Hi Nicolas,
It's not intentional, but Iavor is aware of this, and we want to change it.
I'm CC-ing him as he might know more about what the current plan is.
Cheers,
Pedro
On Sat, Aug 24, 2013 at 3:20 PM, Nicolas Trangez nico...@incubaid.comwrote:
Hello Cafe,
I was playing around with
Hi,
On Fri, Jul 26, 2013 at 10:42 PM, Wvv vite...@rambler.ru wrote:
First useful use is in Typeable.
In GHC 7.8
class Typeable (a::k) where ... == class Typeable (a ::**) where ...
But we can't write
data Foo (a::k)-(a::k)-* ... deriving Typeable
Why not? This works fine in 7.7, as far
Hi,
On Wed, Jun 5, 2013 at 11:21 PM, TP paratribulati...@free.fr wrote:
José Pedro Magalhães wrote:
Oh, it should probably be simply
deriving instance Typeable 'Zero
deriving instance Typeable 'Succ
Yes, that's how it should be. Please let me know if that
doesn't work
On Wed, Jun 5, 2013 at 8:46 AM, Roman Cheplyaka r...@ro-che.info wrote:
* TP paratribulati...@free.fr [2013-06-05 00:37:36+0200]
Roman Cheplyaka wrote:
Try adding
deriving instance Typeable 'Zero
deriving instance Typeable a = Typeable ('Succ a)
to your module.
(I
What is the error that you get?
Cheers,
Pedro
On Tue, Apr 16, 2013 at 8:07 PM, Anatoly Yakovenko aeyakove...@gmail.comwrote:
-- ok, something in deriving NFData using Generics in a type that has a
Vector in it.
{-# LANGUAGE DeriveGeneric #-}
import Control.DeepSeq
import System.IO
Hi Luke,
Even though you might have made up your mind already, here's some more
info. If you want a
zipper that does not use Typeable (and thus runtime type comparison and
casting, which are
potentially inefficient), you can use the zipper in Multirec [1].
Creating a zipper based on GHC.Generics
Hi,
Actually, if you really want folds, you should use regular [1] instead.
Here's an example of
a generic fold using regular:
-- Datatype representing logical expressions
data Logic = Var String
| Logic :-: Logic -- implication
| Logic :-: Logic -- equivalence
On Mon, Mar 18, 2013 at 9:56 AM, Christopher Done chrisd...@gmail.comwrote:
As a follow up, here's an implementation: http://haskellnews.org/
Could it have an RSS feed?
Thanks,
Pedro
More info here:
http://www.reddit.com/r/haskell/comments/1ahgrn/haskell_news/c8xfp9s
On 10 February
Hi Roman,
Yes, the automatic derivation of Generic instances does not see through
newtypes.
Cheers,
Pedro
On Sun, Jan 27, 2013 at 8:17 PM, Roman Cheplyaka r...@ro-che.info wrote:
Hi,
Is it possible to generate different instances for newtypes and
datatypes using GHC.Generics?
Roman
clear. What I want is somehow to find out whether the
type under consideration is declared using data or newtype.
Is it possible?
Roman
* José Pedro Magalhães j...@cs.uu.nl [2013-01-27 20:29:52+]
Hi Roman,
Yes, the automatic derivation of Generic instances does not see through
Won't it derive it with StandaloneDeriving?
Cheers,
Pedro
On Tue, Jan 22, 2013 at 1:28 PM, Roman Cheplyaka r...@ro-che.info wrote:
I need to declare a Typeable instance for a type which has an argument
of kind * - *. GHC refuses to derive it.
What is a recommended way to go about it?
In
Yes, that will work. But soon we'll have poly-kinded Typeable in HEAD,
which will be able to derive that instance.
Cheers,
Pedro
On Tue, Jan 22, 2013 at 2:34 PM, Roman Cheplyaka r...@ro-che.info wrote:
I just found mkTyCon3 which generates the fingerprint automatically.
(I was looking at
Hi all,
Thanks for all the feedback and kind words. Yes, we're planning to have
export to PDF/midi
options soon. We have plenty of ideas, but limited time :-/
User feedback is collected (and voted for) on
https://chordify.uservoice.com/
Thanks,
Pedro
On Fri, Jan 18, 2013 at 12:37 PM, Rustom
at this stage, so if you're interested in music
and could use an automatic chord transcription service, please try Chordify!
Cheers,
Pedro
[1] http://chordify.net/
[2] http://hackage.haskell.org/package/HarmTrace
[3] José Pedro Magalhães and W. Bas de Haas. Functional Modelling of
Musical Harmony
Hi Ravi,
You might want to browse through Comparing Libraries for Generic
Programming in Haskell:
http://www.cs.uu.nl/research/techreps/repo/CS-2008/2008-010.pdf
SYB and Uniplate are two widely used and well-maintained systems for
strategic traversals over arbitrary datatypes. There are other
Hi Johan,
The error message is not ideal, but it does say that adding a Generic (Foo
a)
instance might solve the problem.
I generally do not export classes like GHashable because they are closed;
users
should never need to provide more instances themselves. Also, exporting the
class
won't make
Hi Takayuki,
Just thought I'd mention another approach to a variadic zipWith, this one
using type families:
http://typesandkinds.wordpress.com/2012/11/26/variable-arity-zipwith/
The current lack of overlap in type families makes things a bit more
complicated, but it can
be solved using the
+1
Pedro
On Sun, Oct 28, 2012 at 12:20 AM, Niklas Hambüchen m...@nh2.me wrote:
(I have mentioned this several times on #haskell, but nothing has
happened so far.)
Are you aware that all haskell.org websites (hackage, HaskellWiki, ghc
trac) allow unencrypted http connections only?
This
Hi,
Please use GHC 7.6 for experimenting with PolyKinds/DataKinds; the
implementation in 7.4 was not fully complete. Your code compiles fine in
7.6.
Cheers,
Pedro
On Fri, Oct 26, 2012 at 3:10 AM, Ahn, Ki Yung kya...@gmail.com wrote:
Promotion works for user defined lists such as
data List
Hi all,
Consider the following program:
module Test where
import System.Process (readProcess)
main :: IO ()
main = readProcess git [describe, --tags] = putStr
In Windows I get the following behaviour:
git --version
git version 1.7.10.msysgit.1
ghc --version
The Glorious Glasgow
echo %PATH%` it shows me the expected %PATH%, including
the directory
where the git binary lives.
Thanks,
Pedro
On Thu, Oct 25, 2012 at 10:05 PM, José Pedro Magalhães j...@cs.uu.nlwrote:
Hi all,
Consider the following program:
module Test where
import System.Process (readProcess)
main
Hi Paul,
On Thu, Oct 25, 2012 at 4:22 PM, Paul Visschers m...@paulvisschers.netwrote:
Hello everyone,
I've been playing around with the data kinds extension to implement
vectors that have a known length at compile time. Some simple code to
illustrate:
{-# LANGUAGE DataKinds, GADTs,
Hi Florian,
Will this do?
class Tc a where
tc :: Exp - Maybe (Term a)
instance Tc Int where
tc (Lit i) = return (TLit i)
tc (Succ i) = tc i = return . TSucc
tc (IsZero i) = Nothing
tc e= tcIf e
instance Tc Bool where
tc (Lit i) = Nothing
tc (Succ i)
Nope, but it should work on 7.6 (also on the release candidate).
The 'X' should be lowercase, though, like type variables.
Cheers,
Pedro
On Wed, Aug 22, 2012 at 12:01 AM, dude d...@methodeutic.com wrote:
Hello All:
I'm working through Giving Haskell a Promotion.
Section 2.4 presents an
On Tue, Jun 19, 2012 at 4:04 PM, Jacques Carette care...@mcmaster.cawrote:
User beware: this is gencheck-0.1, there are still a few rough edges. We
plan to add a Template Haskell feature to this which should make deriving
enumerators automatic for version 0.2.
Can you provide me a quick
Hi,
This has been discussed before:
http://haskell.1045720.n5.nabble.com/Data-Kinds-and-superfluous-in-my-opinion-constraints-contexts-td5689436.html
Feel free to open a feature request for this. I think it's something we
should consider
addressing, but at the moment it's not immediately clear
Hi Philip,
On Fri, May 11, 2012 at 5:12 PM, Philip K. F. Hölzenspies
p...@st-andrews.ac.uk wrote:
However, it turns out that this never leads to an evaluation of
extTyNamesLoc. I've come as far as to see that, since Located a is a
synonym for GenLocated SrcSpan a, the type we're looking for
Hi Romildo,
I had a quick look at your code. In general it seems fine, although I
haven't tested it. You might want to use HLint to give you coding tips.
I don't understand your remark about wanting the type checker to produce
an expression annotated with both positions and calculated types.
Hi Romildo,
If I understand correctly, you now want to add annotations to
mutually-recursive datatypes. The annotations package supports that.
Section 8 of our paper [1] gives an example of how to do that, and also
Chapter 6 of Martijn's MSc thesis [2].
Let me know if these references do not
Hi,
On Wed, Mar 14, 2012 at 07:54, Johan Holmquist holmi...@gmail.com wrote:
I guess you want an automatically derived show that indents, but if
you don't mind defining you own, Data.PrettyPrint is really nice.
Though most likely any form of pretty-printing will be generic, and can be
Hi Reiner,
It is indeed not strictly necessary to define such helper classes for kind
* generic functions. You do need them for kind * - * functions, though.
Also, I think they should always be used because they help keep things
separate. If we use an implementation of generics with DataKinds
Hi Yves,
GHC.Generics [1] and SYB [2] are two rather different approaches to generic
programming. There are things that can be done in one but not in the other,
and there are things that are easier on one rather than the other. For
instance, SYB tends to be very useful for large AST
Data have been used for generic Deriving of classes? I
imagine it would have been harder, but I fail to see if would have been
possible...
Le 12 mars 2012 16:58, José Pedro Magalhães j...@cs.uu.nl a écrit :
Hi Yves,
GHC.Generics [1] and SYB [2] are two rather different approaches to
generic
2012/2/25 Andres Löh andres.l...@googlemail.com
Would you have an example of a type for which it would be useful to have
a DeepSeq instance, and that would require a V1 instance? I cannot think
of one now; I originaly thought it would be necessary to permit deriving
DeepSeq instances for
2012/2/24 Maxime Henrion mhenr...@gmail.com
On Fri, 2012-02-24 at 07:49 +0100, Jos Pedro Magalhes wrote:
Hi,
2012/2/23 Maxime Henrion mhenr...@gmail.com
* Why do you have the instance:
instance GDeepSeq V1 where grnf _ = ()
The only
Hi Andres,
2012/2/24 Andres Löh andres.l...@googlemail.com
I don't understand what's going on here. Instances for V1 should of
course be defined if they can be! And in this case, a V1 instance
makes sense and should be defined. The definition itself doesn't
matter, as it'll never be
Hi,
2012/2/23 Maxime Henrion mhenr...@gmail.com
* Why do you have the instance:
instance GDeepSeq V1 where grnf _ = ()
The only way to construct values of a void type is using ⊥. And I
would expect that rnf ⊥ = ⊥, not (). I think the best thing is to just
remove the V1 instance.
Hi,
2012/2/19 Bas van Dijk v.dijk@gmail.com
I do think it's better to integrate this into the deepseq package (and
thus removing the default implementation of rnf). Otherwise we end up
with two ways of evaluating values to normal form.
I agree with this, and I guess many people are
Hi,
This is a change in behavior. Previously GHC was more liberal than Haskell
98 prescribed, and would not default the kind of otherwise unconstrained
type variables to *. 7.4 does default to *, so you have to provide kind
signatures when you want another kind (particularly in phantom type
Yes
On Wed, Nov 23, 2011 at 19:11, heathmatlock heathmatl...@gmail.com wrote:
Question: Do you want a mascot?
Answers:
Yes
No
--
This is an attempt to figure out if this idea is going anywhere.
___
Haskell-Cafe mailing list
In general, I like the idea of having a mascot, and think that something
along these lines will be great.
Cheers,
Pedro
On Wed, Nov 16, 2011 at 01:01, heathmatlock heathmatl...@gmail.com wrote:
I liked Go's mascot, and I figure it couldn't hurt to have our own. I
spent the past hour making
Hi,
I'm not sure I understand your question. But if you mean that you want to
retrieve the type variable names, as they were defined in the source, then
I can tell you that the generic deriving mechanism cannot do this.
Cheers,
Pedro
On Sun, Nov 6, 2011 at 14:35, Magicloud Magiclouds
(GHC.Generics.Par0
a_adY)))
Still not perfect, in that the representation type should really appear as
a type instance inside the Generic instance, but at least all the important
information is printed.
Cheers,
Pedro
2011/11/3 Bas van Dijk v.dijk@gmail.com
2011/11/3 José Pedro Magalhães j...@cs.uu.nl
2011/11/4 Bas van Dijk v.dijk@gmail.com
Thanks José!
Will this make it into ghc-7.4?
Yes, I think so.
Cheers,
Pedro
Bas
2011/11/4 José Pedro Magalhães j...@cs.uu.nl:
Hi,
Now, for the following datatype:
data X a = X { myX :: a } deriving Generic
You get the following
Thanks, you spotted another mistake on that page, I corrected it.
Make sure to have a look at the functions in
http://hackage.haskell.org/package/generic-deriving too; I'm sure those
compile :-)
Pedro
2011/11/3 Magicloud Magiclouds magicloud.magiclo...@gmail.com
2011/11/1 José Pedro
Hi Bas,
First of all, thanks for these numbers. I have previously compared the
performance of GP libs [1] and your results confirm what I would expect,
except for that last one, BigSum/fromJSON/generic.
It's good that you're using INLINE pragmas on the generic function already.
What I would also
-ddump-deriv will print (most of) it.
Cheers,
Pedro
On Thu, Nov 3, 2011 at 16:26, Magicloud Magiclouds
magicloud.magiclo...@gmail.com wrote:
Hi,
I am learning the new generic feature of ghc. I'd have to say, it is
harder than template to enter.
When I started to learn template, ghc
Hi,
2011/11/3 Bas van Dijk v.dijk@gmail.com
2011/11/3 José Pedro Magalhães j...@cs.uu.nl:
-ddump-deriv will print (most of) it.
But it doesn't print the most useful piece of information: the
definition of Rep.
Yes... I am aware of this.
It would be great if this could be added
Oh, right, I see that some things on that page need updating; I'll do so.
Thanks,
Pedro
On Tue, Nov 1, 2011 at 09:33, Magicloud Magiclouds
magicloud.magiclo...@gmail.com wrote:
On Tue, Nov 1, 2011 at 1:59 PM, Andres Löh andres.l...@googlemail.com
wrote:
Hi.
I do not know why, my ghc
On Tue, Nov 1, 2011 at 09:43, Conrad Parker con...@metadecks.org wrote:
On 1 November 2011 03:43, Alexander Kjeldaas
alexander.kjeld...@gmail.com wrote:
On 31 October 2011 17:22, Yitzchak Gale g...@sefer.org wrote:
Gregory Crosswhite wrote:
could [Hackage] have a feature where when a
Hi Rusi,
GHC has built-in support for two generic programming libraries. SYB [1]
support has been there for a long time. The new generic mechanism [2], which
allows you to define your own, (almost) derivable classes, only appeared in
7.2, but is planned to stay.
What library you should use
Hi Karel,
You can use SYB's toConstr/dataTypeOf [1] to obtain information about the
name of the constructor and datatype. Alternatively, you can also use the
new generic programming framework of ghc-7.2 [2].
Cheers,
Pedro
[1]
Hi,
I'm not sure I fully understand what you're trying to do, but when I read
Ideally, I'd like to restrict my
search to Located instances that wrap an instance of Outputable,
I think this means SYB is not the right tool. Due to the way Typeable works
(it's monomorphic), SYB doesn't really
describe the issue in more detail in the paper:
José Pedro Magalhães and Johan Jeuring. Generic Programming for Indexed
Datatypes.
Color pdf: http://dreixel.net/research/pdf/gpid.pdf
Greyscale pdf: http://dreixel.net/research/pdf/gpid_nocolor.pdf
Cheers,
Pedro
Many thanks in advance,
Tim
Hi Ari,
I won't really try to answer your question, but I'll give you the code for
gzipWithQ written by Alexey Rodriguez Yakushev some years ago for his
comparison on generic programming libraries. The original darcs repo no
longer exists, but here is the file which I think is relevant for you:
Hi all,
What causes the following build failure on Hackage?
*** setup configure
Configuring instant-generics-0.3.2...
cabal-setup: At least the following dependencies are missing:
syb 0.4
This is in package
Hi all,
I want to use cabal-install on a machine without internet access. I tried
downloading http://hackage.haskell.org/cgi-bin/hackage-scripts/archive.tar,
unpacking it and setting the local-repo field in the config file to this
location but that doesn't work, as cabal-install says that it is
,
Pedro
2011/4/7 Yitzchak Gale g...@sefer.org
José Pedro Magalhães wrote:
I want to use cabal-install on a machine without internet access.
Work is ongoing for a version of hackage that you can just
install on your own server. Perhaps the people working on that
can comment about the status
Yes, I have that tarball. I just don't know how to tell cabal-install to use
it. Going to each package, individually unpacking and installing it is what
I've been doing so far, but I was hoping that could be automated.
Cheers,
Pedro
On Thu, Apr 7, 2011 at 14:18, Magnus Therning
to use a tool like process explorer [1] to see
which specific dlls are getting loaded when you run.
Ryan
[1] http://technet.microsoft.com/en-us/sysinternals/bb896653
2011/3/15 José Pedro Magalhães j...@cs.uu.nl
Hi all,
I'd just like to add that I succeeded in building gtk2hs in Windows XP
Hi all,
I'd just like to add that I succeeded in building gtk2hs in Windows XP 64bit
with GHC 7.0.2, using the 2.16 bundle from [1] and following the
instructions in [2].
However, running the test program of [2] still fails at runtime with The
procedure entry point g_assertion_message_expr could
Hi all,
I've played a bit with Intel's Manycore Testing Lab (
http://software.intel.com/en-us/articles/intel-many-core-testing-lab/). Part
of the agreement to use it requires that you report back your experiences,
which I did in an Intel forum post (
(Forwarding to haskell-cafe)
Hi,
I have a program that computes a matrix of Floats of m rows by n columns.
Computing each Float is relatively expensive. Each line is completely
independent of the others, so I thought I'd try some simple SMP parallelism
on this code:
myFun :: FilePath - IO ()
Hello all,
I kept being annoyed at the fact that Windows doesn't come with anything
similar to the unix time utility, so I created a small Haskell program
that does something similar. I thought this could perhaps be useful to
others, so it's now available on Hackage:
Hello,
2011/2/15 Simon Peyton-Jones simo...@microsoft.com
but currently any pragmas in a class decl are treated as attaching to the
*default method*, not to the method selector:
Thanks for this clarification, I had wondered about this for a while. I
think it would also be nice to mention
Hi,
I don't think you can do that, since `ext` relies on Typeable and Typeable
only works for monomorphic types.
Cheers,
Pedro
On Wed, Feb 2, 2011 at 20:31, Sugar Bzzz sugarbz...@gmail.com wrote:
Dear -cafe,
Is it possible to extend a generic reader (extR / ext1R from syb) with a
type
Hi Henk-Jan,
On Mon, Aug 23, 2010 at 00:15, Henk-Jan van Tuyl hjgt...@chello.nl wrote:
L.S.,
I am trying to compile the current release of UHC (1.0.1); I started with
the installation of the most recent version of uulib and uuagc. When
running
make uhc
I received the following message:
Hi Romildo,
2010/7/23 José Romildo Malaquias j.romi...@gmail.com
On Tue, Jul 20, 2010 at 09:17:15AM +0200, José Pedro Magalhães wrote:
2010/7/19 José Romildo Malaquias j.romi...@gmail.com
I am writing here to ask suggestions on how to annotate an ast with
types (or any other
Hi Oleg,
On Wed, Jul 21, 2010 at 09:36, o...@okmij.org wrote:
Jose Pedro Magalhaes wrote:
From what I understand, you are using a list of integers to encode a path
to
a subterm. This is a practical and lightweight implementation, but less
type-safe: it is easy to encode annotations that
have type annotations, but declarations can not.
Comments?
Indeed I would suggest the method described in our paper:
Martijn van Steenbergen, José Pedro Magalhães, and Johan Jeuring. Generic
selections of subexpressions.
Paper link: http://dreixel.net/research/pdf/gss_draft.pdf
Related hackage
Hi Oleg,
From what I understand, you are using a list of integers to encode a path to
a subterm. This is a practical and lightweight implementation, but less
type-safe: it is easy to encode annotations that do not correspond to any
value. Also, it cannot guarantee, with types alone, that every
Hi Oscar,
On Sat, May 15, 2010 at 22:19, Oscar Finnsson oscar.finns...@gmail.comwrote:
(...)
I guess my questions are:
1. Is it possible to combine GADTs with Scrap your Boilerplate?
Your GADT encodes an existential datatype. The closest attempt to encode
existential types in (something
Hi Ozgur,
At least template-haskell-2.4.0.0 (which comes with GHC 6.12) has syntax for
type equality constraints [1], so I'm guessing it should support GADTs (I
haven't actually tested it). It also has syntax for type families.
Cheers,
Pedro
[1]
Hi,
On Thu, Apr 15, 2010 at 14:40, Johannes Waldmann
waldm...@imn.htwk-leipzig.de wrote:
What happened was this:
1. add some modules to a library (but forget to mention them in the cabal
file),
then (in the lib source dir, without cleaning/reconfiguring)
cabal install --global (runs
A few days ago I changed the links from the SYB wiki [1] to point to an
archived version of the vu.nl webpage:
http://web.archive.org/web/20080622204226/http://www.cs.vu.nl/boilerplate/
But it would be nice to have the webpage up again, somewhere.
Cheers,
Pedro
[1]
Hi Jeremy,
As Neil Mitchell said before, if you really don't want to expose the
internals of Text (by just using a derived instance) then you have no other
alternative than to use String conversion. If you've been using it already
and performance is not a big problem, then I guess it's ok.
Hello Paul,
On Fri, Dec 18, 2009 at 16:47, Paul Keir pk...@dcs.gla.ac.uk wrote:
(...)
I'm enjoying using SYB, and had hoped to use only functions from the
package,
but couldn't find a way; and this does the job for now. I've also seen that
there are many other approaches to generic
Hello,
The release of the regular library for generic programming on Hackage
[1] also contains a form of deep seq [2]. This means that you don't
even have to write the definition of 'deepseq', you can just use
'gdseq' (assuming you have used Template Haskell to derive the generic
representations
Hi,
While I agree that the documentation of Data.Generics is not perfect, I do
not think it is possible to have the haddock documentation be
self-contained. For a thorough understanding of syb, a user has to read the
two initial papers, which are linked from the haddock documentation. I also
do
Hi Dimitry,
On Thu, Oct 1, 2009 at 05:23, Dimitry Golubovsky golubov...@gmail.comwrote:
OK, I got it to work with gread/gshow.
However I have noticed this:
*Main (gread $ gshow $ FuncExpr 0 [] (EmptyStmt 0)) :: [(Expression
Int, String)]
[(FuncExpr 0 [] (EmptyStmt 0),)]
vs.
*Main
Hey Andy,
On Thu, Sep 17, 2009 at 15:40, Andy Gimblett hask...@gimbo.org.uk wrote:
Now, some of those algebraic data type types happen to be
enumerations; in this case, my idea is to list the constructors, with
the rule that each constructor's position in the list is the Int which
gets
Hello,
On Thu, Sep 17, 2009 at 16:05, Daniel Fischer daniel.is.fisc...@web.dewrote:
Am Donnerstag 17 September 2009 15:56:03 schrieb José Pedro Magalhães:
Hey Andy,
On Thu, Sep 17, 2009 at 15:40, Andy Gimblett hask...@gimbo.org.uk
wrote:
Now, some of those algebraic data type types
Hi Dimitry,
I think what you want is stand-alone deriving:
http://www.haskell.org/ghc/docs/latest/html/users_guide/deriving.html#stand-alone-deriving
Cheers,
Pedro
On Fri, Sep 11, 2009 at 16:29, Dimitry Golubovsky golubov...@gmail.comwrote:
Hi,
Given a datatype defined somewhere in a
Hello Louis,
On Tue, Sep 8, 2009 at 19:06, Louis Wasserman wasserman.lo...@gmail.comwrote:
Sean,
The answer is, I'm working on a recently semi-released package called
TrieMap.
Is that similar to what is done in [1]? A draft paper [2] also refers that
implementation.
Cheers,
Pedro
[1]
Hello,
On Thu, Aug 20, 2009 at 16:54, Max Desyatov explicitc...@googlemail.comwrote:
Sean Leather leat...@cs.uu.nl writes:
I'm not sure the problem you're running into is strictly a generic
programming (GP) one. Typically, GP takes code that is often written
and generalizes it, so that
Hello Henry,
The paper A Lightweight Approach To Datatype-Generic Rewriting [1]
describes a way to generically add a constructor to any regular datatype
using type-indexed datatypes [2]. A similar technique could be used to add a
new field to each constructor. Then you get something like:
data
Hey David,
For instance:
arity :: (Data a) = a - Int
arity = length . gmapQ (const ())
Cheers,
Pedro
On Thu, Jun 25, 2009 at 17:31, David Fox dds...@gmail.com wrote:
Is it possible to determine the arity of a value's constructor?
Suppose I have a value x of type
data A = B Int | C
Hello Anatoly,
On Sat, Apr 11, 2009 at 20:44, Anatoly Yakovenko aeyakove...@gmail.comwrote:
i am trying to understand how data.data works. How would i traverse
the subterms of one type and build another type out of them.
something like this:
gmapQ (\a - Right a) (Just hello)
I am not
Hello,
I suppose Lennart is referring to type-level [1]. But type-level uses
functional dependencies, right?
There is also tfp [2], which uses type families. In general, how would you
say your work compares to these two?
Thanks,
Pedro
[1]
Hello Anatoly,
Bear in mind that gshow behaves a bit differently from the regular show
(namely regarding parenthesis and efficiency). You can also use standalone
deriving [1] to derive Show for those datatypes.
Cheers,
Pedro
[1]
Hello Henry,
Changes to GHC regarding the treatment of higher-rank types required a few
changes to that test too. You have to eta-expand the application of mkTT and
give it a type signature. Therefore, main becomes
print $ gzip (\x y - mkTT maxS x y) genCom1 genCom2
and you have to add the
Hello Conal,
What you've done looks very much like the Regular datatype [1] in the
rewriting library [2]. The rewriting library, as its name indicates, is very
much targeted at rewriting. For a more complete library using a sum of
products view (and without type synonyms), try the new release of
Hello Thomas,
I see this is a proposal for a partial implementation of #1673 (
http://hackage.haskell.org/trac/ghc/ticket/1673). Maybe it would be good if
the remaining syntax (associated datatypes and type families) would also be
defined and implemented in TH. Or maybe there isn't much demand
I think at least some sort of statistics of visits and downloads of a
package would be very useful, also for the developers to have an idea of how
many people are using the package.
Pedro
On Thu, Oct 23, 2008 at 13:12, Jason Dagit [EMAIL PROTECTED] wrote:
Hello,
I was thinking of fun little
Hi Jinjing,
I remember having written a report on Haskore some years ago, together with
a classmate. I think that the example of transformations in twelve-tone
technique (see [1]) is one that looks very nice in Haskore due to its
simplicity. It's also simple to present to people who do not know
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