Re: [Haskell-cafe] Mixing Unboxed Mutable Vectors and Parsers
Hi Myles It seems odd to mix parsing (consuming input) with mutation. What problem are you trying to solve and are you sure you can't get better phase separation than this paragraph suggests? My first idea was to simply parse all the deltas, and later apply them to the input list. However, I can't do that because the value of the deltas depend on the value they're modifying. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Too much inlining on text package
On Apr 8, 2012 8:47 AM, Bryan Oapos;Sullivan b...@serpentine.com wrote: On Sun, Mar 18, 2012 at 12:02 AM, Michael Snoyman mich...@snoyman.com wrote: OK, issue created: https://github.com/bos/text/issues/19 I fixed the too-much-inlining bug tonight. As a bonus, Text literals are now decoded straight from GHC's packed encoding, without an intermediate step through String. Generated code now looks like this at -O and above: $ ghc -O -ddump-simpl -c CS.hs CS.foo :: Data.Text.Internal.Text [GblId, ...] CS.foo = Data.Text.unpackCString# x\NULy This looks great Bryan, thank you! Michael ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Too much inlining on text package
On Sun, Apr 8, 2012 at 2:47 AM, Bryan O'Sullivan b...@serpentine.com wrote: I fixed the too-much-inlining bug tonight. As a bonus, Text literals are now decoded straight from GHC's packed encoding, without an intermediate step through String. Generated code now looks like this at -O and above: $ ghc -O -ddump-simpl -c CS.hs CS.foo :: Data.Text.Internal.Text [GblId, ...] CS.foo = Data.Text.unpackCString# x\NULy Very nice! =) Cheers, -- Felipe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Mixing Unboxed Mutable Vectors and Parsers
It's a JPEG parser. Progressive JPEG is set up where there's a vector Word8s, and some of the entries in the vector may be 0. The JPEG has a stream of bits, and the decoder is supposed to shift in one bit to each successive element in the vector, skipping over 0s, and stop when it reaches some specified number of 0s. So if your partially decoded vector is 2, 8, 0, 12, 0, 10, 6, 0, 2, 10 and the jpeg has this bit stream 1, 1, 0, 1, 0, 0, 1, 0, ... and the jpeg says shift in until the 3rd zero is found that would result in the partially decoded vector being 3, 9, 0, 12, 0, 11, 6, 0, 2, 10 with the leftover part of the stream being 0, 1, 0, ... The JPEG parser has to keep track of where it is in the partially decoded vector to know how many bits to shift in, and where they belong, so the next iteration is aligned to the right place. It would be possible to keep track of this stuff throughout the parsing, and have the result of the parse be a second delta framebuffer and apply it to the original after each scan is parsed, but that's fairly ugly and I'd like to avoid doing that. If that's what I have to do, though, I guess I have to do it. Isn't there a better way? --Myles On Sat, Apr 7, 2012 at 11:56 PM, Stephen Tetley stephen.tet...@gmail.com wrote: Hi Myles It seems odd to mix parsing (consuming input) with mutation. What problem are you trying to solve and are you sure you can't get better phase separation than this paragraph suggests? My first idea was to simply parse all the deltas, and later apply them to the input list. However, I can't do that because the value of the deltas depend on the value they're modifying. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Mixing Unboxed Mutable Vectors and Parsers
On 8 April 2012 19:17, Myles C. Maxfield myles.maxfi...@gmail.com wrote: It's a JPEG parser. Ahem, I'm a bit of of my depth then, but one thing you should consider is that writing your own parser monad is trivial, especially for well defined binary formats. Well defined binary formats should be deterministic and don't need backtracking, hence you won't need to worry about defining Alternative / MonadPlus instances which is where the complication lies. As you should be able to live without backtracking for JPEG it shouldn't be hard to make the parser efficient if you stick closely to the API of the Vector or Array library you are using - e.g. you might want to move a cursor forward through the Array rather than unconsing [*] at the head which would create work for the garbage collector. This should still be amenable to streaming - you just work at a larger chunk size. Presumably you've seen Jeroen Fokker's paper on JPEG decoding with Gofer? (Gofer is ~= Haskell). [*] Parsec etc. work by unconsing the head of the input stream. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] building ghc on arch linux ARM?
Hi Cafe, I hope this is the right place to ask this kind of stuff. I would like to try ghc on a panda board (armv7l) with arch linux. There is apparently no pre-built package, so I was trying the instructions to build, from here: http://hackage.haskell.org/trac/ghc/wiki/Building/Porting. However, I still seem to need a ghc and ghc-pkg installed: I am getting this error message: checking for tar... /bin/tar checking for gpatch... no checking for patch... /usr/bin/patch checking for dtrace... no checking for HsColour... no checking for xmllint... no configure: WARNING: cannot find xmllint in your PATH, you will not be able to validate your documentation checking for xsltproc... no configure: WARNING: cannot find xsltproc in your PATH, you will not be able to build the HTML documentation checking for dblatex... no configure: WARNING: cannot find dblatex in your PATH, you will not be able to build the PDF and PS documentation checking for ghc-pkg matching ... configure: error: Cannot find matching ghc-pkg - Does anyone know if it is possible to build ghc without ghc on this platform? I was using the tarball sources for ghc 7.4.1. Thanks, Christian ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] building ghc on arch linux ARM?
No, it is not possible to build GHC without GHC. Building GHC on ARM is going to be extremely tricky (I'm not sure anyone has ever done it). What you should be able to do easily with the next release is cross-compile to ARM through the LLVM backend. Francesco. On 08/04/12 23:28, . wrote: Hi Cafe, I hope this is the right place to ask this kind of stuff. I would like to try ghc on a panda board (armv7l) with arch linux. There is apparently no pre-built package, so I was trying the instructions to build, from here: http://hackage.haskell.org/trac/ghc/wiki/Building/Porting. However, I still seem to need a ghc and ghc-pkg installed: I am getting this error message: checking for tar... /bin/tar checking for gpatch... no checking for patch... /usr/bin/patch checking for dtrace... no checking for HsColour... no checking for xmllint... no configure: WARNING: cannot find xmllint in your PATH, you will not be able to validate your documentation checking for xsltproc... no configure: WARNING: cannot find xsltproc in your PATH, you will not be able to build the HTML documentation checking for dblatex... no configure: WARNING: cannot find dblatex in your PATH, you will not be able to build the PDF and PS documentation checking for ghc-pkg matching ... configure: error: Cannot find matching ghc-pkg - Does anyone know if it is possible to build ghc without ghc on this platform? I was using the tarball sources for ghc 7.4.1. Thanks, Christian ___ 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] building ghc on arch linux ARM?
On Sun, Apr 8, 2012 at 4:03 PM, Francesco Mazzoli f...@mazzo.li wrote: No, it is not possible to build GHC without GHC. Building GHC on ARM is going to be extremely tricky (I'm not sure anyone has ever done it). I used to use an unregistered build of GHC built by someone in the Debian community - it worked well enough. Cheers, Thomas What you should be able to do easily with the next release is cross-compile to ARM through the LLVM backend. Francesco. On 08/04/12 23:28, . wrote: Hi Cafe, I hope this is the right place to ask this kind of stuff. I would like to try ghc on a panda board (armv7l) with arch linux. There is apparently no pre-built package, so I was trying the instructions to build, from here: http://hackage.haskell.org/trac/ghc/wiki/Building/Porting. However, I still seem to need a ghc and ghc-pkg installed: I am getting this error message: checking for tar... /bin/tar checking for gpatch... no checking for patch... /usr/bin/patch checking for dtrace... no checking for HsColour... no checking for xmllint... no configure: WARNING: cannot find xmllint in your PATH, you will not be able to validate your documentation checking for xsltproc... no configure: WARNING: cannot find xsltproc in your PATH, you will not be able to build the HTML documentation checking for dblatex... no configure: WARNING: cannot find dblatex in your PATH, you will not be able to build the PDF and PS documentation checking for ghc-pkg matching ... configure: error: Cannot find matching ghc-pkg - Does anyone know if it is possible to build ghc without ghc on this platform? I was using the tarball sources for ghc 7.4.1. Thanks, Christian ___ 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] building ghc on arch linux ARM?
Thomas DuBuisson wrote: On Sun, Apr 8, 2012 at 4:03 PM, Francesco Mazzoli f...@mazzo.li wrote: No, it is not possible to build GHC without GHC. Building GHC on ARM is going to be extremely tricky (I'm not sure anyone has ever done it). I used to use an unregistered build of GHC built by someone in the Debian community - it worked well enough. It ships with Debian, along with the full Haskell Platform built for ARM and lots of other libraries. Other than speed, it's fine. -- see shy jo signature.asc Description: Digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Category Theory Questions
Hello, I have a question not that directly related to Haskell, but I still think this is a good place to ask it. I am currently studying category theory by the book Joy of Cats. Are there any people whom I could ask some questions related to category theory from time to time? Or could I just post my questions here directly? The reason I'm asking is that I seen very nice discussions related to category theory on this list. I hope to be able to deal with most of the stuff myself, but having someone to discuss the matters with is always nice :-) Sergiu [0] katmat.math.uni-bremen.de/acc/acc.pdf ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Category Theory Questions
I am not sure if this is a good forum to ask Category theory related questions as such. Some better options may be math.stackexchange.com or mathoverflow.net. Many category theory ideas are implemented in Haskell. So some discussion may have happened over here but surely its not a forum on category theory (IMHO) . Just a thought. -- Dilawar Singh On Mon, Apr 9, 2012 at 10:07 AM, Sergiu Ivanov unlimitedscol...@gmail.comwrote: Hello, I have a question not that directly related to Haskell, but I still think this is a good place to ask it. I am currently studying category theory by the book Joy of Cats. Are there any people whom I could ask some questions related to category theory from time to time? Or could I just post my questions here directly? The reason I'm asking is that I seen very nice discussions related to category theory on this list. I hope to be able to deal with most of the stuff myself, but having someone to discuss the matters with is always nice :-) Sergiu [0] katmat.math.uni-bremen.de/acc/acc.pdf ___ 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] Category Theory Questions
I doubt anyone will mind too much, but you probably want to stick to the category theory that is obviously applicable to Haskell (and ideally talk/ask about how it applies). Questions about initial algebras and Lambek's lemma will probably get decent responses, whereas globe categories and anafunctors, for example, might not. If it's just straight-up category theory for its own sake, you might have better luck on math-specific forums (stack exchange, for example), though. Dan On Mon, Apr 9, 2012 at 12:37 AM, Sergiu Ivanov unlimitedscol...@gmail.comwrote: Hello, I have a question not that directly related to Haskell, but I still think this is a good place to ask it. I am currently studying category theory by the book Joy of Cats. Are there any people whom I could ask some questions related to category theory from time to time? Or could I just post my questions here directly? The reason I'm asking is that I seen very nice discussions related to category theory on this list. I hope to be able to deal with most of the stuff myself, but having someone to discuss the matters with is always nice :-) Sergiu [0] katmat.math.uni-bremen.de/acc/acc.pdf ___ 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
