- Glasgow-haskell-users

RE: Or-patterns
by Simon Peyton-Jones 06 Dec '00

06 Dec '00

Sensible suggestion No technical problem, just one more thing to do. If anyone feels inclined to implement it I'll gladly incorporate the fruits of their labours in the GHC code base. Simon | -----Original Message----- | From: George Russell [mailto:ger@Informatik.Uni-Bremen.DE] | Sent: 04 December 2000 16:18 | To: glasgow-haskell-users(a)haskell.org | Subject: Or-patterns | | | Why not steal a good idea from Standard ML/New Jersey now and | again? This has | "Or-patterns" which allow you to match against a disjunction | of patterns, | EG | | fun sleepIn (Date.Sat | Date.Sun) = true | | sleepIn _ = false | | Where you have variables in the patterns, you bind only the | variables which appear | in all the patterns, and you unify the types accordingly. | | Of course you can do without this feature, but I feel it | shouldn't be too hard | to implement and for me at least it would be occasionally useful. | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users(a)haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users |

1 0

The Set type
by George Russell 04 Dec '00

04 Dec '00

A minor quibble I know, but every time I use sets I want to add/subtract single elements to/from them. There is no function provided for doing this, so instead you have to do union/delete with a singleton set constructed from the element. I appreciate the zeal of the designer of this module to construct the smallest possible interface (I wish the same person had designed the standard Prelude) but I think this zeal is overdone. You do often need to operate with single elements. After all, if you wanted real hair-shirt minimalism you should get rid of "elementOf" (replace it by \el set -> isEmptySet (intersect set (singletonSet el)), but no-one would seriously suggest that - I hope.

1 0

file suffixes
by Malcolm Wallace 30 Nov '00

30 Nov '00

I recall that at one point GHC came with "bundles", built in "ways", like profiling, parallel, tickyticky, etc.. There was also some filename-mangling scheme for distinguishing .hi interface and .o object files from the different bundles. My question is, what was that filename-mangling scheme? I ask because I'm about to do something similar for nhc98's "ways" (heap-profiling, time-profiling, tracing, etc.), and some consistency here might be useful. Regards, Malcolm

2 1

RE: ghc-4.xx Alpha port?
by Julian Seward (Intl Vendor) 30 Nov '00

30 Nov '00

| > Hi guys. Has anyone been so rash as to try this? Any indications | > as to the likely "degree of difficulty"? I'd have a go myself, but | > I'm rather busy with teaching. (Which is ironic, since teaching is | > what I want it for...) | | Degree of difficulty is likely to be less than a starting completely | non-existent port (eg. IA64), but still significant. The | 64-bitness is | likely to be more of an issue than the Alpha-specific stuff, though. Getting it working on Alphas would also be of benefit in the sense that it gets the 64-bitness working again. That gives one less thing to worry about when porting to IA64, if/when that should happen. J

1 0

RE: ghc-4.xx Alpha port?
by Simon Marlow 30 Nov '00

30 Nov '00

> Hi guys. Has anyone been so rash as to try this? Any indications > as to the likely "degree of difficulty"? I'd have a go myself, but > I'm rather busy with teaching. (Which is ironic, since teaching is > what I want it for...) Degree of difficulty is likely to be less than a starting completely non-existent port (eg. IA64), but still significant. The 64-bitness is likely to be more of an issue than the Alpha-specific stuff, though. If there's sufficient demand for a port I'll help out; I did have an account on the Compaq testdrive machines at one point (they have Alpha/Linux and Alpha/*BSD machines) which has probably expired now, but it's a good place to get some free Alpha cycles. Cheers, Simon

1 0

ghc-4.xx Alpha port?
by Alex Ferguson 30 Nov '00

30 Nov '00

Hi guys. Has anyone been so rash as to try this? Any indications as to the likely "degree of difficulty"? I'd have a go myself, but I'm rather busy with teaching. (Which is ironic, since teaching is what I want it for...) Cheers, Alex.

1 0

Exception Handling
by Smelly Pooh 28 Nov '00

28 Nov '00

I'm writing an application at the moment (in Haskell duh) and the issue of exception handling has come up. I don't want to use Maybe (because that would destructure the code somewhat) or any kind of Monad and I've settled on the idea of SPJs Exception extension. The idea is to create a data type with a different constructor per exception as in data MyException = Ex1 | Ex2 | Ex3 then use throwDyn/catchDyn to throw and catch it. Unfortunately this requires MyException to be an instance of class Typeable, and the documentation on that is quite sparse. Any advice or pointers would be greatly appreciated

2 1

New InstallShield: no more DLLs
by Reuben Thomas 27 Nov '00

27 Nov '00

I've put up a new InstallShield for GHC 4.08.1 (Windows edition). This no longer contains DLLs and import libraries for the libraries, so you have to use the compiler with -static. I intend to stick to this scheme in future releases (probably replacing -static with -dynamic), as GHC derives few benefits from DLLized libraries, and a lot of disadvantages. Also, there is at present an unresolved and deep-seated bug (possibly not even in GHC) that prevents some very simple DLLized programs from working. Users of DLLs need not despair: one important (and, to the best of my knowledge, fully working) version of DLL building remains: you can still build static DLLs, that is, DLLs in which all the code has been compiled statically, so that all the necessary library code is linked into the DLL. Hence, you can still build DLLs to be called from other languages, or to be wrapped up as COM components, or whatever. Finally, one nice side effect is that the size of the distribution is nearly halved: it now weighs in at a little over 12Mb. -- http://sc3d.org/rrt/ | violence, n. bravery for cowards

1 0

unsubscribe glasgow-haskell-users
by Wooseok Yang 25 Nov '00

25 Nov '00

unsubscribe glasgow-haskell-users

1 0

types from ghc - got them!
by Bernard James POPE 21 Nov '00

21 Nov '00

Hi again, For my previous example: main = putStr $ show (fred 1 3) where fred a b = let myid x = x in myid (plus a b) plus x y = x + y I can now get the following output: ==================== Bernie: All Binder TypeSigs ==================== main :: IO () plus :: forall a. (Num a) => a -> a -> a fred :: forall a. (Num a) => a -> a -> a myid :: forall t_aMv. t_aMv -> t_aMv Which is exactly what I want. Turned out to be quite simple in the end. Thanks a lot for all your help Simon. Just out of curiosity, do you think that this sort of output would be useful for other people? I don't know what your plans are for GHCi, but you may be considering a mode that prints types out, something like :t in hugs. I always found it frustrating in hugs that I couldn't get the types of locally defined values. My students also find this frustrating, and it sometimes causes them to avoid local definitions. Obviously there are issues with type variables which are quantified outside the local definition, but careful naming of things should be able to fix this. Regards, Bernie. Simon Peyton-Jones writes: > Bernie > > All (I think) the top level bindings come out of the type check > as an AbsBinds. This is where we generalise from a monomorphic > thing to a polymorphic thing. > > An AbsBinds has four components, the third of which is a list of > triples (TyVar, Id, Id). You want to grab the first of these Ids (only). > You can then ignore the MonoBinds inside the fourth component of > the AbsBinds. So your code will get quite a bit simpler. > > The two Ids in the triple are the polymorphic top-level binder and > the monomorphic (perhaps recursive) thing that it generalises. > It's a bit hard to explain in a short space. Look at the output of the > desugarer for a simple defn, to see what an AbsBinds translates to. > > Anyway these polymorphic Ids will have exactly the for-alls and > constraints that you want > > hope this gets you moving

2 1