entropy = function(s)
    count = {}
    for c in s
        if count.hasIndex(c) then count[c] = count[c]+1 else count[c] = 1
    end for
    sum = 0
    for x in count.values
        countOverN = x / s.len
        sum = sum + countOverN * log(countOverN, 2)
    end for
    return -sum
end function

print entropy("1223334444")