On Thu, Dec 23, 2010 at 5:25 PM, Stephen Tetley
stephen.tet...@gmail.com wrote:
On 23 December 2010 21:43, Mario Blažević mblaze...@stilo.com 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
On Thu, Dec 23, 2010 at 11:46 PM, Mario Blažević mblaze...@stilo.com 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
On Wed, Dec 8, 2010 at 5:41 AM, Ketil Malde ke...@malde.org 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
On Mon, Dec 6, 2010 at 2:33 AM, David Virebayre
dav.vire+hask...@gmail.com 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
On Mon, Nov 15, 2010 at 12:43 PM, Ling Yang ly...@cs.stanford.edu 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
On Sun, Nov 7, 2010 at 7:40 PM, Mitar mmi...@gmail.com 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
On Fri, Nov 12, 2010 at 4:24 AM, Ketil Malde ke...@malde.org 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
On Thu, Nov 11, 2010 at 10:53 AM, Ketil Malde ke...@malde.org 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
Oops, forgot to send this to the list... sorry, Sjoerd.
On Thu, Nov 11, 2010 at 11:54 AM, Sjoerd Visscher sjo...@w3future.com 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
On Thu, Nov 11, 2010 at 1:57 PM, Stephen Tetley
stephen.tet...@gmail.com wrote:
On 11 November 2010 18:01, C. McCann c...@uptoisomorphism.net 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
On Thu, Nov 11, 2010 at 3:30 PM, Stephen Tetley
stephen.tet...@gmail.com 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
2010/11/3 Petr Pudlak d...@pudlak.name:
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 Sat, Oct 30, 2010 at 11:34 AM, Ketil Malde ke...@malde.org 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
On Fri, Oct 29, 2010 at 8:31 AM, Ben Millwood hask...@benmachine.co.uk 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
On Thu, Oct 28, 2010 at 9:13 PM, Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com 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
On Fri, Oct 29, 2010 at 6:13 PM, Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com 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
On Fri, Oct 29, 2010 at 7:54 PM, wren ng thornton w...@freegeek.org 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
On Fri, Oct 29, 2010 at 10:30 PM, wren ng thornton w...@freegeek.org 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
On Wed, Oct 13, 2010 at 3:50 AM, Heinrich Apfelmus
apfel...@quantentunnel.de 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
On Tue, Oct 12, 2010 at 8:56 AM, Uwe Schmidt u...@fh-wedel.de 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
On Tue, Oct 12, 2010 at 3:00 PM, Paolo G. Giarrusso
p.giarru...@gmail.com 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,
On Wed, Sep 8, 2010 at 3:38 PM, Hector Guilarte hector...@gmail.com 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
On Fri, Sep 3, 2010 at 11:47 AM, John Lato jwl...@gmail.com wrote:
On Fri, Sep 3, 2010 at 1:29 PM, Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com wrote:
On 3 September 2010 22:23, John Lato jwl...@gmail.com wrote:
Do you have a kind * implementation of Foldable? I'd be interested in
On Fri, Aug 27, 2010 at 7:40 AM, Andrew Coppin
andrewcop...@btinternet.com 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.
On Fri, Aug 27, 2010 at 12:57 PM, Andrew Coppin
andrewcop...@btinternet.com wrote:
C. McCann wrote:
On Fri, Aug 27, 2010 at 7:40 AM, Andrew Coppin
andrewcop...@btinternet.com wrote:
Unfortunately, I haven't found anything for Windows yet which has syntax
hilighting for Haskell.
I use
On Mon, Aug 23, 2010 at 11:41 PM, wren ng thornton w...@freegeek.org 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
On Tue, Aug 24, 2010 at 11:44 AM, John Lato jwl...@gmail.com 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
On Tue, Aug 24, 2010 at 4:42 PM, Michael Vanier mvanie...@gmail.com 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
On Mon, Aug 9, 2010 at 3:42 PM, Job Vranish job.vran...@gmail.com 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
On Sat, Jul 10, 2010 at 6:40 PM, Julian Fleischer
julian.fleisc...@fu-berlin.de 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
On Sat, Jul 3, 2010 at 4:28 PM, Dan Doel dan.d...@gmail.com 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
On Sat, Jun 26, 2010 at 3:27 AM, Jason Dagit da...@codersbase.com 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
On Sat, Jun 26, 2010 at 6:55 PM, Erik de Castro Lopo
mle...@mega-nerd.com 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
On Fri, Jun 18, 2010 at 8:37 AM, Daniel Fischer
daniel.is.fisc...@web.de 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
On Tue, Jun 1, 2010 at 3:40 PM, Cory Knapp cory.m.kn...@gmail.com 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
On Thu, May 27, 2010 at 10:25 AM, Ionut G. Stan ionut.g.s...@gmail.com 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
2010/5/27 Günther Schmidt gue.schm...@web.de:
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
On Thu, May 27, 2010 at 9:11 PM, Stefan Monnier
monn...@iro.umontreal.ca 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
On Wed, May 26, 2010 at 11:01 PM, Ben Lippmeier b...@ouroborus.net 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
2010/5/23 Günther Schmidt gue.schm...@web.de:
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
On Fri, May 21, 2010 at 12:30 PM, Jeremy Shaw jer...@n-heptane.com 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
On Thu, May 20, 2010 at 12:25 PM, Max Bolingbroke
batterseapo...@hotmail.com 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
On Fri, May 14, 2010 at 8:39 PM, Maciej Piechotka uzytkown...@gmail.com 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
On Tue, May 11, 2010 at 2:06 PM, John Meacham j...@repetae.net 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
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