[Haskell-cafe] Haskell type system and the lambda cube
Hi, I'm trying to get some better understanding of the theoretical foundations behind Haskell. I wonder, where exactly does Haskell type system fit within the lambda cube? http://en.wikipedia.org/wiki/Lambda_cube I guess it could also vary depending on what extensions are turned on. Thanks, Petr ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell type system and the lambda cube
Haskell has terms depending on types (polymorphic terms) and types depending on types (type families?), but no dependent types. 2009/5/24 Petr Pudlak d...@pudlak.name: Hi, I'm trying to get some better understanding of the theoretical foundations behind Haskell. I wonder, where exactly does Haskell type system fit within the lambda cube? http://en.wikipedia.org/wiki/Lambda_cube I guess it could also vary depending on what extensions are turned on. Thanks, Petr ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Eugene Kirpichov Web IR developer, market.yandex.ru ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell type system and the lambda cube
On Sun, May 24, 2009 at 12:18:40PM +0400, Eugene Kirpichov wrote: Haskell has terms depending on types (polymorphic terms) and types depending on types (type families?), but no dependent types. But how about undecidability? I'd say that lambda2 or lambda-omega have undecidable type checking, whereas Haskell's Hindley-Milner type system is decidable. From this I get that Haskell's type system can't be one of the vertices of the cube. (BWT, will some future version of Haskell consider including some kind of dependent types?) Petr 2009/5/24 Petr Pudlak d...@pudlak.name: Hi, I'm trying to get some better understanding of the theoretical foundations behind Haskell. I wonder, where exactly does Haskell type system fit within the lambda cube? http://en.wikipedia.org/wiki/Lambda_cube I guess it could also vary depending on what extensions are turned on. Thanks, Petr ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Eugene Kirpichov Web IR developer, market.yandex.ru ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell type system and the lambda cube
2009/5/24 Petr Pudlak d...@pudlak.name:
On Sun, May 24, 2009 at 12:18:40PM +0400, Eugene Kirpichov wrote:
Haskell has terms depending on types (polymorphic terms) and types
depending on types (type families?), but no dependent types.
But how about undecidability? I'd say that lambda2 or lambda-omega have
undecidable type checking, whereas Haskell's Hindley-Milner type system is
decidable.
It isn't, in the presence type classes (what else could the {-# LANG
UndecidableInstances #-} be for? :) ) and type families.
If all Haskell had would be HM, it would be System F.
From this I get that Haskell's type system can't be one of the
vertices of the cube.
Well, it surely has some features not described by the cube, but I'd
leave an explanation to the gurus around here :)
(BWT, will some future version of Haskell consider including some kind of
dependent types?)
Petr
2009/5/24 Petr Pudlak d...@pudlak.name:
Hi, I'm trying to get some better understanding of the theoretical
foundations
behind Haskell. I wonder, where exactly does Haskell type system fit
within the
lambda cube? http://en.wikipedia.org/wiki/Lambda_cube
I guess it could also vary depending on what extensions are turned on.
Thanks, Petr
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--
Eugene Kirpichov
Web IR developer, market.yandex.ru
--
Eugene Kirpichov
Web IR developer, market.yandex.ru
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Re: [Haskell-cafe] Haskell type system and the lambda cube
2009/5/24 Petr Pudlak d...@pudlak.name: If all Haskell had would be HM, it would be System F. That cannot be quite right, can it? System F has more powerful polymorphism than HM. Ciao, Janis. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Cabal, Time GHC 6.10.2
Duncan Coutts wrote: On Sun, 2009-05-17 at 09:17 +0100, Dominic Steinitz wrote: I get d...@linux-6ofq:~/asn1 runghc Setup.hs configure Configuring PER-0.0.20... Setup.hs: At least the following dependencies are missing: time -any -any but I have time d...@linux-6ofq:~/asn1 ghc-pkg list | grep time old-locale-1.0.0.1, old-time-1.0.0.2, packedstring-0.1.0.1, time-1.1.2.4 I think I can see why cabal isn't finding it: ghc-pkg dump --global | grep time-1.1.2.4 finds nothing and I believe that is what cabal uses to find things. The default for runghc Setup.hs configure is --global, but the default for cabal configure is --user. So if you're using the cabal program to install packages, then you can also us it to configure other packages. If for you need to use the runghc Setup.hs interface (e.g. in some system build scripts) and you want it to pick up packages from the user package db then use the --user flag. If you're constantly having to use the runghc Setup.hs interface and doing per-user installs is a pain then you can set the default for the cabal program to be global installs in the cabal config file (~/.cabal/config). I'll add this issue to the FAQ, it come up enough. If anyone else reading would like to eliminate this FAQ, then implementing this ticket is the answer: suggest use of --user if configure fails with missing deps that are in the user db http://hackage.haskell.org/trac/hackage/ticket/384 Duncan Duncan, Thanks very much. I'm happy to update the FAQ this weekend unless you have already done it. Dominic. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] FGL Question
Hello, I want to get the top or the bottom elements of a graph, but the following code appears to give the wrong answer in most cases, and the right answer in a few cases. Any ideas? -- get the most general or the least general elements graphMLGen :: Bool - Gr [Rule] () - Gr [Rule] () graphMLGen pm gr = buildGr unctxls where unctxls = map remadj ctxls remadj (_,n,r,_) = ([],n,r,[]) ctxls | pm = gsel (\x - outdeg' x == 0) gr | otherwise = gsel (\x - indeg' x == 0) gr Many thanks, Hans van Thiel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Data.Binary suboptimal instance
On Saturday 23 May 2009 23:23:05 Henning Thielemann wrote: Interesting solution however it does not perform very nice. I wrote microbenchmark ... skipped ... I didn'd do any profiling so I have no idea why writing is so slow. If you use top-level definition 'xs' the program might cache the list and second write is faster. You may change the order of tests in order check, whether that is the cause. There was separate process for each test. So caching could not affect results. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Cabal, Time GHC 6.10.2
On Sun, 2009-05-24 at 12:04 +0100, Dominic Steinitz wrote: I'll add this issue to the FAQ, it come up enough. If anyone else reading would like to eliminate this FAQ, then implementing this ticket is the answer: suggest use of --user if configure fails with missing deps that are in the user db http://hackage.haskell.org/trac/hackage/ticket/384 Thanks very much. I'm happy to update the FAQ this weekend unless you have already done it. Oh that'd be great. The Cabal website is managed as a darcs repo so just: darcs get http://haskell.org/cabal/ then edit the FAQ.markdown and run make to update the FAQ.html (uses pandoc). Then darcs send the patches to me or the cabal-devel mailing list. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] hackage version scheme survey
On Sat, 2009-05-23 at 19:57 -0500, br...@lorf.org wrote: On Saturday, 23.05.09 at 17:26, Don Stewart wrote: http://haskell.org/haskellwiki/Package_versioning_policy ? That helps a lot. I should have found that. But putting the policy on a web page doesn't seem to be working; there are a lot of non-compliant packages. I guess I'm surprised thah 'cabal check' doesn't complain about it and HDB doesn't reject them. We cannot force maintainers to follow the PVP, however we do have a plan to encourage adoption. The key is to get maintainers to opt-in. For packages that opt-in we will enforce it. Following the PVP is extra work for a maintainer so there need to be two sides to the bargain. The benefit to maintainers that we can enforce that all newly uploaded hackage packages that depend on their PVP-following package do actually specify an upper version bound. This benefits the maintainer because it lets them release new versions knowing that they are not breaking dependent packages. The bargain on the other side is that it's a benefit to you as a package author if you can rely on the proper versioning of the packages you depend on. In return however you must actually make proper use of that by specifying appropriate upper bounds (and the tools should be able to give helpful suggestions). However, like most of our grand plans, there's nobody actually working on implementing them at the moment. The key part of this plan is the PVP checker tool. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re: Re: [Haskell-cafe] Re: A problem with par and modules boundaries...
On Sat, 2009-05-23 at 20:42 -0400, Mario Blažević wrote:
On Sat 23/05/09 2:51 PM , Duncan Coutts duncan.cou...@worc.ox.ac.uk sent:
On Sat, 2009-05-23 at 13:31 -0400, Mario Blažević wrote:
...
So the function is not strict, and I don't understand
why GHC should evaluate the arguments before the call.
Right, it's lazy in the first and strict in the second argument. As far
as I can see we have no evidence that is is evaluating anything before
the call.
When I look at the Core definition of `test', it begins with
\ (n1axl::integer:GHCziIntegerziInternals.Integer)
(n2axn::integer:GHCziIntegerziInternals.Integer) -
%let as1sU :: integer:GHCziIntegerziInternals.Integer =
base:DataziList.prod1
(main:Main.factors2
(base:DataziList.prod1
(base:GHCziNum.upzulist main:Main.lvl main:Main.lvl n1axl)
base:DataziList.lvl1))
base:DataziList.lvl1
%in %case integer:GHCziIntegerziInternals.Integer
(ghczmprim:GHCziPrim.parzh
@
integer:GHCziIntegerziInternals.Integer
as1sU)
%of (dsapq::ghczmprim:GHCziPrim.Intzh)
I recommend using -ddump-simpl, as it produces more readable output.
To my untrained eyes, this looks like it's evaluating
product $ factors $ product [1..n1])
which is the first argument to `parallelize'.
That core code is doing:
let blah = product $ factors $ product thelist
in case par# blah of
_ - ...
So it's calling the primitive par# but nothing is forced to WHNF (except
the unused dummy return value of par#).
I assume that %case in Core evaluates the argument to WHNF, just like
case in Haskell.
Yes.
(In fact case in core always reduces to WHNF, where as in Haskell case
(...) of bar - (...) does not force anything.)
Then again, I could be completely misinterpreting what Core is, because
I can't find any call to `parallelize' before or after that. It appears
to be inlined in Core, regardless of whether the pragma
{-# INLINE parallelize #-}
is there or not.
Yes, because even without the pragma, ghc decides it's profitable to
inline.
Actually, I can't see any effect of that pragma in the
core files whatsoever, but it certainly has effect on run time.
How about diffing the whole core output (and using -ddump-simpl). If
there's a performance difference then there must be a difference in the
core code too.
Or do you mean to say that *your* installation of GHC behaves
the same when the function `parallelize' is defined in the same module and
when
it's imported?
Yes, exactly. With both ghc-6.10.1 and a very recent build of ghc-6.11
Duncan
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[Haskell-cafe] HPC Website FAQ
There's a nice website for HPC but it looks a bit out of date.
http://projects.unsafeperformio.com/hpc/
I wanted to send a patch to the FAQ for using HPC with .lhs files (you
have to run ghc -E to generate .hs files and strip some of the the lines
ghc generates: {-# LINE 1 ASNTYPE.lhs #-} #line 1 ASNTYPE.lhs).
Would it be possible for the author of HPC to make the website into a
darcs repo so that we send in patches? Apparently the Cabal website is
managed like that and it sounds like a good way of doing things in
general to me.
Thanks, Dominic.
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Re: Re: Re: Re: [Haskell-cafe] Re: A problem with par and modules boundaries...
I recommend using -ddump-simpl, as it produces more readable output.
Actually, I can't see any effect of that pragma in the
core files whatsoever, but it certainly has effect on
run time.
How about diffing the whole core output (and using -ddump-simpl). If
there's a performance difference then there must be a difference in the
core code too.
Ok.
$ ghc-6.11.20090421 --make primes-test.hs -threaded -O2 -ddump-simpl
main.simpl
$ time ./primes-test +RTS -N2
4001
real0m9.636s
user0m18.201s
sys 0m0.088s
$ ghc-6.11.20090421 --make primes-test.hs -threaded -O2 -ddump-simpl
imported.simpl
$ time ./primes-test +RTS -N24001
real0m17.547s
user0m17.453s
sys 0m0.052s
I can't exactly use diff because the generated identifier names are not the
same,
but after poring over with Emacs ediff I have found only one difference that's
not attributable to identifiers:
$diff main.simpl imported.simpl
...
223c232
a_s1rs [ALWAYS Just L] :: GHC.Integer.Internals.Integer
---
a_s1sV [ALWAYS Just S] :: GHC.Integer.Internals.Integer
...
Does this S vs. L difference have anything to do with strictness and laziness?
That line is a part of the `Main.test' definition:
$ diff -C 3 main.simpl imported.simpl
*** 217,244
[Arity 2
Str: DmdType LL]
Main.test =
! \ (n1_ahR :: GHC.Integer.Internals.Integer)
! (n2_ahT :: GHC.Integer.Internals.Integer) -
let {
! a_s1rs [ALWAYS Just L] :: GHC.Integer.Internals.Integer
LclId
[Str: DmdType]
! a_s1rs =
Data.List.prod1
(Main.factors2
(Data.List.prod1
! (GHC.Num.up_list Main.lvl Main.lvl n1_ahR) Data.List.lvl1))
Data.List.lvl1 } in
! case GHC.Prim.par# @ GHC.Integer.Internals.Integer a_s1rs
of _ { __DEFAULT -
case Data.List.prod1
(Main.factors2
(Data.List.prod1
! (GHC.Num.up_list Main.lvl Main.lvl n2_ahT) Data.List.lvl1))
Data.List.lvl1
! of x1_aUS { __DEFAULT -
! case GHC.Real.$wdivMod x1_aUS a_s1rs of _ { (# ww1_aUo, _ #) -
! ww1_aUo
}
}
}
Or do you mean to say that *your* installation of GHC
behaves the same when the function `parallelize' is defined in
the same module and when it's imported?
Yes, exactly. With both ghc-6.10.1 and a very recent build of ghc-6.11
As you can see, I'm using the 6.11.20090421 build. I looked at recent ones, but
the Linux builds seem to be less stable in May. I have the same results (though
I
didn't use -ddump-simpl) with 6.8.2. Can you recommend a different version to
try?
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Re: [Haskell-cafe] ANN: Haskell Hackathon in Philadelphia
Is there a list of projects that will be worked on during this, or how will that work? On Thu, May 21, 2009 at 5:39 PM, Brent Yorgey byor...@seas.upenn.eduwrote: Hi all! We are in the early stages of planning a Haskell hackathon/get together, Hac φ, to be held this summer at the University of Pennsylvania, in Philadelphia. Right now we're looking at two possible dates: June 19-21or July 24-26 If you might be interested in attending, please add your name on the wiki page: http://www.haskell.org/haskellwiki/Hac_%CF%86 You can also note whether either of those dates absolutely doesn't work for you. (If you don't have an account on the wiki, you can email Ashley Yakeley for an account [1], or feel free to just respond to this email.) Expect more details (such as a nailed-down date) soon, once we have gauged the level of interest. Hope to see you in Philadelphia! Brent (byorgey) Daniel Wagner (dmwit) [1] http://haskell.org/haskellwiki/HaskellWiki:New_accounts ___ 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
Re: Re: Re: Re: [Haskell-cafe] Re: A problem with par and modules boundaries...
On Sun, 2009-05-24 at 12:48 -0400, Mario Blažević wrote: How about diffing the whole core output (and using -ddump-simpl). If there's a performance difference then there must be a difference in the core code too. I can't exactly use diff because the generated identifier names are not the same, but after poring over with Emacs ediff I have found only one difference that's not attributable to identifiers: $diff main.simpl imported.simpl ... 223c232 a_s1rs [ALWAYS Just L] :: GHC.Integer.Internals.Integer --- a_s1sV [ALWAYS Just S] :: GHC.Integer.Internals.Integer ... Good find! Does this S vs. L difference have anything to do with strictness and laziness? Yes. So, I think we should open a ghc but report with all the details, particularly the example's source, the ghc version and that highlight of that strictness difference. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] `seq` and categories
On the IRC channel a few days ago, it was said that, as long as we allow `seq`, Hask is not a valid category. Doesn't this basically mean that a very large amount of Haskell -- anything with strictness annotations -- can not be described in a category Hask? -- Jason Dusek ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] FGL Question
Hans van Thiel wrote: Hello, I want to get the top or the bottom elements of a graph, but the following code appears to give the wrong answer in most cases, and the right answer in a few cases. Any ideas? -- get the most general or the least general elements graphMLGen :: Bool - Gr [Rule] () - Gr [Rule] () graphMLGen pm gr = buildGr unctxls where unctxls = map remadj ctxls remadj (_,n,r,_) = ([],n,r,[]) ctxls | pm = gsel (\x - outdeg' x == 0) gr | otherwise = gsel (\x - indeg' x == 0) gr Hi Hans, I believe the problem is to do with the inductive nature of the FGL library. A graph in FGL is a series of contexts, each corresponding to a node. Each context contains lists of links to/from the latest node to nodes in previous contexts. Each link is only recorded once, and whether it appears in the context for the source or destination node depends on the order that the graph is constructed. For example, here's a simple graph: graph :: Gr Int String graph = mkGraph (zip [0..4] [0..4]) [(0,1,a), (0,2,b), (1,2,c), (2,1,d), (3,0,e)] main :: IO () main = putStrLn $ show $ gsel (const True) graph The output is (here, the last/outermost context is listed first): [([(c,1),(b,0)],2,2,[(d,1)]),([(a,0)],1,1,[]),([],3,3,[(e,0)]),([],0,0,[]),([],4,4,[])] Even though 0 has two outgoing links, its context shows no links in either direction -- hence why your code wasn't always working. Generally, don't use the Context functions much, and use the functions involving Node instead. Here's some simple solutions: If all you need afterwards is the node labels, I'd suggest something like: labelsZeroOut gr = [l | (n, l) - labNodes gr, outdeg gr n == 0] If you do need to retain the graph structure, I'd suggest: graphZeroOut gr = delNodes (filter ((== 0) . outdeg gr) $ nodes gr) gr Hope that helps, Neil. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] `seq` and categories
jason.dusek: On the IRC channel a few days ago, it was said that, as long as we allow `seq`, Hask is not a valid category. Doesn't this basically mean that a very large amount of Haskell -- anything with strictness annotations -- can not be described in a category Hask? I'm not sure of the category theoretic story, but I'd imagine so. For background on how seq confuses reasoning (and how to restore it), see Janis Voigtlaender's extensive, thorough work on the topic. http://wwwtcs.inf.tu-dresden.de/~voigt/ Also, mail: seq does not preclude parametricity http://www.mail-archive.com/haskell-cafe@haskell.org/msg19820.html -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Defining a CPP macro when building documentation
Hello all,
I have been exposed to a problem that have happened to others too, and
since I have found a (scary) solution with the help of Duncan Coutts,
I'm now sharing it with you.
The reason I wanted to pass specific CPP flags to haddock was to allow
the documentation of the full module to get built, even when only parts
of the module would end up getting compiled because of restrictions on
the build platform.
In this mail, Duncan Coutts gives a very helpful bit of code to override
the haddockHook and pass additional options to haddock :
http://www.haskell.org/pipermail/haskell-cafe/2008-December/051785.html
In my case, I needed something very similar, except that I needed to
pass those additional options to hsc2hs which my code uses. This worked
fine as long as the cabal commands sequence was [configure,haddock]
and not [configure,build,haddock]. The reason for this is that in
the latter case, the library wasn't being processed again, but output of
previous runs of hsc2hs were reused.
So I worked around this with an ugly hack that removes the .hs files
before running haddock, in order to force re-processing! Here's the
final code I ended up with :
import Distribution.Simple
import Distribution.Simple.LocalBuildInfo (LocalBuildInfo(withPrograms),
buildDir)
import Distribution.Simple.Program (userSpecifyArgs)
import System.Directory
import System.FilePath
-- Define __HADDOCK__ when building documentation.
main = defaultMainWithHooks simpleUserHooks {
haddockHook = \pkg lbi h f - do
let progs = userSpecifyArgs hsc2hs [-D__HADDOCK__] (withPrograms lbi)
removePreProcessedFiles (buildDir lbi)
haddockHook simpleUserHooks pkg lbi { withPrograms = progs } h f
}
-- Horrible hack to force re-processing of the .hsc file. Otherwise
-- the __HADDOCK__ macro doesn't end up being defined.
removePreProcessedFiles :: FilePath - IO ()
removePreProcessedFiles dir =
removeFile (dir / System/BSD/Sysctl.hs)
`catch` \_ - return ()
Cheers,
Maxime
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[Haskell-cafe] ANN: bsd-sysctl 1.0.3
I'm pleased to announce the release of bsd-sysctl 1.0.3, a package that provides a System.BSD.Sysctl module allowing access to the C sysctl(3) API. It should fully work on FreeBSD, NetBSD and Mac OS X platforms; it should also work on OpenBSD and Linux, although looking up sysctl's by name isn't supported there, and I believe the sysctl API doesn't return anything useful under Linux. The package is available here: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/bsd-sysctl-1.0.3 As this is my first package on hackage, I'm eager to hear about any comments on this code. Cheers, Maxime ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] the problem of design by negation
Design-by-negativity can *be* a way of being creative. I've lost count of the number of times that I've been explaining to someone why something can't be done, and suddenly realised that one of the reasons was invalid and seen how to do it. The key is not whether you explore the design space from a positive end or from a negative end, but whether you *explore* it. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Data.Binary suboptimal instance
andrewcoppin: The problem seems to boil down to this: The Binary instance for Double (and Float, by the way) is... well I guess you could argue it's very portable, but efficient it isn't. As we all know, an IEEE-754 double-precision floating-point number occupies 64 bits; 1 sign bit, 11 exponent bits, and 52 mantissa bits (implicitly 53). I had assumed that the Binary instance for Double would simply write these bits to disk, requiring approximately 0 computational power, and exactly 64 bits of disk space. I was wrong. Is there any danger that there might be some kind of improvement to the Double instance in the next version of Data.Binary? This was discussed last week. A patch was posted implementing more efficient low level double encodings. Google for the thread: Data.Binary and little endian encoding. Tim ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] the problem of design by negation
Richard O'Keefe wrote: Design-by-negativity can *be* a way of being creative. I've lost count of the number of times that I've been explaining to someone why something can't be done, and suddenly realised that one of the reasons was invalid and seen how to do it. The key is not whether you explore the design space from a positive end or from a negative end, but whether you *explore* it. Hi Richard, I think we using positive and negative in a bit of a different sense (which may be my fault for not explaining perfectly in the first post). There are both positive and negative *facts* about design. There are things you can do, and things you can't. These are facts. I'm referring more to a specific kind of process (a specific kind of exploration)---in my terms, design by negation means that you dominant activity in design in cutting away possibilities, and what's left (however awkward) is what you must build. I have done this by habit, but I would like to shift into a mode of design that is focused on construction rather than destruction---to view design as an opportunity to meet most goals by clever combining of facets. Thanks, Mike ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] the problem of design by negation
The main objection I have to the negative process (can't be done) is that is so often bogus. Proof by lack of imagination. I guess it works for Richard, though not for Michael's architect, because Richard is able to catch his bogus reasoning *and he is willing*** to do so, which requires humility and ego-strength. - Conal On Sun, May 24, 2009 at 6:35 PM, Michael P Mossey m...@alumni.caltech.eduwrote: Richard O'Keefe wrote: Design-by-negativity can *be* a way of being creative. I've lost count of the number of times that I've been explaining to someone why something can't be done, and suddenly realised that one of the reasons was invalid and seen how to do it. The key is not whether you explore the design space from a positive end or from a negative end, but whether you *explore* it. Hi Richard, I think we using positive and negative in a bit of a different sense (which may be my fault for not explaining perfectly in the first post). There are both positive and negative *facts* about design. There are things you can do, and things you can't. These are facts. I'm referring more to a specific kind of process (a specific kind of exploration)---in my terms, design by negation means that you dominant activity in design in cutting away possibilities, and what's left (however awkward) is what you must build. I have done this by habit, but I would like to shift into a mode of design that is focused on construction rather than destruction---to view design as an opportunity to meet most goals by clever combining of facets. Thanks, Mike ___ 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
