Function Composition Demo

SizeOfFolder01.fs

open System.IO

let sizeOfFolderComposed folder =
  let getFiles folder =
    Directory.GetFiles(folder, "*.*", SearchOption.AllDirectories)

  let totalSize =
    folder
    |> getFiles
    |> Array.map (fun file -> new FileInfo(file))
    |> Array.map (fun info -> info.Length)
    |> Array.sum

  // The last statement of function will be used as return statement
  totalSize

SizeOfFolder02.fs

open System.IO

let sizeOfFolderComposed folder =
  let getFiles folder =
    Directory.GetFiles(folder, "*.*", SearchOption.AllDirectories)

  // This serves as the last return statement
  getFiles
  >> Array.map (fun file -> new FileInfo(file))
  >> Array.map (fun info -> info.Length)
  >> Array.sum