[Haskell-cafe] How to fix this problem in FreeBSD ?
/usr/ports/devel/hs-ghc-pathssudo make install clean === hs-ghc-paths-0.1.0.5_1 depends on executable: ghc - found === Configuring for hs-ghc-paths-0.1.0.5_1 [1 of 1] Compiling Main ( Setup.hs, Setup.o ) Setup.hs:18:22: Not in scope: `preMakefile' *** Error code 1 Stop in /usr/ports/devel/hs-ghc-paths. Sincerely! - e^(π⋅i) + 1 = 0 -- View this message in context: http://old.nabble.com/How-to-fix-this-problem-in-FreeBSD---tp28714271p28714271.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to fix this problem in FreeBSD ?
Which version of GHC, which version of Cabal, and what is the Makefile? zaxis z_a...@163.com writes: /usr/ports/devel/hs-ghc-pathssudo make install clean === hs-ghc-paths-0.1.0.5_1 depends on executable: ghc - found === Configuring for hs-ghc-paths-0.1.0.5_1 [1 of 1] Compiling Main ( Setup.hs, Setup.o ) Setup.hs:18:22: Not in scope: `preMakefile' *** Error code 1 Stop in /usr/ports/devel/hs-ghc-paths. Sincerely! - e^(π⋅i) + 1 = 0 -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to fix this problem in FreeBSD ?
ghc --version
The Glorious Glasgow Haskell Compilation System, version 6.10.4
cabal --version
cabal-install version 0.8.2
using version 1.8.0.2 of the Cabal library
cat Makefile
# New ports collection makefile for: hs-ghc-paths
# Date created:July 09 2009
# Whom:Giuseppe Pilichi aka Jacula Modyun jac...@gmail.com
#
# $FreeBSD: ports/devel/hs-ghc-paths/Makefile,v 1.3 2010/05/26 11:18:37
jacula Exp $
PORTNAME= ghc-paths
PORTVERSION=0.1.0.5
PORTREVISION= 1
CATEGORIES= devel haskell
MAINTAINER= hask...@freebsd.org
COMMENT=Utility looking for GHC installation directories
CABAL_SETUP=Setup.hs
.if defined(SLAVE)
GHC_CMD=ghc
.endif
.include ${.CURDIR}/../../lang/ghc/bsd.cabal.mk
.include bsd.port.mk
Ivan Miljenovic wrote:
Which version of GHC, which version of Cabal, and what is the Makefile?
zaxis z_a...@163.com writes:
/usr/ports/devel/hs-ghc-pathssudo make install clean
=== hs-ghc-paths-0.1.0.5_1 depends on executable: ghc - found
=== Configuring for hs-ghc-paths-0.1.0.5_1
[1 of 1] Compiling Main ( Setup.hs, Setup.o )
Setup.hs:18:22: Not in scope: `preMakefile'
*** Error code 1
Stop in /usr/ports/devel/hs-ghc-paths.
Sincerely!
-
e^(π⋅i) + 1 = 0
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-
e^(π⋅i) + 1 = 0
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Re: [Haskell-cafe] Wire GUI
Malcolm Wallace wrote: I'm looking at a project which involves a GUI where you can insert components and wire up connections between them. Obviously the details of what the components are and what code gets executed for them is domain-specific, however the general idea of graphically wiring things together is quite generic. Has anybody already put together a Haskell library for doing this kind of thing? Blobs. (warning: some danger of bitrot) http://www.cs.york.ac.uk/fp/darcs/Blobs/ Thanks for the tip. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Wire GUI
Conal Elliot's talk on Tangible Functional Programming might be of interest. http://www.youtube.com/watch?v=faJ8N0giqzw On 29 May 2010 09:43, Andrew Coppin andrewcop...@btinternet.com wrote: Malcolm Wallace wrote: I'm looking at a project which involves a GUI where you can insert components and wire up connections between them. Obviously the details of what the components are and what code gets executed for them is domain-specific, however the general idea of graphically wiring things together is quite generic. Has anybody already put together a Haskell library for doing this kind of thing? Blobs. (warning: some danger of bitrot) http://www.cs.york.ac.uk/fp/darcs/Blobs/ Thanks for the tip. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Math questions
Mujtaba Boori wrote: sure I did enjoy the discussion here Yitzchak Gale. I have already submitted several questions ,and you guys were very helpful. However , I am not sure how I will use Haskell other than my Haskell course that has just finished. I would very much recommend the Real World Haskell book if you want to write real programs with it. I was interested in Haskell for a long time, but it was only after I read that book that I could see how to structure larger programs. I've only written a few real world programs with Haskell, but I do think there are some situations where it reduces development time compared to other languages. Ideally, I suppose, you would have a type-safe language with the flexibility of Python. Haskell isn't quite that, but it probably gets closer than other languages, thanks to its flexible type system and support for type inference. It's also particularly good for parsing text (Parsec is much nicer than yacc) and multithreading (the STM module is particularly good). Downsides: the libraries aren't as complete or well tested as some other languages. Also I suppose it has to be said that functions which update state can become clumsy. The state monad helps with this, but you can still find yourself writing more code than you would need in other languages. Pete PS here is a more serious answer to the original question... test f1 f2 = and [f1 i == f2 i | i - [1..100]] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: [Haskell] Re: Work on Video Games in Haskell
Edward Kmett ekm...@gmail.com writes: On Wed, May 26, 2010 at 5:22 PM, Pierre-Etienne Meunier span dir=ltrmailto:pierreetienne.meun...@gmail.com/span wrote: Well in this case I#39;d be really interested in seeing how the can tell the difference, be it only from a simple complexity theoretic point of view ! I understand they may look for common patterns in their compiler code to tell the difference between GHC#39;s generated code and theirs, but pretending they can do it in this case only shows that Apple lawyers never communicate with the engineers. I think it is more a matter of Jobs trying to find any way he could to quickly block Adobe#39;s attempted end-run around his blockade against Flash apps.While we can all acknowledge the technical impossibility of identifying the original source language of a piece of code, all they need is to raise the spectre of doubt, and they have practically gutted all concern of a cross platform development environment emerging, because no sound business plan can be built on I hope my major and only possible distributor doesn#39;t figure out what I#39;m doing! While it may be difficult to identify the original source language of an arbitrary piece of code, it is much simpler to identify Haskell as the original source language of a GHC-compiled piece of code for most pieces of code. There are a number of interesting discussions on this issue at the sites below: [1] Daring Fireball: New iPhone Developer Agreement Bans the Use of Adobe's Flash-to-iPhone Compiler http://daringfireball.net/2010/04/iphone_agreement_bans_flash_compiler [2] Hacker News | Getting away from the frenzied rhetoric, my opinion is that what Apple really wa... http://news.ycombinator.com/item?id=1250946 [3] Knowing .NET » Blog Archive » The Absurdity of Apple’s New iPhone Restrictions http://www.knowing.net/index.php/2010/04/09/using-mathematica-to-generate-the-elements-appebook/ [4] Why does everything suck?: Steve Jobs Has Just Gone Mad http://whydoeseverythingsuck.com/2010/04/steve-jobs-has-just-gone-mad.html [5] Apple takes aim at Adobe... or Android? http://arstechnica.com/apple/news/2010/04/apple-takes-aim-at-adobe-or-android.ars In addition, the following article sheds some light on the historical background for the initial Apple vs. Adobe schism: [6] Rhapsody and blues http://arstechnica.com/staff/fatbits/2008/04/rhapsody-and-blues.ars Curiously, in the original Apple Macintosh Superbowl commercial (see http://video.google.com/videoplay?docid=-715862862672743260#), Apple (then Apple Computer) proclaimed the following: On January 24th, Apple Computer will introduce Macintosh. And you'll see why 1984 won't be like 1984. George Orwell's novel, _1984_, was essentially about freedom of expression (among a number of other freedoms). Ironically, by prohibiting freedom of expression in the choice of a programming language for the iPhone and requiring that all applications be originally written in Objective-C, C, C++, or JavaScript as executed by the iPhone OS Webkit engine, Apple has now become the epitome of the very thing it had originally set out *not* to be. -- Benjamin L. Russell [1] Gruber, John. New iPhone Developer Agreement Bans the Use of Adobe’s Flash-to-iPhone Compiler. n.p. 8 Apr. 2010. Web. 29 May 2010. http://daringfireball.net/2010/04/iphone_agreement_bans_flash_compiler. [2] raganwald. n.t. _Hacker News._ Y Combinator. 9 Apr. 2010. Web. 29 May 2010. http://news.ycombinator.com/item?id=1250946. [3] O'Brien, Larry. The Absurdity of Apple’s New iPhone Restrictions. _Knowing .NET._ n.p. 9 Apr. 2010. Web. 29 May 2010. http://www.knowing.net/index.php/2010/04/09/using-mathematica-to-generate-the-elements-appebook/ . [4] Williams, Hank. Steve Jobs Has Just Gone Mad. _Why does everything suck?: Exploring the tech marketplace from 10,000 feet._ n.p. 8 Apr. 2010. Web. 29 May 2010. http://whydoeseverythingsuck.com/2010/04/steve-jobs-has-just-gone-mad.html. [5] Bright, Peter. Apple takes aim at Adobe... or Android? _Ars Technica._ Condé Nast Digital. Apr. 2010. Web. 29 May 2010. http://arstechnica.com/apple/news/2010/04/apple-takes-aim-at-adobe-or-android.ars. [6] Siracusa, John. Rhapsody and blues. _Ars Technica._ Condé Nast Digital. 3 Apr. 2008. Web. 29 May 2010. http://arstechnica.com/staff/fatbits/2008/04/rhapsody-and-blues.ars. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Reproducible Bug in Emacs' haskell-mode
Hi all,
I have a reproducible bug in Emacs' Haskell mode where Emacs gets
stuck in an endless loop. I am using GNU Emacs 23.0.93.1. To
reproduce:
1. Use a bad Language pragma eg.
{-# LANGUAGE FlexibleTypes #-}
2. Load a GHCI instance with C-c C-l. GHCI outputs the following error:
unsupported extension: FlexibleTypes
3. Fix the pragma:
{-# FlexibleInstances -#}
4. Try to load the file again with C-c C-l and Emacs gets stuck.
-deech
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[Haskell-cafe] Re: [web-devel] Google Summer of Code: BlazeHTML RFC
Q3: Which HTML version would you preferably use? HTML 5. google summer of code should be about pushing the new and exciting. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: [web-devel] Google Summer of Code: BlazeHTML RFC
Matt Parker moonmaster9...@gmail.com writes: Q3: Which HTML version would you preferably use? HTML 5. google summer of code should be about pushing the new and exciting. Yes, definitely, this should be the default IMO. G -- Gregory Collins g...@gregorycollins.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Reproducible Bug in Emacs' haskell-mode
Try the following:
1) M-x toggle-debug-on-quit (so that it's enabled)
2) Follow your instructions below
3) When it's stuck, do C-g to stop it trying to load the file.
Just so you know, there's also a dedicated mailing list for the Haskell
mode in Emacs; see here for more information:
http://projects.haskell.org/haskellmode-emacs/
aditya siram aditya.si...@gmail.com writes:
Hi all,
I have a reproducible bug in Emacs' Haskell mode where Emacs gets
stuck in an endless loop. I am using GNU Emacs 23.0.93.1. To
reproduce:
1. Use a bad Language pragma eg.
{-# LANGUAGE FlexibleTypes #-}
2. Load a GHCI instance with C-c C-l. GHCI outputs the following error:
unsupported extension: FlexibleTypes
3. Fix the pragma:
{-# FlexibleInstances -#}
4. Try to load the file again with C-c C-l and Emacs gets stuck.
-deech
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ivan.miljeno...@gmail.com
IvanMiljenovic.wordpress.com
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Re: [Haskell-cafe] Why Either = Left | Right instead of something like Result = Success | Failure
Vo Minh Thu wrote: Control.Monad.Error provides an instance for Either. Donn Cave wrote: ... in the mtl transformer library, in case anyone else besides myself didn't know that. And I see it has to be there because it depends on the Error typeclass. Daniel Fischer daniel.is.fisc...@web.de writes: Which is considered a wart by some. (Either left) has a perfectly valid Monad instance for any type left Indeed, and it is one of the most useful Monads there is. The Either monad provides short-circuiting logic, so that you can exit an arbitrary number of levels of nested calculation. The type Either a b returns a if the calculation exits, or b if it completes without exiting. Exiting on an error condition is one tiny corner case of multi-level exit, so it is a shame that the mtl library defines an orphan instance. By doing that, it hijacks the Either monad and monopolizes it for its own specialized purpose. This is the classic example why defining orphan instances is so dangerous. Now, instead of the natural use of Either for short-circuiting logic, we are forced to find other solutions, such as: o use the MonadPlus instance of Maybe and write everything additively, using mplus and return instead of (=) and Left. That is equivalent to the Either monad, but in practice it ends up looking a lot messier and harder to read. o use a CPS-based monad, like Cont or LogicT. I find those highly obfuscated, and a huge amount of complexity overkill for most tasks. o use a clone of Either, like the Exit monad. That is currently the best workaround, in my opinion. http://www.haskell.org/haskellwiki/New_monads/MonadExit Regards, Yitz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Proposal to solve Haskell's MPTC dilemma
On Fri, May 28, 2010 at 2:36 AM, Isaac Dupree
m...@isaac.cedarswampstudios.org wrote:
On 05/27/10 17:42, Carlos Camarao wrote:
On Thu, May 27, 2010 at 5:43 PM, David Menendezd...@zednenem.com
wrote:
On Thu, May 27, 2010 at 10:39 AM, Carlos Camarao
carlos.cama...@gmail.com wrote:
Isaac Dupree:
Your proposal appears to allow /incoherent/ instance selection.
This means that an expression can be well-typed in one module, and
well-typed in another module, but have different semantics in the
two modules. For example (drawing from above discussion) :
module C where
class F a b where f :: a - b
class O a where o :: a
module P where
import C
instance F Bool Bool where f = not
instance O Bool where o = True
k :: Bool
k = f o
module Q where
import C
instance F Int Bool where f = even
instance O Int where o = 0
k :: Bool
k = f o
module Main where
import P
import Q
-- (here, all four instances are in scope)
main = do { print P.k ; print Q.k }
-- should result, according to your proposal, in
-- False
-- True
-- , am I correct?
If qualified importation of k from both P and from Q was specified, we
would have two *distinct* terms, P.k and Q.k.
I think Isaac's point is that P.k and Q.k have the same definition (f
o). If they don't produce the same value, then referential
transparency is lost.
--
Dave Menendezd...@zednenem.com
http://www.eyrie.org/~zednenem/ http://www.eyrie.org/%7Ezednenem/
http://www.eyrie.org/%7Ezednenem/
The definitions of P.k and Q.k are textually the same but the contexts are
different. f and o denote distinct values in P and Q. Thus, P.k and
Q.k
don't have the same definition.
Oh, I guess you are correct: it is like defaulting: it is a similar effect
where the same expression means different things in two different modules as
if you had default (Int) in one, and default (Bool) in the other. Except:
Defaulting according to the standard only works in combination with the 8
(or however many it is) standard classes; and defaulting in Haskell is
already a bit poorly designed / frowned upon / annoying that it's specified
per-module when nothing else in the language is*.(that's a rather
surmountable argument)
It may be worth reading the GHC user's guide which attempts to explain the
difference between incoherent and non-incoherent instance selection,
http://www.haskell.org/ghc/docs/6.12.2/html/users_guide/type-class-extensions.html#instance-overlap
I didn't read both it and your paper closely enough that I'm sure anymore
whether GHC devs would think your extension would require or imply
-XIncoherentInstances ... my intuition was that IncoherentInstances would be
implied...
*(it's nice when you can substitute any use of a variable, such as P.k,
with the expression that it is defined as -- i.e. the expression written so
that it refer to the same identifiers, not a purely textual substitution --
but in main above, you can't write [assuming you imported C] print (f o)
because it will be rejected for ambiguity. (Now, there is already an
instance-related situation like this where Main imports two different
modules that define instances that overlap in an incompatible way, such as
two different instances for Functor (Either e) -- not everyone is happy
about how GHC handles this, but at least those overlaps are totally useless
and could perhaps legitimately result in a compile error if they're even
imported into the same module.))
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I have no idea why you think IncoherentInstances would be implied. The
proposal says: do not issue ambiguity error if, using whatever means
permitted and specified (OverlappingInstances, IncoherentInstances,
whatever), you can select a single instance.
The situation is as if we a FD:
module C where
class F a b | a-b where f :: a - b
class O a where o :: a
module P where
import C; instance F Bool Bool where f = not
instance O Bool where o = True
g:: Bool - Bool
g = f
k::Bool
k = g o
module Q where
import C
instance F Int Bool where f = even
instance O Int where o = 0
g::Int-Bool
g = f
k :: Bool
k = g o
module Main where
import P
import Q
main = do { print P.k ; print Q.k }
Cheers,
Carlos
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Re: [Haskell-cafe] Re: Proposal to solve Haskell's MPTC dilemma
On 05/29/10 21:24, Carlos Camarao wrote:
The situation is as if we a FD:
Well, that is indeed equivalent here in the second argument of class F,
but I constructed the example to show an issue in the class's *first*
argument.
Notice you needed to add type-signatures, on the functions you named g
-- in particular their first arguments -- to make the example work with
only FDs?
module C where
class F a b | a-b where f :: a - b
class O a where o :: a
module P where
import C; instance F Bool Bool where f = not
instance O Bool where o = True
g:: Bool - Bool
g = f
k::Bool
k = g o
module Q where
import C
instance F Int Bool where f = even
instance O Int where o = 0
g::Int-Bool
g = f
k :: Bool
k = g o
you can inline these k-definitions into module Main and it will work
(modulo importing C).
module Main where
import C
import P
import Q
main = do { print (((f :: Bool - Bool) o) :: Bool);
print (((f :: Int - Bool) o) :: Bool) }
These are two different expressions that are being printed, because
:: Bool - Bool is different from :: Int - Bool. In my example
of using your proposal, one cannot inline in the same way, if I
understand correctly (the inlining would cause ambiguity errors --
unless of course the above distinct type-signatures are added).
If your proposal was able to require those -- and only those -- bits of
type signatures that were essential to resolve the above ambiguity; for
example, the ( :: Int) below,
module Q where
import C
instance F Int Bool where f = even
instance O Int where o = 0
k = f (o :: Int)
, then I would be fine with your proposal (but then I suspect it would
have to be equivalent to FDs -- or in other words, that it's not really
practical to change your proposal to have that effect).
I stand by my assertion that the same expression means different things
in two different modules is undesirable, (and that I suspect but am
unsure that this undesirability is named incoherent instances).
I'm trying to work out whether it's possible to violate the invariants
of a Map by using your extension (having it select a different instance
in two different places, given the same type).. I think, no it is not
possible for Ord or any single-parameter typeclass, though there might
be some kind of issues with multi-parameter typeclasses, if the library
relies on a FD-style relationship between two class type-parameters and
then two someones each add an instance that together violate that
implied FD-relationship (which is allowed under your scheme, unlike if
there was an actual FD). Er, odd, I need to play with some actual FD
code to think about this, but I'm too sleepy / busy packing for a trip.
Did any of the above make sense to you? It's fine if some didn't, type
systems are complicated... and please point out if something I said was
outright wrong.
-Isaac
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[Haskell-cafe] A question on existential types and Church encoding
Hello, A professor of mine was recently playing around during a lecture with Church booleans (I.e., true = \x y - x; false = \x y - y) in Scala and OCaml. I missed what he did, so I reworked it in Haskell and got this: type CB a = a - a - a ct :: CB aC ct x y = x cf :: CB a cf x y = y cand :: CB (CB a) - CB a - CB a cand p q = p q cf cor :: CB (CB a) - CB a - CB a cor p q = p ct q I found the lack of type symmetry (the fact that the predicate arguments don't have the same time) somewhat disturbing, so I tried to find a way to fix it. I remembered reading about existential types being used for similar type-hackery, so I added quantification to the CB type and got type CB a = forall a . a - a - a ctrue :: CB a ctrue x y = x cfalse :: CB a cfalse x y = y cand :: CB a - CB a - CB a cand p q = p q cfalse cor :: CB a - CB a - CB a cor p q = p ctrue q which works. But I haven't the faintest idea why that forall in the type makes things work... I just don't fully understand existential type quantification. Could anyone explain to me what's going on that makes the second code work? Thanks, Cory ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
