[Haskell-cafe] Re: What I learned from my first serious attempt low-level Haskell programming
Stefan O'Rear wrote: 2. Parameters are very expensive. Our type of functions that build (ignoring CPS for the time being) was MBA# - Int# - [ByteString], where the Int# is the current write pointer. Adding an extra Int# to cache the size of the array (rather than calling sMBA# each time) slowed the code down ~2x. Conversely, moving the write pointer into the byte array (storing it in bytes 0#, 1#, 2#, and 3#) sped the code by 4x. If you were measuring on x86 then parameters are passed on the stack, which may be expensive. On x86_64 the first 3 arguments are passed in registers, which is usually a win, but if the function immediately does an eval they need to be saved on the stack anyway. Still, 4x sounds like a lot, perhaps you managed to avoid a stack check in the inner loop or something. 3. MBA# is just as fast as Addr#, and garbage collected to boot. Not really surprising, that. 4. You can't keep track of which version of the code is which, what is a regression, and what is an enhancement. Don't even try. Next time I try something like this I will make as much use of darcs as possible. Absolutely - if you'd used darcs, then we could peer in more detail at changes that you thought gave counter-intuitive results. Simon Peyton-Jones wrote: | 5. State# threads clog the optimizer quite effectively. Replacing |st(n-1)# with realWorld# everywhere I could count on data |dependencies to do the same job doubled performance. The idea is that the optimiser should allow you to write at a high level, and do the book keeping for you. When it doesn't, I like to know, and preferably fix. If you had a moment to boil out a small, reproducible example of this kind of optimisation failure (with as few dependencies as poss), then I'll look to see if the optimiser can be cleverer. Yes, and *please* add some of this folklore to the performance wiki at http://haskell.org/haskellwiki/Performance, if you have the time. Cheers, Simon ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] RE: What I learned from my first serious attempt low-level Haskell programming
| 5. State# threads clog the optimizer quite effectively. Replacing
|st(n-1)# with realWorld# everywhere I could count on data
|dependencies to do the same job doubled performance.
The idea is that the optimiser should allow you to write at a high level, and
do the book keeping for you. When it doesn't, I like to know, and preferably
fix.
If you had a moment to boil out a small, reproducible example of this kind of
optimisation failure (with as few dependencies as poss), then I'll look to see
if the optimiser can be cleverer.
|
| 6. The inliner is a bit too greedy. Removing the slow-path code from
|singleton doesn't help because popSingleton is only used once; but
|if I explicitly {-# NOINLINE popSingleton #-}, the code for
|singleton itself becomes much smaller, and inlinable (15% perf
|gain). Plus the new singleton doesn't allocate memory, so I can
|use even MORE realWorld#s.
That's a hard one! Inlining functions that are called just once is a huge win
usually. I don't know how to spot what you did in an automated way.
thanks
Simon
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Re: [Haskell-cafe] 25k lines of ASP to 4.2k lines of Haskell, with considerably more functionality
Hello Adam, Thursday, April 5, 2007, 7:04:32 AM, you wrote: Haskell in the real world: http://braintreehemp.com.au/ in the shopping section, there are choice between men, women and special creatures. doesn't slave-trade prohibited by civil laws? -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Automatic derivation (TemplateHaskell?)
Stefan, Data.Derive is a most awesome piece of code! Is there soemething in DrIFT that you did not like that made you write it? Thanks a lot! On Apr 5, 2007, at 12:48 AM, Stefan O'Rear wrote: Data.Derive can do this. In an attempt to avoid munging the relevent files they are attached. -- http://wagerlabs.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Trouble trying to find packages for ubuntu linux
In the spirit of... I hate package chasing, cabal doesn't do this automatically (yet), and hard disk space is cheap... Here is a script to just hit the deb/ubuntu repos and install as much haskell-loooking stuff as possible. If you're going to do this, I would recommend pulling at least from the feisty repo, as described in pupeno's blog, and in more detail in my other post linked above. Basically, this installs all ghc6* packages, with ad-hoc blocking of packages that cause aptitude to complain. The basic approach seems sound though. If it gets stuck at some point, I'll just add the offending package to the filter list. (I suspect there's a more intelligent way to do this if you know debian package management better than I do.) The script below has been cranking away for a pretty long time now -- so not only may your mileage vary, mine isnt' even yet. I also wouldn't recommend doing this on a production server. (When/if I hose my system, I can reload a virgin ubuntu in under five minutes using my linode control panel.) * apt-cache search libghc6 | ghc -e 'interact $ unlines . map (\l - head $ words l ) . lines' \ | grep -ivE \(ghc6-hopengl\|libghc6-c2hs-dev\) \ | xargs apt-get -y install 2007/3/16, Chad Scherrer [EMAIL PROTECTED]: Brian, I had this exact problem, and I found this approach to work wonderfully: http://pupeno.com/2006/12/17/unstable-packages-on-ubuntu/ Chad ___ 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: [Haskell-cafe] Re: Trouble trying to find packages for ubuntu linux
This approach is fleshed out at http://groups.google.de/group/fa.haskell/browse_thread/thread/ceabae2c3fdc8abc/814a86d89c3f7d28?lnk=stq=tphyahoo+haskell+ubunturnum=1hl=en#814a86d89c3f7d28 2007/3/16, Chad Scherrer [EMAIL PROTECTED]: Brian, I had this exact problem, and I found this approach to work wonderfully: http://pupeno.com/2006/12/17/unstable-packages-on-ubuntu/ Chad ___ 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: [Haskell-cafe] Re: Trouble trying to find packages for ubuntu linux
and in more detail in my other post linked above. I meant, linked below. 2007/4/5, Thomas Hartman [EMAIL PROTECTED]: In the spirit of... I hate package chasing, cabal doesn't do this automatically (yet), and hard disk space is cheap... Here is a script to just hit the deb/ubuntu repos and install as much haskell-loooking stuff as possible. If you're going to do this, I would recommend pulling at least from the feisty repo, as described in pupeno's blog, and in more detail in my other post linked above. Basically, this installs all ghc6* packages, with ad-hoc blocking of packages that cause aptitude to complain. The basic approach seems sound though. If it gets stuck at some point, I'll just add the offending package to the filter list. (I suspect there's a more intelligent way to do this if you know debian package management better than I do.) The script below has been cranking away for a pretty long time now -- so not only may your mileage vary, mine isnt' even yet. I also wouldn't recommend doing this on a production server. (When/if I hose my system, I can reload a virgin ubuntu in under five minutes using my linode control panel.) * apt-cache search libghc6 | ghc -e 'interact $ unlines . map (\l - head $ words l ) . lines' \ | grep -ivE \(ghc6-hopengl\|libghc6-c2hs-dev\) \ | xargs apt-get -y install 2007/3/16, Chad Scherrer [EMAIL PROTECTED]: Brian, I had this exact problem, and I found this approach to work wonderfully: http://pupeno.com/2006/12/17/unstable-packages-on-ubuntu/ Chad ___ 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[2]: [Haskell-cafe] Tracking characters and a timestamp ?
Hello Marc, Thursday, April 5, 2007, 8:40:04 AM, you wrote: Bulat: When also using unsafeInterleavedMapM for the second mapM the program will stop after processing the first list item. question 2 I can't see why this is the case. because there is no need to calculate entire answer before return. unsafeInterleavedMapM is written in the manner that only first list item will be obligatory calculated, all other only on demand :))) you definitely should read http://haskell.org/haskellwiki/IO_inside Continuation does work as well: this code is 100% equivalent of (mapM_ (c- ...)) proposed earlier -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re[2]: [Haskell-cafe] Automatic derivation (TemplateHaskell?)
Following tells me that Data.Derive.Peephole was built. ar t dist/build/libHSderive-0.1.a says Derive.o is there. ghc-pkg -l /opt/local/lib/ghc-6.6/package.conf: Cabal-1.1.6, FilePath-0.11, GLUT-2.0, HUnit-1.1, OpenGL-2.1, QuickCheck-1.0, base-2.0, cgi-2006.9.6, derive-0.1, fgl-5.2, (ghc-6.6), haskell-src-1.0, haskell98-1.0, html-1.0, mtl-1.0, network-2.0, parsec-2.0, readline-1.0, regex-base-0.71, regex-compat-0.71, regex-posix-0.71, rts-1.0, stm-2.0, template-haskell-2.0, time-1.0, unix-1.0, xhtml-2006.9.13 derive-1.0 is in the list of packages. ghc --make FunParser.hs FunParser.hs:4:7: Could not find module `Data.Derive.Peephole': Use -v to see a list of the files searched for. I'm baffled again. --- runhaskell Setup.hs build Preprocessing library derive-0.1... Preprocessing executables for derive-0.1... Building derive-0.1... [1 of 9] Compiling Data.Derive.FixedPpr ( Data/Derive/FixedPpr.hs, dist/build/Data/Derive/FixedPpr.o ) [2 of 9] Compiling Data.Derive ( Data/Derive.hs, dist/build/Data/ Derive.o ) [3 of 9] Compiling Data.Derive.SYB ( Data/Derive/SYB.hs, dist/build/ Data/Derive/SYB.o ) [4 of 9] Compiling Data.Derive.TH ( Data/Derive/TH.hs, dist/build/ Data/Derive/TH.o ) [5 of 9] Compiling Data.Derive.BinaryDefer ( Data/Derive/ BinaryDefer.hs, dist/build/Data/Derive/BinaryDefer.o ) [6 of 9] Compiling Data.Derive.Eq ( Data/Derive/Eq.hs, dist/build/ Data/Derive/Eq.o ) [7 of 9] Compiling Data.Derive.Peephole ( Data/Derive/Peephole.hs, dist/build/Data/Derive/Peephole.o ) [8 of 9] Compiling Data.Derive.Binary ( Data/Derive/Binary.hs, dist/ build/Data/Derive/Binary.o ) [9 of 9] Compiling Data.Derive.Play ( Data/Derive/Play.hs, dist/build/ Data/Derive/Play.o ) ar: creating archive dist/build/libHSderive-0.1.a [1 of 1] Compiling Main ( Derive.hs, dist/build/derive/ derive-tmp/Main.o ) Linking dist/build/derive/derive ... sudo runhaskell Setup.hs install Installing: /usr/local/lib/derive-0.1/ghc-6.6 /usr/local/bin derive-0.1... Registering derive-0.1... Reading package info from .installed-pkg-config ... done. Saving old package config file... done. Writing new package config file... done. -- http://wagerlabs.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Automatic derivation (TemplateHaskell?)
Stefan, What version of ghc are you using? Mine is 6.6. Data/Derive/Play.hs:9:7: Could not find module `Control.Monad.State': it is a member of package mtl-1.0, which is hidden I commented out that import line. Preprocessing library derive-0.1... Preprocessing executables for derive-0.1... Building derive-0.1... [1 of 9] Compiling Data.Derive.FixedPpr ( Data/Derive/FixedPpr.hs, dist/build/Data/Derive/FixedPpr.o ) [2 of 9] Compiling Data.Derive ( Data/Derive.hs, dist/build/Data/ Derive.o ) [3 of 9] Compiling Data.Derive.SYB ( Data/Derive/SYB.hs, dist/build/ Data/Derive/SYB.o ) [4 of 9] Compiling Data.Derive.TH ( Data/Derive/TH.hs, dist/build/ Data/Derive/TH.o ) Data/Derive/TH.hs:25:26: No instance for (Functor Q) arising from use of `fmap' at Data/Derive/TH.hs:25:26-31 Possible fix: add an instance declaration for (Functor Q) In the first argument of `(.)', namely `fmap f' In the expression: (fmap f) . deriveOne In the definition of `derive': derive (Derivation f _) = (fmap f) . deriveOne This I don't know how to deal with. Thanks, Joel -- http://wagerlabs.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Automatic derivation (TemplateHaskell?)
On Apr 5, 2007, at 11:04 AM, Joel Reymont wrote: This is in Language.Haskell.TH.Syntax which is imported at the top of Data/Derive/TH.hs so I don't understand the cause of the error Apparently instance Functor Q was added to 6.6 very recently and it's not in MacPorts yet. I decided to throw down the gauntlet and run 6.7 instead. -- http://wagerlabs.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Trouble trying to find packages for ubuntu linux
On 05/04/07, Thomas Hartman [EMAIL PROTECTED] wrote: In the spirit of... I hate package chasing, cabal doesn't do this automatically (yet), and hard disk space is cheap... Agreed. As much as I like the rest of Ubuntu I'm beginning to dislike binary packages after only a week away from Gentoo ;-) Still, at least they install quicker! Are there recommended ways of setting up current development systems? I'm the only person on this machine, so having system-wide packages isn't much of an issue. Would I be better just building all my own from tarball rather than hoping Feisty stays up to date? Cheers, D. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Automatic derivation (TemplateHaskell?)
That did it, thanks! On Apr 5, 2007, at 12:07 PM, Twan van Laarhoven wrote: instance Functor Q where fmap = liftM -- http://wagerlabs.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re[2]: [Haskell-cafe] Automatic derivation (TemplateHaskell?)
Installed derive, trying to load it with ghci -package derive Loading package base ... linking ... done. Loading package template-haskell ... linking ... done. Loading package FilePath-0.11 ... linking ... done. ghc-6.6: unknown symbol `_derivezm0zi1_DataziDeriveziPeephole_zdf7_closure' Loading package derive-0.1 ... linking ... ghc-6.6: unable to load package `derive-0.1' What am I doing wrong? Thanks, Joel -- http://wagerlabs.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Automatic derivation (TemplateHaskell?)
Joel Reymont wrote: This is in Language.Haskell.TH.Syntax which is imported at the top of Data/Derive/TH.hs so I don't understand the cause of the error instance Functor Q where fmap f (Q x) = Q (fmap f x) ... Any suggestions? Since Q is a Monad, you can make the instance instance Functor Q where fmap = liftM But Q is exported by Languave.Haskell.TH.Syntax !!! Only the type constructor is exported, not the data constructor. Twan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Automatic derivation (TemplateHaskell?)
This is in Language.Haskell.TH.Syntax which is imported at the top of Data/Derive/TH.hs so I don't understand the cause of the error instance Functor Q where fmap f (Q x) = Q (fmap f x) Copying the above into TH.hs gives me Preprocessing library derive-0.1... Preprocessing executables for derive-0.1... Building derive-0.1... [4 of 9] Compiling Data.Derive.TH ( Data/Derive/TH.hs, dist/build/ Data/Derive/TH.o ) Data/Derive/TH.hs:23:10: Not in scope: data constructor `Q' Data/Derive/TH.hs:23:17: Not in scope: data constructor `Q' But Q is exported by Languave.Haskell.TH.Syntax !!! Any suggestions? Thanks, Joel -- http://wagerlabs.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Automatic derivation (TemplateHaskell?)
Joel Reymont wrote:
Folks,
I have very uniform Parsec code like this and I'm wondering if I can
derive it using TemplateHaskell or DrIFT or some other tool. Any ideas?
Others have given good answers on how to use code-generation. I am more
interested in whether code generation is actually necessary for this
example. Haskell has good data-manipulation tools, and parsers are a
kind of data...
First of all, the nullary commands. Here is an abbreviated version with
only them:
strCall =
choice [ do { reserved NewLine
; return NewLine
}
, do { reserved GetSymbolName
; return GetSymbolName
}
, do { reserved Description
; return Description
}
, do { reserved GetExchangeName
; return GetExchangeName
}
, do { reserved SymbolRoot
; return SymbolRoot
}
]
The 'do' syntax is unpleasantly verbose for such simple examples. As a
guideline, I personally only use 'do' syntax if there is at least one
result to 'capture' (bind) and use elsewhere. Already the code is easier
to read if we do something like this:
strCall =
choice [ reserved NewLine return NewLine
, reserved GetSymbolNamereturn GetSymbolName
, reserved Description return Description
, reserved GetExchangeName return GetExchangeName
, reserved SymbolRoot return SymbolRoot
]
Now this we can make simpler with the very basic 'metaprogramming' built
into the 'deriving Show' that haskell has:
nullary x = reserved (show x) return x
strCall = choice ( map nullary
[NewLine,GetSymbolName,Description,GetExchangeName,SymbolRoot] )
To do the same for unaries, we need to know which kind of parameter to
expect.
data paramType = JNum | JBool | JStr
paramParser JNum = numExpr
paramParser JBool = boolExpr
paramParser JStr = strExpr
unary x pt = reserved (quasiShow (x undefined)) parens (paramParser
pt) = return . x
strCall = choice ( map unary
[ELDateToString,TextGetString,LowerStr,UpperStr,Spaces] )
But what is 'quasiShow'? This is the function which maps these
constructors to their string representation, without inspecting the
argument (so I can safely pass undefined). This perhaps you do need
meta-programming for. Although, I think you can write the following:
quasiShow = takeWhile (/=' ') . show
Feels a bit ugly though :)
And now binaries are only slightly more complex (but now I will use 'do'
notation):
binary x pta ptb = reserved (quasiShow x undefined undefined)
parens $ do a - paramParser pta
comma
b - paramParser ptb
return x a b
I'm sure you can work out ternaries.
Of course if you want to automatically choose binary, ternary or unary
from the definition of the ADT then you're thoroughly back into the
world of metaprogramming.
The purpose of this message was not to discourage you from
metaprogamming, which is a powerful tool, but just to show that haskell
is capable of many things which in other languages would be
metaprogramming, either entirely without a meta part, or just using the
limited built in meta-facilities (i.e. derived instances).
Jules
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Re: Re[2]: [Haskell-cafe] Automatic derivation (TemplateHaskell?)
This is the exposed modules portion of derive.cabal. I had to remove the empty lines since Cabal was complaining about them. I suspect one of these lines had Data.Derive.Peephole in it. Exposed-Modules: Data.Derive Data.Derive.FixedPpr Data.Derive.SYB Data.Derive.TH Data.Derive.Binary Data.Derive.BinaryDefer Data.Derive.Eq Data.Derive.Play On Apr 5, 2007, at 12:46 PM, Joel Reymont wrote: FunParser.hs:4:7: Could not find module `Data.Derive.Peephole': Use -v to see a list of the files searched for. -- http://wagerlabs.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Automatic derivation (TemplateHaskell?)
Jules Bean wrote: data paramType = JNum | JBool | JStr paramParser JNum = numExpr paramParser JBool = boolExpr paramParser JStr = strExpr unary x pt = reserved (quasiShow (x undefined)) parens (paramParser pt) = return . x strCall = choice ( map unary [ELDateToString,TextGetString,LowerStr,UpperStr,Spaces] ) Oops. unary (x,pt) = reserved (quasiShow (x undefined)) parens (paramParser pt) = return . x strCall = choice ( map unary [(ELDateToString,JNum),(TextGetString,JNum), (LowerStr,JStr),(UpperStr,JStr),(Spaces,JStr)] ) (have to specify the param types) Jules ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Type classes to 'reflect' constructor structure
In the thread 'automatic derivation', Joel Reymont is looking for
metaprogramming functionality with which he wants to automatically
derive a parser and a pretty printer for his ADT (which is an AST for a
minilanguage).
I replied showing that a significant amount of the boilerplate could be
removed anyway just using haskell's built in ability to process parsers
as 'data'. I could completely automate the nullary constructions, but I
needed type information for n-ary ones.
A bit of poking around with typeclasses showed a proof-of-concept for
getting the type-checker to extract that information for us:
{-# OPTIONS -fglasgow-exts #-}
import Data.Typeable
-- Stage 1 is just counting the arguments
class CountArgs s where numArgs :: s - Integer
data TestType = Nullary | Unary Int | Binary Int String
| OtherBinary String Int
instance CountArgs TestType where numArgs x = 0
instance CountArgs (a-TestType) where numArgs x = 1
instance CountArgs (a-b-TestType) where numArgs x = 2
-- *Main numArgs Nullary
-- 0
-- *Main numArgs Unary
-- 1
-- *Main numArgs Binary
-- 2
-- Stage 2 actually lists the types of the arguments
-- I'll use a seperate ADT to make the types concrete
data ArgTypes = JInt | JStr deriving (Show)
class ConcreteType t where makeAT :: t - ArgTypes
instance ConcreteType Int where makeAT _ = JInt
instance ConcreteType String where makeAT _ = JStr
class DescribeArgs s where descArgs :: s - [ArgTypes]
instance DescribeArgs TestType where descArgs _ = []
instance ConcreteType a = DescribeArgs (a-TestType)
where descArgs _ = [makeAT (undefined::a)]
instance (ConcreteType a, ConcreteType b) =
DescribeArgs (a-b-TestType)
where descArgs _ = [makeAT (undefined::a), makeAT (undefined::b)]
-- *Main descArgs Nullary
-- []
-- *Main descArgs Unary
-- [JInt]
-- *Main descArgs Binary
-- [JInt,JStr]
-- *Main descArgs OtherBinary
-- [JStr,JInt]
-- Stage 3 is just the Data.Typeable version of the stage 2
class DescribeArgs2 s where descArgs2 :: s - [TypeRep]
instance DescribeArgs2 TestType where descArgs2 _ = []
instance Typeable a = DescribeArgs2 (a-TestType)
where descArgs2 _ = [typeOf (undefined::a)]
instance (Typeable a, Typeable b) =
DescribeArgs2 (a-b-TestType)
where descArgs2 _ = [typeOf (undefined::a), typeOf (undefined::b)]
-- *Main descArgs2 Nullary
-- []
-- *Main descArgs2 Unary
-- [Int]
-- *Main descArgs2 Binary
-- [Int,[Char]]
-- *Main descArgs2 OtherBinary
-- [[Char],Int]
There are still some things this approach fails on: it can't give you a
complete list of all constructors of TestType, for example. (Such a list
would necessarily an existential type, like [exists x . DescribeArgs x
- x]).
I'm sure my thoughts aren't original. Have other people taken this
further into interesting directions? Where is the line beyond which you
need 'true' metaprogramming?
Jules
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Re: [Haskell-cafe] Automatic derivation (TemplateHaskell?)
With derive compiled and installed I thought I would change the code
a bit and try it...
ghci -fth -v0 -e '$( _derive_print_instance makeFunParser
Foo )' baz.hs
baz.hs:30:3: Not in scope: `a1'
Any help is appreciated!
Thanks, Joel
---
FunParser.hs:
module FunParser where
import Data.Derive
import Data.Derive.Peephole
import Data.List
import Text.ParserCombinators.Parsec ( CharParser )
makeFunParser = Derivation drv FunParser
drv dat@(DataDef name arity ctors) =
simple_instance FunParser dat [funN parse [ sclause [] body ] ]
where
body = l1 choice $ lst [ clause con | con - ctors ]
clause con = l1 reserved (lit (trim (ctorName con)))
: args con (ctorArity con)
trim = reverse . takeWhile (/= '.') . reverse
args ct 0 = return' (ctp ct 'a')
args ct k = l1 char (lit '(') : args' ct k 0
args' ct remn seen = l0 parse
=: (('a' : show seen)
-: args'' ct (remn-1) (seen+1))
args'' ct 0 seen = l1 char (lit ')') : return' (ctp ct 'a')
args'' ct k seen = l1 char (lit ',') : args' ct k seen
class FunParser a
where parse :: CharParser s a
baz.hs:
import Text.ParserCombinators.Parsec hiding ( parse )
import qualified Text.ParserCombinators.Parsec.Token as T
import Text.ParserCombinators.Parsec.Language( emptyDef )
import Data.Derive.TH
import FunParser
data NumExpr
= Int Integer
| Num Double
instance FunParser NumExpr where
parse = numExpr
data Foo
= Foo NumExpr
lexer = T.makeTokenParser emptyDef
identifier = T.identifier lexer
reserved = T.reserved lexer
integer = T.integer lexer
float = T.float lexer
numExpr :: GenParser Char a NumExpr
numExpr =
choice [ integer = return . Int
, float = return . Num
]
$( derive makeFunParser ''Foo )
--
http://wagerlabs.com/
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Re: [Haskell-cafe] Automatic derivation (TemplateHaskell?)
Here's the output from -ddump-splices (thanks Saizan for the tip).
It's returning a1 instead of a0.
ghci -fth -e '$( _derive_print_instance makeFunParser Foo )'
baz.hs -ddump-splices
baz.hs:1:0:
baz.hs:1:0: Splicing declarations
derive makeFunParser 'Foo
==
baz.hs:30:3-28
instance {FunParser Main.Foo} where
[]
{ parse = choice
[()
(reserved ['F', 'o', 'o'])
(()
(char '(') ((=) parse (\ a0 - ()
(char ')') (return (Main.Foo a1)] }
baz.hs:30:3: Not in scope: `a1'
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Re: Re[2]: [Haskell-cafe] `Expect'-like lazy reading/Parsec matching on TCP sockets
Bulat, yes, with both variants. actually, second one should be easier to implement and understand. you should look into unsafeInterleaveIO section of http://haskell.org/haskellwiki/IO_inside This seems to do what I want, and unless I'm overlooking something it feels very straight-forward: hGetContentsTimeout :: Handle - Int - IO String hGetContentsTimeout h t = do hSetBuffering stdin NoBuffering ready - hWaitForInput h t if (not ready) then return [] else do c - hGetChar h s - unsafeInterleaveIO (hGetContentsTimeout h t) return (c:s) This is not extensivly tested, but applying my parser to the string returned by hGetContentsTimeout behaves precisely as I wanted: It returns a match as soon as it is available, and fails if it is not seen within t ms. Thanks for your help! - Scott ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Automatic derivation (TemplateHaskell?)
On Thu, Apr 05, 2007 at 02:47:21PM +0100, Joel Reymont wrote:
Here's the output from -ddump-splices (thanks Saizan for the tip).
It's returning a1 instead of a0.
ghci -fth -e '$( _derive_print_instance makeFunParser Foo )'
baz.hs -ddump-splices
baz.hs:1:0:
baz.hs:1:0: Splicing declarations
derive makeFunParser 'Foo
==
baz.hs:30:3-28
instance {FunParser Main.Foo} where
[]
{ parse = choice
[()
(reserved ['F', 'o', 'o'])
(()
(char '(') ((=) parse (\ a0 - ()
(char ')') (return (Main.Foo a1)] }
baz.hs:30:3: Not in scope: `a1'
Sorry for the late multiple reply, I just spent seven hours sleeping...
I am not the maintainer of Data.Derive, nor did I write the majority
of the nice code; Neil Mitchell did it, you can ask him why replace
DrIFT. However, using abstract syntax trees WAS my idea.
First, _derive_print_instance will never give you a TH splice error,
since it always evaluates to an empty list of declarations. It uses
the TH 'runIO' facility such that type-checking a file using
_derive_print_instance will emit the instances to standard output as a
side effect. So the error is coming from the $(derive) in baz.hs, if
you have more errors try commenting it out. (you'll get bogus code on
stdout, but at least it will be completly haskell!)
_derive_print_instance was not intended to be a debugging aid,
although it certainly works well in that capacity. The intent is that
it will be used when the standalone driver is rewritten to use TH,
which I intend to do not long after I can (Neil is out of
communication for a week with intent to continue hacking Derive; I'm
taking this as a repository lock).
Yes, we do use type classes to implement recursion across types. This
seems to be a very standard idiom in Haskell, used by Show, Read, Eq,
Ord, NFData, Arbitrary, and doubtless many more.
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Re: [Haskell-cafe] What I learned from my first serious attempt low-level Haskell programming
On Thu, Apr 05, 2007 at 02:50:49PM +0400, Bulat Ziganshin wrote: Hello Stefan, Thursday, April 5, 2007, 3:11:31 AM, you wrote: 2. Parameters are very expensive. you should look at the asm code GHC generates. afair parameters are kept in stack and copied on each call (to the same place!). such sort of things are also very dependent on backend used - was it a ASM or C one? Yes, I will update the wiki. ghc -O2, where [EMAIL PROTECTED]:~$ ghc -V The Glorious Glasgow Haskell Compilation System, version 6.7.20070402 [EMAIL PROTECTED]:~$ uname -a Linux stefans 2.6.18-3-686 #1 SMP Sun Dec 10 19:37:06 UTC 2006 i686 GNU/Linux [EMAIL PROTECTED]:~$ cpuid eax ineax ebx ecx edx 0002 756e6547 6c65746e 49656e69 0001 0f24 00010809 3febfbff 0002 665b5001 007b7040 8000 8004 8001 8002 20202020 20202020 20202020 6e492020 8003 286c6574 50202952 69746e65 52286d75 8004 20342029 20555043 30302e32 007a4847 Vendor ID: GenuineIntel; CPUID level 2 Intel-specific functions: Version 0f24: Type 0 - Original OEM Family 15 - Pentium 4 Extended family 0 Model 2 - Stepping 4 Reserved 0 Brand index: 9 [not in table] Extended brand string: Intel(R) Pentium(R) 4 CPU 2.00GHz CLFLUSH instruction cache line size: 8 Hyper threading siblings: 1 Feature flags 3febfbff: FPUFloating Point Unit VMEVirtual 8086 Mode Enhancements DE Debugging Extensions PSEPage Size Extensions TSCTime Stamp Counter MSRModel Specific Registers PAEPhysical Address Extension MCEMachine Check Exception CX8COMPXCHG8B Instruction APIC On-chip Advanced Programmable Interrupt Controller present and enabled SEPFast System Call MTRR Memory Type Range Registers PGEPTE Global Flag MCAMachine Check Architecture CMOV Conditional Move and Compare Instructions FGPAT Page Attribute Table PSE-36 36-bit Page Size Extension CLFSH CFLUSH instruction DS Debug store ACPI Thermal Monitor and Clock Ctrl MMXMMX instruction set FXSR Fast FP/MMX Streaming SIMD Extensions save/restore SSEStreaming SIMD Extensions instruction set SSE2 SSE2 extensions SS Self Snoop HT Hyper Threading TM Thermal monitor TLB and cache info: 50: Instruction TLB: 4KB and 2MB or 4MB pages, 64 entries 5b: Data TLB: 4KB and 4MB pages, 64 entries 66: 1st-level data cache: 8KB, 4-way set assoc, 64 byte line size 40: No 2nd-level cache, or if 2nd-level cache exists, no 3rd-level cache 70: Trace cache: 12K-micro-op, 4-way set assoc 7b: 2nd-level cache: 512KB, 8-way set assoc, sectored, 64 byte line size Stefan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Parsing unordered parameter list with Parsec
Hi all, I'm new to Haskell and trying to do some parsing with Parsec. It's been extremely good so far. I have run into a problem I can't seem to see the solution to though. I hope someone on the list can help me out! I have a command with a parameter list like this: CMD PARAM1 foo PARAM2 100 PARAM3 200 Which is easy enough to parse, but it turns out the grammar is not particularly well defined, and it's considered acceptable to swap parameter order round pretty much arbitrarily. Is there a simple way to handle this? I would like to only allow one of each parameter, some parameters may also be optional. It feels like I might have to write my own combinator to do this but I'm not sure I'm quite ready of that yet! Thanks, ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re[2]: [Haskell-cafe] Tracking characters and a timestamp ?
On 4/5/07, Bulat Ziganshin [EMAIL PROTECTED] wrote: you definitely should read http://haskell.org/haskellwiki/IO_inside Thanks for mentioning this link -- I wasn't aware of it. I wish it existed when I first started learning Haskell... -- Rich AIM : rnezzy ICQ : 174908475 Jabber: [EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Automatic derivation (TemplateHaskell?)
On Thu, Apr 05, 2007 at 03:19:15PM +0100, Joel Reymont wrote: numExpr :: GenParser Char a NumExpr numExpr = choice [ integer = return . Int , float = return . Num ] Parsec's choice operator works by parsing the first, and only parsing the second if the first fails immediately. So, given the input 123.456: - Parsec parses 'integer = return . Int' - this is successful - numExpr returns (Int 123, .456) - we try to match . against ) and fail. The fix is to left-factor the grammar, or just use the existing factored choice operator: numExpr :: GenParser Char a NumExpr numExpr = do sg - lexeme sign nf - natOrFloat return $ either (Int . sg) (Nat . sg) nf It seems silly that there is no signed version of natOrFloat predefined, any Parsec experts? Stefan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Automatic derivation (TemplateHaskell?)
Shouldn't this work just as well? numExpr = choice [ try $ float = return . Num , integer = return . Int ] It works on Foo(10.345) but not on Bar(10, 103.34). On Apr 5, 2007, at 4:09 PM, Stefan O'Rear wrote: numExpr :: GenParser Char a NumExpr numExpr = do sg - lexeme sign nf - natOrFloat return $ either (Int . sg) (Nat . sg) nf It seems silly that there is no signed version of natOrFloat predefined, any Parsec experts? Stefan -- http://wagerlabs.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Automatic derivation (TemplateHaskell?)
On Wed, Apr 04, 2007 at 04:48:56PM -0700, Stefan O'Rear wrote: Data.Derive can do this. In an attempt to avoid munging the relevent files they are attached. You might want to note that DrIFT used to be called derive before it (amicably) changed its name due to a conflict with a product of the same name. John -- John Meacham - ⑆repetae.net⑆john⑈ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Short-circuiting a fold
On 05/04/07, Kurt Hutchinson [EMAIL PROTECTED] wrote: Straightforward: ssfold p f z = head . dropWhile ( not . p ) . scanl f z I'd prefer find instead of head . dropWhile (not . p), making the result type a Maybe, as this is essentially equivalent to searching through the result of a scan for a specific value, so it should follow find's example and use Maybe for its partiality. I want to see some real creativity here, so pull out all the stops. You may also be interested in the Compose experiment [1]: a bit of fun seeing how many different ways compose :: [a - a] -(a - a) could be defined. Most are quite silly, but the solution involving the State monad, for example, is really quite elegant. [1]: http://haskell.org/haskellwiki/Compose -- -David House, [EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Short-circuiting a fold
On Thu, Apr 05, 2007 at 02:09:12PM -0400, Kurt Hutchinson wrote:
Here's a bit of Thursday afternoon fun.
Mission:
Define ssfold, a short-circuiting fold. It evaluates to the folded
value that first satisfies the given predicate.
ssfold :: ( a - Bool ) - ( a - b - a ) - a - [b] - a
Here are two of mine.
Straightforward:
ssfold p f z = head . dropWhile ( not . p ) . scanl f z
Monadic:
data Done a b = Done { undone :: a } | NotDone b
instance Monad ( Done a ) where
( NotDone i ) = f = f i
( Doner ) = _ = Done r
return = NotDone
ssfold p f z = undone . foldM (\ v e - if p v then Done v else NotDone (
f v e ) ) z
ssfold p f z = fromJust . find p . scanl f z
-- might need a few (safe) unsafeCoerce#s
ssfold p f z = go . (z:) where
go (x:xs) | p x = x
| otherwise = case xs of (xx:xxs) - go (f x xx:xxs)
ssfold p f z = go z where
go a xs | xs `seq` p a = a
| otherwise = case xs of (xx:xxs) - go (f x xx) xxs
ssfold p f z = foldr go (\k - if p k then k else undefined) where
go ths cont acc | p acc = acc
| otherwise = cont (f acc ths)
data Exit = Exit Any deriving Typeable
ssfold p f z l = unsafePerformIO $ catchDyn (evaluate (go l z)) (\ (Exit a) -
return $ unsafeCoerce# a)
where go l ac | p ac = throwDyn (Exit (unsafeCoerce# ac))
go (x:xs) ac = go xs (f ac x)
Stefan
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[Haskell-cafe] Re: [web-devel] A light-weight web framework
The maintenance nightmare happens when someone uses the embedded language to
specify business logic, and that's entirely the web-{developer,designer}'s
fault. Thus, the problem is not that these languages shouldn't be powerful
enough.
IMHO, a safe approach would be simply not allowing I/O inside templates
(hey, sounds familiar ;-)
On 4/5/07, Maurice Codik [EMAIL PROTECTED] wrote:
A few things, some of which I sort of mentioned in my previous email:
- If I'm already going to commit some time to learn a templating language,
why dont I just spend that same amount of time learning the little bit of
haskell I need to make the template work? If thats too much to ask, I can
just spit out HTML, and have the programmer put in the dynamic parts for me.
Both of these scenarios seem to be a more efficient use of time.
- Who is the target audience? If its a big organization where there are
multiple designers and multiple devs, then your approach may work just fine.
If its the single developer, then something like what David suggested would
work even better. If its a small team (which may or may not include a
full-time designer), then something like what I suggested would work best.
For a web framework for haskell, I would guess that the latter two are much
more likely.
- Embedding a real programming language in a template already gives you
power to do what ever you need to do. What if you need to implement some
logic that the template language doesnt support? In those cases, you're
usually out of luck and have to move that logic into a controller, where it
doesnt really belong (assuming its actual display logic, not business
logic).
- It's really just a matter of taste. Any web framework thats worth using
should be flexible in its support of view technologies, but come with one
thats a sensible default.
Maurice
On 4/5/07, Joel Reymont [EMAIL PROTECTED] wrote:
Do you see anything wrong with the approach I suggested, though?
On Apr 5, 2007, at 6:16 PM, Maurice Codik wrote:
That's not necesarily true. Templates where there is mostly markup,
but let you embed code into them using special tags (ex, % code %
) are extremely popular and work fairly well. They also keep the
template language simple because there is already a full-powered
programming language thats embedded into it. Good examples of this
method are ERB templates in Rails, JSPs, Perl Mason templates, etc.
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Any sufficiently complicated C or Fortran program contains an ad hoc,
informally specified, bug-ridden, slow implementation of half of Common
Lisp
Any sufficiently complicated Lisp or Ruby program contains an ad hoc,
informally-specified, bug-ridden, slow implementation of half of Haskell
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Re: [Haskell-cafe] Re: What I learned from my first serious attempt low-level Haskell programming
It's not that hard to figure out an order to permute the arguments on the stack before a tail call that minimizes that number of moves and temporary locations. Lmlc did this 20 years ago. :) -- Lennart On Apr 5, 2007, at 19:17 , Claus Reinke wrote: Stefan O'Rear wrote: 2. Parameters are very expensive. Our type of functions that build (ignoring CPS for the time being) was MBA# - Int# - [ByteString], where the Int# is the current write pointer. Adding an extra Int# to cache the size of the array (rather than calling sMBA# each time) slowed the code down ~2x. Conversely, moving the write pointer into the byte array (storing it in bytes 0#, 1#, 2#, and 3#) sped the code by 4x. If you were measuring on x86 then parameters are passed on the stack, which may be expensive. On x86_64 the first 3 arguments are passed in registers, which is usually a win, but if the function immediately does an eval they need to be saved on the stack anyway. Still, 4x sounds like a lot, perhaps you managed to avoid a stack check in the inner loop or something. just out of curiosity: what does GHC do with stack parameters in loops/tail calls? there tends to be a conflict as the old set of parameters is needed to build the new one for the recursive call/next loop iteration, while one wants to get rid of the old set before doing the call. unless one keeps the parameter frames away from the stack, or can figure out a safe order in which to overwrite the parameters in the frame, that seems to imply some copying, even though that may be cheap for few/small parameters per frame. many years ago, i saw an abstract machine and RISC processor design aiming for good fp support that used two parameter stacks instead of one for just this reason. instead of moving stack frames around on a single stack, parameters were read from one stack, and built up on the other, followed by a cheap stack switch before the call. perhaps something like this might be of use here, too? claus ___ Libraries mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/libraries ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: Atom - Yet another Haskell HDL
It's great to see the Bluespec ideas cast in Haskell syntax again. Bluspec Inc has strayed from that path, I'm afraid. -- Lennart On Apr 4, 2007, at 05:18 , Tom Hawkins wrote: Hi, Haskell has a rich history of embedded hardware description languages. Here's one more for the list. Inspired by the work of Arvind, Hoe, and all the sharp folks at Bluespec, Atom is a small HDL that compiles conditional term rewriting systems down to Verilog RTL. In Atom, a circuit description is composed of a set of state elements (registers) and a set of rules. Each rule has two components: an enabling condition and a collection of actions, or state updates. When a rule is enabled, it's actions may be selected to execute atomically. In contrast to Verilog always blocks, multiple rules can write to the same state element. Here's an enabled counter in Atom: counter :: Int - Signal - System Signal counter width enable = do count - reg count width 0 rule updateCount $ do when enable count == value count +. one width return $ value count Enjoy! http://funhdl.org/ -Tom A few details: The Atom compiler attempts to maximize the number of rules that can execute in a given clock cycle without breaking the semantics of one-rule-at-a-time. For simplicity, rules are assigned a global, linear priority. Data dependencies between rules form a graph. A acyclic graph is ideal, because all rules become sequentially composable. The compiler attempts to order the rules to minimize the number of edges feeding back from lower to higher priority rules. This is equivalent to the feedback arc set problem. (Atom's FAS optimization is pretty poor at the moment.) In a rule-data dependency graph, many of the edges are irrelevent because pairs of rules are often mutually exclusive, ie. can not be enabled at the same time. MiniSat is used to hunt and prune edges from mutually exclusive rules. By only looking back to primary inputs and registers, the SAT procedure is not guaranteed to find all mutually exclusive rules, but it does a pretty good job. ___ 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
