Alastair Reid wrote:
Simon Peyton-Jones <[EMAIL PROTECTED]> writes:that's reasonable. incidently i think (but am not 100% on this) that one can still do most of the work one module at a time. it seems that only type checking needs to happen one strongly connected module component at a time.
Nothing deep. GHC is just a fairly big thing and one of its assumptions is that it is compiling one module at a time. There'd be quite a bit of chuffing around to remove this assumption. Nothing fundamental, but real work.
you only need to type check one strongly connected component of modules at a time. of course it could be the case that your whole program is one big strongly connected component, but that is not that easy to achieve. along those lines - it is of course possible to write a program where all *functions* are mutually recursive, but we don't usually do that.The other big problem is that, in the worst case, you need to typecheck the entire program (however many modules that may be) at once. If your program happens to be GHC, Lolita or one of the other big Haskell programs, this might be prohibitively expensive.
in fact it is very likely that most nontrivial programs have at least two SCCs as it is not usual to import the Main module in other moudles. and of course, most of the time modules don't need to be recusrive and then each module is in a SCC of its own. i very much doubt that GHC has more than a few modules per SCC, but perhaps one of the simons can give us a more definitive answer on that.
bye iavor
-- ================================================== | Iavor S. Diatchki, Ph.D. student | | Department of Computer Science and Engineering | | School of OGI at OHSU | | http://www.cse.ogi.edu/~diatchki | ==================================================
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