Hello, > Interesting. `verify' seems to be a form of contracts: > > http://ftp.ccs.northeastern.edu/scheme/pubs/icfp2002-ff.pdf > > Does `verify' have runtime semantics? Under what situations, if any, > would the compiler insert runtime checks?
It has no runtime semantics right now. I considered making it like 'assert', but I'm not sure that's right. I will look at that paper. > As that paper indicates, two issues you will have to deal with are > higher-order functions and blame. > > Your interest in static analysis naturally raises the question of types. > You might like this paper: > > http://www.ccs.neu.edu/racket/pubs/dls06-tf.pdf I will look at that too; thank you. > Ah, I was just curious. I made some small changes relative to > stable-2.0 (primcall and seq), and wondered if they were a good idea or > not. > > I was also considering a move to a CPS-based intermediate language. > Some links are here: > > http://wingolog.org/archives/2011/07/12/static-single-assignment-for-functional-programmers Oh, this is interesting. I was just wondering if I needed a CPS-type representation to write the analyzer reasonably elegantly. If you think the main compiler also needs it, then perhaps I should work on that first, and then come back to the analyzer question. I do think there's a problem with plain CPS, though - it forces you to pick an order for the evaluation of function arguments. I would like to use CPS with some sort of parallel-call operator, so we can leave the order undefined (maybe at some point an optimizer will want to adjust the order). What do you think? I also noticed that at the end of that blog post you said you were considering ANF versus CPS for Guile (I assume you'd already decided that you didn't like Tree-IL). Does this mean you decided on CPS? >> My first idea was to implement something equivalent to 0-CFA, which >> unfortunately has complexity O(n^3). If there's something that's >> faster and still produces useful results, that could be a good first >> step. However, I also think we could get the average-case time far >> below n^3 by doing inference on demand instead of calculating the type >> of every binding, similar to the change that peval went through a >> couple months ago. > > Yes, this is my thought as well. Note also that peval is described by > waddell and dybvig as being a kind of special-purpose sub-0CFA. That makes sense. What I'd *really* like to do is make the analyzer use the same on-demand-calculation infrastructure as peval, but it might be really tricky to make them fit together. I am planning to leave that project for much later. Noah