Core lib parallel Array.chose F#

choose.fs

let choose f (array: 'T[]) = 
                
                let inputLength = array.Length                

                let isChosen : bool [] = Array.zeroCreate inputLength
                let results : 'U [] = Array.zeroCreate inputLength
                
                Parallel.For(0, inputLength, (fun i -> 
                    match f array.[i] with 
                    | None -> () 
                    | Some v -> 
                        isChosen.[i] <- true; 
                        results.[i] <- v
                )) |> ignore         
                                                                                      
                let mutable outputLength = 0                
                for i = 0 to isChosen.Length-1 do 
                    if isChosen.[i] then 
                        outputLength <- outputLength + 1
                        
                let output = Array.zeroCreate outputLength
                let mutable curr = 0
                for i = 0 to isChosen.Length-1 do 
                    if isChosen.[i] then 
                        output.[curr] <- results.[i]
                        curr <- curr + 1
                output