program shannon_entropy;
    print(entropy "1223334444");

    op entropy(symbols);
        hist := {};
        loop for symbol in symbols do
            hist(symbol) +:= 1;
        end loop;
        h := 0.0;
        loop for count = hist(symbol) do
            f := count / #symbols;
            h -:= f * log f / log 2;
        end loop;
        return h;
    end op;
end program;