUEPIXY Over a year ago

You might just have misunderstood? oddEven is [|[|"1"; "2"|]; [|"3"; "4"|]; [|"5"; "6"|]|]

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