on pickNumber()
   set theNumber to ""
   repeat 4 times
      set theDigit to (random number from 1 to 9) as string
      repeat while (offset of theDigit in theNumber) > 0
         set theDigit to (random number from 1 to 9) as string
      end repeat
      set theNumber to theNumber & theDigit
   end repeat
end pickNumber

to bulls of theGuess given key:theKey
   set bullCount to 0
   repeat with theIndex from 1 to 4
      if text theIndex of theGuess = text theIndex of theKey then
         set bullCount to bullCount + 1
      end if
   end repeat
   return bullCount
end bulls

to cows of theGuess given key:theKey, bulls:bullCount
   set cowCount to -bullCount
   repeat with theIndex from 1 to 4
      if (offset of (text theIndex of theKey) in theGuess) > 0 then
         set cowCount to cowCount + 1
      end if
   end repeat

   return cowCount
end cows

to score of theGuess given key:theKey
   set bullCount to bulls of theGuess given key:theKey
   set cowCount to cows of theGuess given key:theKey, bulls:bullCount
   return {bulls:bullCount, cows:cowCount}
end score

on run
   set theNumber to pickNumber()
   set pastGuesses to {}
   repeat
      set theMessage to ""
      repeat with aGuess in pastGuesses
         set {theGuess, theResult} to aGuess
         set theMessage to theMessage & theGuess & ":" & bulls of theResult & "B, " & cows of theResult & "C" & linefeed
      end repeat
      set theMessage to theMessage & linefeed & "Enter guess:"
      set theGuess to text returned of (display dialog theMessage with title "Bulls and Cows" default answer "")
      set theScore to score of theGuess given key:theNumber
      if bulls of theScore is 4 then
         display dialog "Correct!  Found the secret in " & ((length of pastGuesses) + 1) & " guesses!"
         exit repeat
      else
         set end of pastGuesses to {theGuess, theScore}
      end if
   end repeat
end run