[Haskell-cafe] ANN: WFLP 2010 Call for participation

2010-01-01 Thread Pablo Nogueira
Call For Participation WFLP2010 19th International Workshop on Functional and (Constraint) Logic Programming Madrid, Spain

[Haskell-cafe] Final CFP: WFLP 2010. Deadlines extended: Abstract due Nov 18; Full paper due Nov 25 (LNCS)

2009-11-13 Thread Pablo Nogueira
[Deadlines extended: Abstract due Nov 18; Full paper due Nov 25] Final Call For Papers 19th International Workshop on Functional and (Constraint) Logic Programming

[Haskell-cafe] ANN: WFLP2010 2nd CFP: LNCS + invited speaker + abstract due Nov 9

2009-10-27 Thread Pablo Nogueira
Second Call For Papers 19th International Workshop on Functional and (Constraint) Logic Programming Madrid, Spain, January 17, 2010 http://bab

[Haskell-cafe] ANN: WFLP 2010 Call for papers

2009-10-16 Thread Pablo Nogueira
[Apologies for multiple receptions of this message] Preliminary Call For Papers 19th International Workshop on Functional and (Constraint) Logic Programming Ma

Re: [Haskell-cafe] Using fundeps to resolve polymorphic types to concrete types

2008-07-30 Thread Pablo Nogueira
> [0] [EMAIL PROTECTED]:~/test $ ghc --version > The Glorious Glasgow Haskell Compilation System, version 6.8.2 I have an older version and wonder what goes wrong. Now that I think of it, other stuff that I coudn't compile might actually work in 6.8 It does make sense that |b| is resolved to |B| b

Re: [Haskell-cafe] Using fundeps to resolve polymorphic types to concrete types

2008-07-29 Thread Pablo Nogueira
>> But if you have actual values rather than just unit types, note that this >> won't work: >> >> > instance DeriveType A B where >> > someDestructor (SomeConstructor _ b) = b > > I couldn't understand the sentence "actual values rather than unit > types". What do you have in mind? I didn't

Re: [Haskell-cafe] Using fundeps to resolve polymorphic types to concrete types

2008-07-29 Thread Pablo Nogueira
Wren ng thornton wrote: > It compiles just fine with (DeriveType A b => b -> b) after all, which > resolves directly to (B -> B) That's not the case: simpleNarrow :: DeriveType A b => b -> b simpleNarrow = id Couldn't match expected type `b' (a rigid variable) against inferred type

Re: [Haskell-cafe] extensible data types in Haskell?

2008-07-08 Thread Pablo Nogueira
I prefer Bruno's approach, though. It allows meta-level type-checking of expressions and there's the possibility of closing the extension with a wrapper: (References: "Generics as a Library" and his PhD thesis) - GADT as a type class (or encode the type as it's fold): class Exp e where lit

Re: [Haskell-cafe] A type signature inferred by GHCi that is rejected when written explicitly

2008-07-08 Thread Pablo Nogueira
> I myselft don't understand why GHCi doesn't accept the type it > infered as an explicit signature ... I think it has to do with the following: Looking at the type errors, they seem to indicate that the type checker is being general and does not assume the |From| and |To| "relations" are betwe

[Haskell-cafe] A type signature inferred by GHCi that is rejected when written explicitly

2008-07-07 Thread Pablo Nogueira
I find this interesting, GHCi accepts a function |dmap| which I show below and infers its type, but if I annotate the function with the inferred type, GHCi's type-checker rejects it. I'm trying to generalise the datatype-generic dmap: < dmap :: Bifunctor s => (a -> b) -> Fix s a -> Fix s b < dma

Re: [Haskell-cafe] ANNOUNCE: Generic Haskell 1.80 (Emerald)

2008-04-14 Thread Pablo Nogueira
> This has certainly been taken into account when comparing approaches to > generic programming. I quote from page 18/19 from the work you and Bulat Indeed I was not aware of it. Missed that. Thanks for pointing it out! > Thus, full reflexivity of an approach is taken into account. This suggest

Re: [Haskell-cafe] ANNOUNCE: Generic Haskell 1.80 (Emerald)

2008-04-12 Thread Pablo Nogueira
On 12/04/2008, Thomas van Noort <[EMAIL PROTECTED]> wrote: > That's a good question. Unfortunately, only Haskell98 types are currently > supported by the Generic Haskell compiler. I thought constrained types were Haskell 98, but now I'm in doubt... > But at first sight, implementing support fo

Re: [Haskell-cafe] ANNOUNCE: Generic Haskell 1.80 (Emerald)

2008-04-12 Thread Pablo Nogueira
On 12/04/2008, Thomas van Noort <[EMAIL PROTECTED]> wrote: > Generic Haskell includes the following features: > > * type-indexed values -- generic functions that can be >instantiated on all Haskell data types. ^^^ I have perused the manual and wonder if parame

Re: [Haskell-cafe] foild function for expressions

2007-12-05 Thread Pablo Nogueira
I believe the exercise is about understanding folds. There are two references that are related to the exercise: A tutorial on the universality and expressiveness of fold, by Graham Hutton. Dealing with large bananas, by Ralf Lammel, etc. The last paper motivates well the need to gather all t

Re: [Haskell-cafe] Why is this strict in its arguments?

2007-12-05 Thread Pablo Nogueira
Hasn't Ryan raised an interesting point, though? Bottom is used to denote non-termination and run-time errors. Are they the same thing? To me, they're not. A non-terminating program has different behaviour from a failing program. When it comes to strictness, the concept is defined in a particular

Re: [Haskell-cafe] Rigid type-var unification failure in existentials used with parametrically polymorphic functions

2007-11-30 Thread Pablo Nogueira
> > mapBox :: forall a b. (a -> b) -> Box -> Box > > --:: forall a b. (a -> b) -> (exists a.a) -> (exists a.a) > > mapBox f (B x) = B (f x) > > > > However, at first sight |f| is polymorphic so it could be applied to > > any value, included the value hidden in |Box|. > > f is not polym

[Haskell-cafe] Re: Rigid type-var unification failure in existentials used with parametrically polymorphic functions

2007-11-30 Thread Pablo Nogueira
Stupid of me: > Isn't the code for mapBox :: forall a. (a -> a) -> Box -> Box > encoding the proof: > > Assume forall a. a -> a > Assume exists a.a > unpack the existential, x :: a = T for some T > apply f to x, we get (f x) :: a > pack into existential, B (f x) :: exists a.a > Disc

[Haskell-cafe] Rigid type-var unification failure in existentials used with parametrically polymorphic functions

2007-11-30 Thread Pablo Nogueira
A question about existential quantification: Given the existential type: data Box = forall a. B a in other words: -- data Box = B (exists a.a) -- B :: (exists a.a) -> Box I cannot type-check the function: mapBox :: forall a b. (a -> b) -> Box -> Box --:: forall a b. (a -> b)

Re: [Haskell-cafe] Pierce on type theory and category theory

2007-09-26 Thread Pablo Nogueira
Another opinion in case you need more: TAPL is excellent for self-study. There are solutions for most interesting exercises. And every type system presented comes with a downloadable implementation. You can practice with it and change it. Do not hesitate to get it. I also recommend Cardelli's pape

Re: [Haskell-cafe] Lack of expressiveness in kinds?

2007-03-16 Thread Pablo Nogueira
On 16/03/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: There is a wide-spread opinion that one ought not to give context to a data type declaration (please search for `restricted datatypes Haskell'). Someone said that in GHC typechecker such contexts called stupidctx. There has been a proposal

Re: [Haskell-cafe] GADTs: the plot thickens?

2007-01-31 Thread Pablo Nogueira
Aha, of course, Sorry, I misunderstood you. P. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Re: [Haskell-cafe] GADTs: the plot thickens?

2007-01-31 Thread Pablo Nogueira
Bruno, Now we modify thin to take an extra Nat n (not needed, but just to show the duality with thickening): I'm puzzled by the "not needed" bit. Isn't the introduction of Fin's indices reflected as values in the GADT , and the fact that the GADT makes that reflection, what makes it work? P

Fwd: [Haskell-cafe] GADTs: the plot thickens?

2007-01-31 Thread Pablo Nogueira
-- Forwarded message -- From: Pablo Nogueira <[EMAIL PROTECTED]> Date: 31-Jan-2007 12:04 Subject: Re: [Haskell-cafe] GADTs: the plot thickens? To: Conor McBride <[EMAIL PROTECTED]> I haven't tried this yet, but would declaring the class Nat be a starting po