some computation so we wanted to solve some kind of problem that is taking an algorithm at an input we have to be very careful of how we do this I mean like if you just took the usual kind of algorithm as input like the sort of terrain type algorithm then there are lots of results an undergrad computability theory that just says no matter what you try to do analyzing the things it's not going to work so it's make this kind of connection tractable we have to slightly change the model of algorithm we're looking at and