' version 25-06-2015
' compile with: fbc -s console

Sub calc_entropy(source As String, base_ As Integer)

    Dim As Integer i, sourcelen = Len(source), totalchar(255)
    Dim As Double prop, entropy

    For i = 0 To sourcelen -1
        totalchar(source[i]) += 1
    Next

    Print "Char    count"
    For i = 0 To 255
        If totalchar(i) = 0 Then Continue For
        Print "   "; Chr(i); Using "   ######"; totalchar(i)
        prop = totalchar(i) / sourcelen
        entropy = entropy - (prop * Log (prop) / Log(base_))
    Next

    Print : Print "The Entropy of "; Chr(34); source; Chr(34); " is"; entropy

End Sub

' ------=< MAIN >=------

calc_entropy("1223334444", 2)
Print

' empty keyboard buffer
While InKey <> "" : Wend
Print : Print "hit any key to end program"
Sleep
End