I’ve just finished writing out almost 20 pages of math to hand in tomorrow. Fun fun fun. There are some wholly unsatisfactory answers but they’ll have to do. My favourite runs along the lines of “the functions that can be expressed in this way are all the functions that can be expressed in this way”. But of course in fancy mathematical symbols so at least it doesn’t look stupid to people who don’t know what it all means. And that’s really the point, now, isn’t it?