Re: [Haskell-cafe] Reification in Haskell, was: To yi or not to yi
Hi Bulat, do you mean that as the type information is used only at compilation time and then thrown away there is no way of getting it back at execution time? best, titto On Wednesday 20 June 2007 16:33:12 Bulat Ziganshin wrote: Hello Pasqualino, Wednesday, June 20, 2007, 11:30:32 AM, you wrote: Most languages, even Java, have a reflection capability to dynamically inspect an object. It is surprising that Haskell doesn't offer it. how about asm? :) there are no OOP objects in Haskell, each name is just an address of memory area. all operations are checked statically (at compile time). reflection capabilities may be only handmade - you can get any type info via hidden class dictionary (see http://homepages.inf.ed.ac.uk/wadler/papers/class/class.ps.gz for details of type classes implementation) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[2]: [Haskell-cafe] Reification in Haskell, was: To yi or not to yi
Hello Pasqualino, Thursday, June 21, 2007, 11:22:19 AM, you wrote: more or less. there are Data and Typeable classes that provides this information but to use them you 1) should use GHC 2) should add deriving Typeable clause to declaration of each type you need to inspect 3) have Typeable a condition in definition of each function where you need this information: print_type :: (Typeable a) = a - IO () so, its just something like class definition: class Typeable a where typename :: a - String with GHC automatically deriving instances of this class. no real RTTI because Haskell data items are not objects. i suggest you to read paper before asking more questions :) do you mean that as the type information is used only at compilation time and then thrown away there is no way of getting it back at execution time? best, titto On Wednesday 20 June 2007 16:33:12 Bulat Ziganshin wrote: Hello Pasqualino, Wednesday, June 20, 2007, 11:30:32 AM, you wrote: Most languages, even Java, have a reflection capability to dynamically inspect an object. It is surprising that Haskell doesn't offer it. how about asm? :) there are no OOP objects in Haskell, each name is just an address of memory area. all operations are checked statically (at compile time). reflection capabilities may be only handmade - you can get any type info via hidden class dictionary (see http://homepages.inf.ed.ac.uk/wadler/papers/class/class.ps.gz for details of type classes implementation) -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Reification in Haskell, was: To yi or not to yi
Hi everybody, What is the situation with respect to reification of function/thunks in Haskell? Does any current implementation support it ? And, is there any plan for GHC to support it? Claus's comments on this, follow. titto On Monday 18 June 2007 23:45:23 Claus Reinke wrote: Is there any fundamental reasons why Haskell functions/closures cannot be serialised? no, and that is part of the problem: the language would need to be extended, but the academically interesting issues have been tackled, all that is left is a lot of work (that is why these things would be so valuable: complex implementation machinery, controlled by very small language extensions, sometimes even language simplifications, such as lifting existing restrictions on i/o), preferably with very good planning, so that all the work does not become useless right after it is finished. there isn't much hope that this issue is going to be settled via the usual academic funding sources. Most languages, even Java, have a reflection capability to dynamically inspect an object. It is surprising that Haskell doesn't offer it. it has to be done with care, or it will invalidate *all* your nice reasoning about haskell programs. random example reify (f . g) == [| f . g |] =/= [| \x- f (g x) |] == reify (\x- f (g x)) reification is not a referentially transparent program context. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Reification in Haskell, was: To yi or not to yi
Hello Pasqualino, Wednesday, June 20, 2007, 11:30:32 AM, you wrote: Most languages, even Java, have a reflection capability to dynamically inspect an object. It is surprising that Haskell doesn't offer it. how about asm? :) there are no OOP objects in Haskell, each name is just an address of memory area. all operations are checked statically (at compile time). reflection capabilities may be only handmade - you can get any type info via hidden class dictionary (see http://homepages.inf.ed.ac.uk/wadler/papers/class/class.ps.gz for details of type classes implementation) -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
