On Wed, May 26, 2010 at 11:01 PM, Ben Lippmeier wrote:
>> While we can all acknowledge the technical impossibility of identifying the
>> original source language of a piece of code...
>
>
> Uh,
∀p (PieceOfCode(p) -> CanIdentifySourceLanguage(p))
is clearly false, while
∃p (PieceOfCode(p) -> Ca
On Thu, May 27, 2010 at 10:25 AM, Ionut G. Stan wrote:
> I was just wondering if there's any particular reason for which the two
> constructors of the Either data type are named Left and Right. I'm thinking
> that something like Success | Failure or Right | Wrong would have been a
> little better.
2010/5/27 Günther Schmidt :
> I'm exploring the use of church encodings of algebraic data types in
> Haskell.
> Since it's hard to imagine being the first to do so I wonder if folks here
> could point me to some references on the subject.
>
> I'm looking for examples of church encodings in Haskell
On Thu, May 27, 2010 at 9:11 PM, Stefan Monnier
wrote:
> I.e. to make such an encoding really usable, you need "deep
> polymorphism" (which GHC supports just fine, but which is not part of
> the Haskell standard).
Ah, yes, and thank you for pointing that out. My message involved a
great deal of h
On Tue, Jun 1, 2010 at 3:40 PM, Cory Knapp wrote:
>> In the new type, the parameter 'a' is misleading. It has no connection to
>> the
>> 'a's on the right of the equals sign. You might as well write:
>>
>> type CB = forall a. a -> a -> a
>>
> Ah! That makes sense. Which raises a new question: Is
On Fri, Jun 18, 2010 at 8:37 AM, Daniel Fischer
wrote:
>> Haven't you heard? Enough unit tests give you almost the same security
>> as a good static type system at the expense of more code!
>>
>> Uh, wait, why is that an advantage again? :p
>
> Duh, because it's much faster to develop in a dynami
On Sat, Jun 26, 2010 at 3:27 AM, Jason Dagit wrote:
> The types can depend on values. For example, have you ever notice we have
> families of functions in Haskell like zip, zip3, zip4, ..., and liftM,
> liftM2, ...?
> Each of them has a type that fits into a pattern, mainly the arity
> increases.
On Sat, Jun 26, 2010 at 6:55 PM, Erik de Castro Lopo
wrote:
> One problem with dependent types as I understand it is that type
> inference is not guaranteed to terminate.
Full type inference is undecidable in most interesting type systems
anyway. It's possible for the simply-typed λ-calculus, but
On Sat, Jul 3, 2010 at 4:28 PM, Dan Doel wrote:
> It's potentially not just a violation of intent, but of soundness. The
> following code doesn't actually work, but one could imagine it working:
>
> class C a b | a -> b
>
> instance C () a
>
> -- Theoretically works because C a b, C a c implies
On Sat, Jul 10, 2010 at 6:40 PM, Julian Fleischer
wrote:
> I guess I'm actually messing things up using the word "natural" - how can
> "expand the multiplication of zero with itself zero times" be natural?
How could it not be?
That is to say, what initial value would make sense for folding (*)
On Mon, Aug 9, 2010 at 3:42 PM, Job Vranish wrote:
> For monads like StateT, WriterT, ReaderT, the order doesn't matter (except
> perhaps for some pesky performance details). However, for monad transformers
> like ErrorT or ListT, the order _does_ matter.
Is it really correct to say that order do
On Mon, Aug 23, 2010 at 11:41 PM, wren ng thornton wrote:
> I believe the denotation of an iteratee is the transition function for an
> automaton (or rather a transducer). I hesitate to speculate on the specific
> kind of automaton without thinking about it, so maybe finite, maybe
> deterministic,
On Tue, Aug 24, 2010 at 11:44 AM, John Lato wrote:
>> Aren't they closer - in implementation and by supported operations -
>> to resumptions monads?
>>
>> See many papers by William Harrison here:
>> http://www.cs.missouri.edu/~harrisonwl/abstracts.html
>
> I'm not familiar with resumption monads.
On Tue, Aug 24, 2010 at 4:42 PM, Michael Vanier wrote:
> Adding OverlappingInstances to the language pragmas fixes the problem. My
> question is: why is this an overlapping instance? It would make sense if
> Int was an instance of Nat, but it isn't. Is this just a limitation in the
> way overla
On Fri, Aug 27, 2010 at 7:40 AM, Andrew Coppin
wrote:
> Unfortunately, I haven't found anything for Windows yet which has syntax
> hilighting for Haskell.
>
> I use SciTE, which has hilighting for a bazillion languages (including XML
> and JSON), but not Haskell sadly.
Veering somewhat offtopic,
On Fri, Aug 27, 2010 at 12:57 PM, Andrew Coppin
wrote:
> C. McCann wrote:
>>
>> On Fri, Aug 27, 2010 at 7:40 AM, Andrew Coppin
>> wrote:
>>
>>>
>>> Unfortunately, I haven't found anything for Windows yet which has syntax
>>> hilighting f
On Fri, Sep 3, 2010 at 11:47 AM, John Lato wrote:
> On Fri, Sep 3, 2010 at 1:29 PM, Ivan Lazar Miljenovic
> wrote:
>> On 3 September 2010 22:23, John Lato wrote:
>> > Do you have a kind * implementation of Foldable? I'd be interested in
>> > seeing it, because I was unable to create a usable i
On Wed, Sep 8, 2010 at 3:38 PM, Hector Guilarte wrote:
> If somebody can point out really good reasons on why I should use Haskell to
> do my work, please let me know them, they might help me convincing my
> bosses. On the other hand, if you believe Haskell is a bad language for this
> kind of tas
On Tue, Oct 12, 2010 at 8:56 AM, Uwe Schmidt wrote:
>> No, but there is no point in using a formalism that adds complexity
>> without adding functionality. Arrows are more awkward to use than
>> monads because they were intentionally designed to be less powerful than
>> monads in order to cover s
On Tue, Oct 12, 2010 at 3:00 PM, Paolo G. Giarrusso
wrote:
> Were you writing a paper, your comment would be fully valid. Here
> we're talking about a library for people to use in practice. In the
> middle, somebody should make sure that people without a PhD can learn
> arrows, by providing docume
On Wed, Oct 13, 2010 at 3:50 AM, Heinrich Apfelmus
wrote:
>> Combined with >>= / >> you have multiple reading direction in the same
>> expression, as in
>>
>> expression ( c . b . a ) `liftM` a1 >>= a2 >>= a3
>> reading order 6 5 4 1 2 3
>
> That's why I'm usually
On Fri, Oct 29, 2010 at 8:31 AM, Ben Millwood wrote:
> Besides, I'd think that often what Haskell developers lack is time
> more than skill - there are plenty of tasks that could be done without
> advanced knowledge of deep abstractions, if only someone could put
> aside a few weekends for them. F
On Thu, Oct 28, 2010 at 9:13 PM, Ivan Lazar Miljenovic
wrote:
> IIUC, [one of] the prime motivating factor[s] behind both reddit and
> StackOverflow is the accumulation of "karma", which leads to people
> posting just to try and accumulate karma even if they don't know what
> they're talking about
On Fri, Oct 29, 2010 at 6:13 PM, Ivan Lazar Miljenovic
wrote:
> So you'd prefer to have the discussion about a blog post be made
> distinct from the blog post itself? Why not keep them together, also
> so that people finding the blog post from someplace other than reddit
> (e.g. planet.haskell.or
On Fri, Oct 29, 2010 at 7:54 PM, wren ng thornton wrote:
> I'm sort of torn on this issue. On the one hand (#) has great potential as
> an operator, on the other hand I've found that having something like
> -XMagicHash (or TeX's \makeatletter and \makeatother) can be really helpful
> when you want
On Fri, Oct 29, 2010 at 10:30 PM, wren ng thornton wrote:
>> I suggest U+2621.
>
> I'm not sure I'd've ever recognized a funny 'z' as "caution sign"... :)
Well, I'm operating under the assumption that it's one of these:
http://en.wikipedia.org/wiki/Bourbaki_dangerous_bend_symbol
I would not be a
On Sat, Oct 30, 2010 at 11:34 AM, Ketil Malde wrote:
> Stack Overflow and Reddit are at least improvements over the traditional
> web forums, starting to acquire some of the features Usenet had twenty
> years ago. Much like Planet-style meta-blogs and RSS syndication makes
> it liveable to follow
On Tue, May 11, 2010 at 2:06 PM, John Meacham wrote:
> A better way might be
>
> class (Functor f, Functor g) => FunctorPair f g where
> transformFunctor :: f a -> g a
>
> though, I am not sure what your use is, there isn't an obvious instance
> to me, but I don't know what your motivating
On Fri, May 14, 2010 at 8:39 PM, Maciej Piechotka wrote:
> 1. Haskell Class/Type famillies/... are conceptually different then
> classes and interfaces.
I believe interfaces would be roughly equivalent to the subset of
single-parameter type classes such that:
- All type class methods are functi
On Thu, May 20, 2010 at 12:25 PM, Max Bolingbroke
wrote:
> "Available instances" are not a natural addition to this list. In
> particular, using that information can cause programs to become
> untypeable when the module or *any module it imports transitively*
> defines a new instance. This leads t
On Fri, May 21, 2010 at 12:30 PM, Jeremy Shaw wrote:
> Adding all the scoped type variable stuff does not seem to help. Alas,
> I can not figure out if this is a limitation of the type-checker, or
> something that is fundamentally impossible. Nor can I figure out how
> to work around the issue.
I
2010/5/23 Günther Schmidt :
> is there anybody currently using Haskell to construct or implement a query
> language?
I've a half-baked, type-indexed (in HList style) implementation of
relational algebra lying around somewhere, if that counts as a "query
language". I was experimenting with using it
2010/11/3 Petr Pudlak :
>> f = (\x -> x x) (\y -> y)
>> g = let x = \y -> y in x x
>
> The function "f" is not typable in the Hindley-Milner type system, while "g"
> is is (and its type is "a -> a"). The reason is that in the first case (f),
> the typing system tries to assign a single type to "x",
On Thu, Nov 11, 2010 at 10:53 AM, Ketil Malde wrote:
> ..and you are able to tell the difference. Am I wrong in thinking that
> this could be made to work if serialization was to/from an opaque type
> instead of (Byte)String, so that the *only* operations would be
> serialization and deserializat
Oops, forgot to send this to the list... sorry, Sjoerd.
On Thu, Nov 11, 2010 at 11:54 AM, Sjoerd Visscher wrote:
>> You would lose many uses of equational reasoning in your programs. Have you
>> every substituted 'x * 2' for the expression 'x + x' in one of your programs,
>> or vice versa? You ca
On Thu, Nov 11, 2010 at 1:57 PM, Stephen Tetley
wrote:
> On 11 November 2010 18:01, C. McCann wrote:
>
>> For instance, assuming serialize can be applied to functions of any
>> type, it would probably be trivial to write a function (isExpr :: a ->
>> Bool) that report
On Thu, Nov 11, 2010 at 3:30 PM, Stephen Tetley
wrote:
> The conclusion notes in passing that OCaml's persistence isn't
> referentially transparent. If the Haskell version wasn't, I'd expect a
> mea culpa from the authors at this point.
>From a quick glance at the paper, the Haskell version is re
On Fri, Nov 12, 2010 at 4:24 AM, Ketil Malde wrote:
> IMO, it's morally different, you're now operating on a file, and you
> shouldn't rely on the contents being predictable. You can make the
> sin-bin argument that IO can do anything, but I think there's a moral
> distinction between
>
> serial
On Mon, Nov 15, 2010 at 12:43 PM, Ling Yang wrote:
> Specifically: There are some DSLs that can be largely expressed as monads,
> that inherently play nicely with expressions on non-monadic values.
> We'd like to use the functions that already work on the non-monadic
> values for monadic values wi
On Sun, Nov 7, 2010 at 7:40 PM, Mitar wrote:
> I have a class Neuron which has (among others) two functions: attach
> and deattach. I would like to make a way to call a list/stack/bunch of
> attach functions in a way that if any of those fail (by exception),
> deattach for previously already attac
On Mon, Dec 6, 2010 at 2:33 AM, David Virebayre
wrote:
> Level 5
>
> I'm out of layers here. I think this is all there is to it.
Level 5 is after you've spent way too much time writing questions
and/or answers that people like and have over 10k "reputation". This
unlocks some basic moderation too
On Wed, Dec 8, 2010 at 5:41 AM, Ketil Malde wrote:
> I'm a bit surprised to find that there seems to be a lot of opposition
> to this view, but perhaps the existing structure is more secure than I
> thought?
The difference is in the ability to influence other packages and
metadata, I think. You c
On Thu, Dec 23, 2010 at 5:25 PM, Stephen Tetley
wrote:
> On 23 December 2010 21:43, Mario Blažević wrote:
>> Why are Cofunctor and Comonad classes not a part of the base library?
> [SNIP]
>> Later on I found that this question has been raised before by Conal Elliott,
>> nearly four years ago.
>>
On Thu, Dec 23, 2010 at 11:46 PM, Mario Blažević wrote:
>
> I don't personally care what's it called, as long as it's available. Can
> anybody point to an authoritative source for the terminology, though?
> Wikipedia claims that cofunctor is a contravariant functor.
Does nLab count as sufficientl
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