On Wed, Nov 02, 2005 at 04:27:03PM +0100, Daan Leijen wrote: > Hi David,
Hello, > One way of dealing with constant pointer is to introduce (yet another) > phantom type variable 'r' to pointers: ... > And we can derive the "const" attribute too: > > data FooPtr r = FooPtr String (Ptr r Foo) This is indeed very cool (and much better than I was imagining), but it seems like there may still be one problem. It seems to me that a bad person could escape the "constness" feature using the RULES pragma. So if all I knew was that hsstrcat had signature > strcat :: Ptr Write CChar -> Ptr r CChar -> IO () then I wouldn't have a guarantee that strcat isn't specialized for writeable Ptrs, in which case it might have the result of modifying a pointer when I don't want it to. Admittedly, this isn't a likely scenario, but when I have the typechecker check something, I'd like it to give me a guarantee, with the usual caveat that certain "unsafe" functions aren't called. Does the RULES pragma fall in that "unsafe" category? -- David Roundy _______________________________________________ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
