Re: [Haskell-cafe] "import" functionality in DSLs
On Sat, Apr 16, 2011 at 13:49 CDT, Luke Palmer wrote:
> You can get away with this using {-# LANGUAGE RecordWildCards #-}, if you
> put your prelude into a record. Here's a test I did to make sure the
> technique worked:
>
> {-# LANGUAGE RecordWildCards #-}
>
> import Prelude hiding ((+))
>
> data Foo = Foo {
> (+) :: Int -> Int -> Int,
> n0 :: Int
> }
>
> prelude :: IO Foo
> prelude = return $ Foo { (+) = (*), n0 = 1 }
>
> doit :: IO Int
> doit = do
> Foo{..} <- prelude
> return $ n0 + 3 + 4
Oh, that's pretty sweet! Thank you very much! :)
nikhil
>
>
> ghci> doit
> 12
>
> On Sat, Apr 16, 2011 at 7:29 AM, Nikhil A. Patil
> wrote:
>
> > Hi,
> >
> > I am planning a simple monadic DSL (frankly, calling it a DSL is a bit
> > of a stretch; it's just a somewhat glorified state monad), and I wish to
> > implement some kind of "import" functionality for it.
> >
> > The DSL code looks something like this:
> >
> > > doit :: DSL Term
> > > doit = do (+) <- define_function "+" 2
> > > n0 <- define_constant "0"
> > > k <- define_constant "k"
> > > -- begin beautiful DSL code
> > > let x = k + n0
> > > return $ x + x
> >
> > The code above adds identifiers "+", "0", "k" to the DSL monad and
> > conveniently exposes haskell identifiers (+), n0, k for the user to use
> > in code that follows. (Note that these define_* functions make state
> > updates in the underlying state monad.)
> >
> > Needless to say, most functions like doit have very similar define_*
> > calls in the beginning. Thus, I want to implement some kind of import
> > functionality. Ideally, the code would look like this:
> >
> > > module DSLPrelude where
> > >
> > > prelude :: DSL ()
> > > prelude = do (+) <- define_function "+" 2
> > > n0 <- define_constant "0"
> > > k <- define_constant "k"
> > > return ()
> >
> > > module Main where
> > > import DSLPrelude
> > >
> > > doit :: DSL Term
> > > doit = do prelude
> > > -- begin beautiful DSL code
> > > let x = k + n0
> > > return $ x + x
> >
> > ...but of course that won't work since (+), n0, k are not in scope.
> >
> > I can think of two solutions, both of which I dislike:
> >
> > Solution 1:
> >
> > > module DSLPrelude where
> > >
> > > prelude :: DSL (Term -> Term -> Term, Term, Term)
> > > prelude = do (+) <- define_function "+" 2
> > > n0 <- define_constant "0"
> > > k <- define_constant "k"
> > > return ((+), n0, k)
> >
> > > module Main where
> > > import DSLPrelude
> > >
> > > doit :: DSL Term
> > > doit = do ((+), k, n0) <- prelude
> > > -- begin beautiful DSL code
> > > let x = k + n0
> > > return $ x + x
> >
> > This is quite unsafe: I have mistakenly swapped k and n0 in doit,
> > without failing typecheck.
> >
> > Solution 2:
> >
> > > module DSLPrelude where
> > >
> > > (+) :: DSL (Term -> Term -> Term)
> > > n0 :: DSL Term
> > > k :: DSL Term
> > > (+) = define_function "+" 2
> > > n0 = define_constant "0"
> > > k = define_constant "k"
> >
> > > module Main where
> > > import DSLPrelude
> > >
> > > doit :: DSL Term
> > > doit = do (+) <- (+)
> > > n0 <- n0
> > > k <- k
> > > -- begin beautiful DSL code
> > > let x = k + n0
> > > return $ x + x
> >
> > ...which works, but still has quite a bit of boilerplate crap.
> >
> > I feel this would be a common problem with a lot of DSLs, so I am
> > curious to know how others solve it. Any pointers and suggestions are
> > most welcome and greatly appreciated.
> >
> > Thanks!
> >
> > nikhil
> >
> > ___
> > Haskell-Cafe mailing list
> > Haskell-Cafe@haskell.org
> > http://www.haskell.org/mailman/listinfo/haskell-cafe
> >
___
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Re: [Haskell-cafe] "import" functionality in DSLs
You can get away with this using {-# LANGUAGE RecordWildCards #-}, if you
put your prelude into a record. Here's a test I did to make sure the
technique worked:
{-# LANGUAGE RecordWildCards #-}
import Prelude hiding ((+))
data Foo = Foo {
(+) :: Int -> Int -> Int,
n0 :: Int
}
prelude :: IO Foo
prelude = return $ Foo { (+) = (*), n0 = 1 }
doit :: IO Int
doit = do
Foo{..} <- prelude
return $ n0 + 3 + 4
ghci> doit
12
On Sat, Apr 16, 2011 at 7:29 AM, Nikhil A. Patil wrote:
> Hi,
>
> I am planning a simple monadic DSL (frankly, calling it a DSL is a bit
> of a stretch; it's just a somewhat glorified state monad), and I wish to
> implement some kind of "import" functionality for it.
>
> The DSL code looks something like this:
>
> > doit :: DSL Term
> > doit = do (+) <- define_function "+" 2
> > n0 <- define_constant "0"
> > k <- define_constant "k"
> > -- begin beautiful DSL code
> > let x = k + n0
> > return $ x + x
>
> The code above adds identifiers "+", "0", "k" to the DSL monad and
> conveniently exposes haskell identifiers (+), n0, k for the user to use
> in code that follows. (Note that these define_* functions make state
> updates in the underlying state monad.)
>
> Needless to say, most functions like doit have very similar define_*
> calls in the beginning. Thus, I want to implement some kind of import
> functionality. Ideally, the code would look like this:
>
> > module DSLPrelude where
> >
> > prelude :: DSL ()
> > prelude = do (+) <- define_function "+" 2
> > n0 <- define_constant "0"
> > k <- define_constant "k"
> > return ()
>
> > module Main where
> > import DSLPrelude
> >
> > doit :: DSL Term
> > doit = do prelude
> > -- begin beautiful DSL code
> > let x = k + n0
> > return $ x + x
>
> ...but of course that won't work since (+), n0, k are not in scope.
>
> I can think of two solutions, both of which I dislike:
>
> Solution 1:
>
> > module DSLPrelude where
> >
> > prelude :: DSL (Term -> Term -> Term, Term, Term)
> > prelude = do (+) <- define_function "+" 2
> > n0 <- define_constant "0"
> > k <- define_constant "k"
> > return ((+), n0, k)
>
> > module Main where
> > import DSLPrelude
> >
> > doit :: DSL Term
> > doit = do ((+), k, n0) <- prelude
> > -- begin beautiful DSL code
> > let x = k + n0
> > return $ x + x
>
> This is quite unsafe: I have mistakenly swapped k and n0 in doit,
> without failing typecheck.
>
> Solution 2:
>
> > module DSLPrelude where
> >
> > (+) :: DSL (Term -> Term -> Term)
> > n0 :: DSL Term
> > k :: DSL Term
> > (+) = define_function "+" 2
> > n0 = define_constant "0"
> > k = define_constant "k"
>
> > module Main where
> > import DSLPrelude
> >
> > doit :: DSL Term
> > doit = do (+) <- (+)
> > n0 <- n0
> > k <- k
> > -- begin beautiful DSL code
> > let x = k + n0
> > return $ x + x
>
> ...which works, but still has quite a bit of boilerplate crap.
>
> I feel this would be a common problem with a lot of DSLs, so I am
> curious to know how others solve it. Any pointers and suggestions are
> most welcome and greatly appreciated.
>
> Thanks!
>
> nikhil
>
> ___
> Haskell-Cafe mailing list
> Haskell-Cafe@haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe
>
___
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Re: [Haskell-cafe] Haskell Platform 2011.2.0.1 now available
On Fri, Apr 15, 2011 at 11:50 PM, Joachim Breitner wrote: > Hi, > > Am Freitag, den 15.04.2011, 15:44 -0700 schrieb Don Stewart: >> We're pleased to announce the 2011.2.0.1 release of the Haskell Platform: >> a single, standard Haskell distribution for everyone. >> >> Download the Haskell Platform 2011.2.0.1: >> >> http://haskell.org/platform/ > > or use Debian unstable, which ships this version of the platform since > five days already: http://people.debian.org/~nomeata/platform.html Good work! Is the link to Debian on the http://haskell.org/platform homepage correct? > * We only ship it already because the file on > http://code.galois.com/darcs/haskell-platform/haskell-platform.cabal > has already changed earlier, which was linked by > http://hackage.haskell.org/platform/changelog.html so we thought this is > already official and released and we just missed the announcement. Do you watch the haskell-platf...@projects.haskell.org mailing list? There we announced the freeze, and the initial release candidates. > Maybe it would be better if released versions get their own, static > directory again, as it was the case for > http://hackage.haskell.org/platform/2010.1.0.0/haskell-platform.cabal > and > http://hackage.haskell.org/platform/2010.2.0.0/haskell-platform.cabal Good idea. > and the relationship between the repositories > http://code.haskell.org/haskell-platform/ and > http://code.galois.com/darcs/haskell-platform/ should be explained on > http://trac.haskell.org/haskell-platform/. That's just a temporary problem, since code.haskell.org was moved. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Cairo and Haskell
Hello Paulo, << I guess that would be using Cairo so I can have a 2d canvas to draw in and maybe even preview before exporting to PDF. However, I can't find any documentation on Cairo with Haskell or any code examples related to what I want to do. >> With regard to export to pdf and other formats this might be useful: http://muitovar.com/gtk2hs/app1.html (There's a Spanish translation too.) However, this tutorial is a few years old now, and I don't know if it's still up to date for the later Gtk2Hs versions. Best Regards, Hans van Thiel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] "import" functionality in DSLs
On Sat, Apr 16, 2011 at 08:55 CDT, Felipe Almeida Lessa wrote: > On Sat, Apr 16, 2011 at 10:29 AM, Nikhil A. Patil > wrote: > >> doit :: DSL Term > >> doit = do (+) <- (+) > >> n0 <- n0 > >> k <- k > >> -- begin beautiful DSL code > >> let x = k + n0 > >> return $ x + x > > I guess the core problem is that on each time you say '(+) <- (+)', > you may actually get something different depending on what > 'define_function' does. You say yourself that these functions change > a hidden state. So, without any internal changes, I doubt you could > do something better. Thanks very much for your response! You are right, I haven't defined the semantics of this operation in my post. For the example in my post, the define_* functions are idempotent on the hidden state, when used with the same arguments (i.e. the multiple calls are redundant). I explicitly handle this in the implementation of the DSL monad: basically, there is a Set that tracks what functions have been previously defined, and when a conflicting re-definition is found, I throw a run-time error. But: how can I get rid of the boilerplate code, and give the user the appearance that she is "import"-ing identifier bindings from another file? nikhil > > One possible solution may be to have a special case for your Prelude > functions and constants that never change. That is, if currently you > have > > data Term = Term Key ... > type Key = Integer > > and you store other informations about each term on your hidden state, > then you may use > > data Term = Term Key ... > data Key = Prelude Integer | User Integer > > Your define_* functions always return User keys, however now you can > have unsafe versions of them that take a key as argument. Then your > Prelude would be > > > module DSLPrelude where > > > > (+) :: Term -> Term -> Term > > n0 :: Term > > k :: Term > > (+) = unsafe_define_function t1 "+" 2 > > n0 = unsafe_define_constant t2 "0" > > k = unsafe_define_constant t3 "k" > > > > t1, t2, t3 :: Key > > (t1:t2:t3:_) = map Prelude [1..] > > Of course, this is a lot of handwaving, but you haven't provided any > details about your internal implementation. > > HTH, > > -- > Felipe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] "import" functionality in DSLs
On Sat, Apr 16, 2011 at 10:29 AM, Nikhil A. Patil wrote: >> doit :: DSL Term >> doit = do (+) <- (+) >> n0 <- n0 >> k <- k >> -- begin beautiful DSL code >> let x = k + n0 >> return $ x + x I guess the core problem is that on each time you say '(+) <- (+)', you may actually get something different depending on what 'define_function' does. You say yourself that these functions change a hidden state. So, without any internal changes, I doubt you could do something better. One possible solution may be to have a special case for your Prelude functions and constants that never change. That is, if currently you have data Term = Term Key ... type Key = Integer and you store other informations about each term on your hidden state, then you may use data Term = Term Key ... data Key = Prelude Integer | User Integer Your define_* functions always return User keys, however now you can have unsafe versions of them that take a key as argument. Then your Prelude would be > module DSLPrelude where > > (+) :: Term -> Term -> Term > n0 :: Term > k :: Term > (+) = unsafe_define_function t1 "+" 2 > n0 = unsafe_define_constant t2 "0" > k = unsafe_define_constant t3 "k" > > t1, t2, t3 :: Key > (t1:t2:t3:_) = map Prelude [1..] Of course, this is a lot of handwaving, but you haven't provided any details about your internal implementation. HTH, -- Felipe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] "import" functionality in DSLs
Hi, I am planning a simple monadic DSL (frankly, calling it a DSL is a bit of a stretch; it's just a somewhat glorified state monad), and I wish to implement some kind of "import" functionality for it. The DSL code looks something like this: > doit :: DSL Term > doit = do (+) <- define_function "+" 2 > n0 <- define_constant "0" > k <- define_constant "k" > -- begin beautiful DSL code > let x = k + n0 > return $ x + x The code above adds identifiers "+", "0", "k" to the DSL monad and conveniently exposes haskell identifiers (+), n0, k for the user to use in code that follows. (Note that these define_* functions make state updates in the underlying state monad.) Needless to say, most functions like doit have very similar define_* calls in the beginning. Thus, I want to implement some kind of import functionality. Ideally, the code would look like this: > module DSLPrelude where > > prelude :: DSL () > prelude = do (+) <- define_function "+" 2 > n0 <- define_constant "0" > k <- define_constant "k" > return () > module Main where > import DSLPrelude > > doit :: DSL Term > doit = do prelude > -- begin beautiful DSL code > let x = k + n0 > return $ x + x ...but of course that won't work since (+), n0, k are not in scope. I can think of two solutions, both of which I dislike: Solution 1: > module DSLPrelude where > > prelude :: DSL (Term -> Term -> Term, Term, Term) > prelude = do (+) <- define_function "+" 2 > n0 <- define_constant "0" > k <- define_constant "k" > return ((+), n0, k) > module Main where > import DSLPrelude > > doit :: DSL Term > doit = do ((+), k, n0) <- prelude > -- begin beautiful DSL code > let x = k + n0 > return $ x + x This is quite unsafe: I have mistakenly swapped k and n0 in doit, without failing typecheck. Solution 2: > module DSLPrelude where > > (+) :: DSL (Term -> Term -> Term) > n0 :: DSL Term > k :: DSL Term > (+) = define_function "+" 2 > n0 = define_constant "0" > k = define_constant "k" > module Main where > import DSLPrelude > > doit :: DSL Term > doit = do (+) <- (+) > n0 <- n0 > k <- k > -- begin beautiful DSL code > let x = k + n0 > return $ x + x ...which works, but still has quite a bit of boilerplate crap. I feel this would be a common problem with a lot of DSLs, so I am curious to know how others solve it. Any pointers and suggestions are most welcome and greatly appreciated. Thanks! nikhil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] 64 bit generic link warning on every compile
"The -read_only_relocs flag is no longer used on OS X 64, which eliminates some warnings." http://www.haskell.org/ghc/docs/7.0.3/html/users_guide/release-7-0-3.html HTH, Ozgur On 16 April 2011 03:47, Andrew Pennebaker wrote: > GHC 7 compiles fine, but there's an additional warning during linking. > > $ system_profiler SPSoftwareDataType | grep "System Version" > System Version: Mac OS X 10.6.7 (10J869) > $ ghc --version > The Glorious Glasgow Haskell Compilation System, version 7.0.2 > $ cat hello.hs > #!/usr/bin/env runhaskell > > module Main where > > main :: IO () > main = putStrLn "Hello World" > $ ghc --make hello.hs > [1 of 1] Compiling Main ( hello.hs, hello.o ) > Linking hello ... > ld: warning: -read_only_relocs cannot be used with x86_64 > $ ./hello > Hello World > > Cheers, > > Andrew Pennebaker > www.yellosoft.us > > ___ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > > -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
