haskell

import Graphics.UI.Gtk


main :: IO ()
main = do
   initGUI
   window <- windowNew
   set window [windowTitle:="Operaciones sencillas", containerBorderWidth := 20,
               windowDefaultWidth:=150, windowDefaultHeight:=100]
   table <- tableNew 4 2 True
   containerAdd window table
   label1 <-labelNew (Just "Ingrese un entero positivo:")
   tableAttachDefaults table dataText 0 1 1 2
   button1 <- buttonNewWithLabel "Calcula el factorial"
   tableAttachDefaults table button1 1 2 1 2
   label2 <- labelNew(Just"")
   tableAttachDefaults table button2 0 2 3 4
   onClicked button2 mainQuit
   onClicked button1 (sol dataText label2)
   onDestroy window mainQuit
   widgetShowAll window
   mainGUI

sol :: Entry -> Label -> IO ()
sol dT l2 = do
   txt <- entryGetText dT
   labelSetText l2 ("El factorial de "++ txt ++ " es: " ++ (fact txt))

fact :: String -> String
fact txt = show (product [1.. (read txt :: Int)])