how to get latest x directory folder entries using F#

Question

I was stuck trying to figure out a method of getting the latest n folders in a particular root directory using F#. The code below is the outcome of that journey and I wanted to post here and share the code sample to help other engineers trying to solve a similar problem.

open System  
open System.IO  

// only get the N latest FOLDERS in a directory    
let getLatestNFolders (rootDirectory:string) (howmany:int) =  
    let latestFolders =  
        Directory.GetDirectories(rootDirectory)   
        |> Seq.cache  
        |> Seq.map(fun filePath -> (filePath,   Directory.GetCreationTime(filePath)))  
        |> Seq.sortBy(fun (path, time) -> -time.Ticks) // descending order  
        |> Seq.take(howmany)
        |> Seq.map(fun (path, time) -> path)  
        |> Set.ofSeq  
    latestFolders  

let results =  getLatestNFolders "c:\\temp" 3

results |> Seq.iter(fun path -> printfn "%s\n" path)

Answer 1

Here are some improvements, mostly focused on removing some cruft:

// only get the N latest FOLDERS in a directory    
let getLatestNFolders (rootDirectory:string) howmany =  
    Directory.GetDirectories(rootDirectory)   
    |> Seq.sortBy(fun path -> -Directory.GetCreationTime(path).Ticks) // descending order  
    |> Seq.take howmany