Re: [Haskell-cafe] A weird bug of regex-pcre
On Tue, Dec 18, 2012 at 02:28:26PM +0800, Magicloud Magiclouds wrote: Attachment is the test text file. And I tested my regexp as this: Prelude :m + Text.Regex.PCRE Prelude Text.Regex.PCRE z - readFile test.html Prelude Text.Regex.PCRE let (b, m ,a, ss) = z =~ a href=\(.*?)\.*?img class=\article-image\ :: (String, String, String, [String]) Prelude Text.Regex.PCRE b ... n of the Triumvirate/td\r\ntd class=\small\David Rapoza/td\r\n td class=\small\\r\n iReturn to Ravnica/i\r\n/td\r\n td class=\small\10/31/2012/td\r\n /trtr\r\n td class=\small\ Prelude Text.Regex.PCRE m a href=\/magic/magazine/article.aspx?x=mtg/daily/activity/1088\img class=\article-image\ From the value of b and m, it was weird that the matching was moved forward by 1 char ( the ss (sub matching) was even worse, 2 chars ). Rematch to a and so on gave correct results. It was only the first matching that was broken. Tested with regex-posix (with modified regexp), everything is OK. I have a similar issue with non-ascii strings. It seems that the internal representation used by Haskell and pcre are different and one of them is counting bytes and the other is counting code points. So they diverge when a multi-byte representation (like utf8) is used. It has been reported previously. See these threads: http://www.haskell.org/pipermail/haskell-cafe/2012-August/thread.html#102959 http://www.haskell.org/pipermail/haskell-cafe/2012-August/thread.html#103029 I am still waiting for a new release of regex-pcre that fixes this issue. Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] regex-pcre and ghc-7.4.2 is not working with UTF-8
Hello. I think I have an explanation for the problem with regex-pcre, ghc-7.4.2 and UTF Strings. The Text.Regex.PCRE.String module uses the withCString and withCStringLen from the module Foreign.C.String to pass a Haskell string to the C library pcre functions that compile regular expressions, and execute regular expressions to match some text. Recent versions of ghc have withCString and withCStringLen definitions that uses the current system locale to define the marshalling of a Haskell string into a NUL terminated C string using temporary storage. With a UTF-8 locale the length of the C string will be greater than the length of the corresponding Haskell string in the presence with characters outside of the ASCII range. Therefore positions of corresponding characters in both strings do not match. In order to compute matching positions, regex-pcre functions use C strings. But to compute matching strings they use those positions with Haskell strings. That gives the mismatch shown earlier and repeated here with the attached program run on a system with a UTF-8 locale: $ LANG=en_US.UTF-8 ./test1 getForeignEncoding: UTF-8 regex: país:(.*):(.*) text : país:Brasília:Brasil String matchOnce : Just (array (0,2) [(0,(0,22)),(1,(6,9)),(2,(16,6))]) String match : [[pa\237s:Bras\237lia:Brasil,ras\237lia:B,asil]] $ LANG=en_US.ISO-8859-1 ./test1 getForeignEncoding: ISO-8859-1 regex: pa�s:(.*):(.*) text : pa�s:Bras�lia:Brasil String matchOnce : Just (array (0,2) [(0,(0,20)),(1,(5,8)),(2,(14,6))]) String match : [[pa\237s:Bras\237lia:Brasil,Bras\237lia,Brasil]] I see two ways of fixing this bug: 1. make the matching functions compute the text using the C string and the positions calculated by the C function, and convert the text back to a Haskell string. 2. map the positions in the C string (if possible) to the corresponding positions in the Haskell string; this way the current definitions of the matching functions returning text will just work. I hope this would help fixing the issue. Regards, Romildo module Main where import GHC.IO.Encoding (getForeignEncoding) import Data.Bits (Bits((..))) import Text.Regex.PCRE testpcre re text = do putStrLn (regex: ++ re) putStrLn (text : ++ text) putStrLn (String matchOnce : ++ show mo) putStrLn (String match : ++ show m) where c = defaultCompOpt .. compUTF8 e = defaultExecOpt regex = makeRegexOpts c e re :: Regex mo = matchOnce regex text m = match regex text :: [[String]] main = do enc - getForeignEncoding putStrLn (getForeignEncoding: ++ show enc) putStrLn testpcre país:(.*):(.*) país:Brasília:Brasil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] regex-pcre and ghc-7.4.2 is not working with UTF-8
On Thu, Aug 23, 2012 at 08:59:52AM -0300, José Romildo Malaquias wrote: Hello. I think I have an explanation for the problem with regex-pcre, ghc-7.4.2 and UTF Strings. The Text.Regex.PCRE.String module uses the withCString and withCStringLen from the module Foreign.C.String to pass a Haskell string to the C library pcre functions that compile regular expressions, and execute regular expressions to match some text. Recent versions of ghc have withCString and withCStringLen definitions that uses the current system locale to define the marshalling of a Haskell string into a NUL terminated C string using temporary storage. With a UTF-8 locale the length of the C string will be greater than the length of the corresponding Haskell string in the presence with characters outside of the ASCII range. Therefore positions of corresponding characters in both strings do not match. In order to compute matching positions, regex-pcre functions use C strings. But to compute matching strings they use those positions with Haskell strings. That gives the mismatch shown earlier and repeated here with the attached program run on a system with a UTF-8 locale: $ LANG=en_US.UTF-8 ./test1 getForeignEncoding: UTF-8 regex: país:(.*):(.*) text : país:Brasília:Brasil String matchOnce : Just (array (0,2) [(0,(0,22)),(1,(6,9)),(2,(16,6))]) String match : [[pa\237s:Bras\237lia:Brasil,ras\237lia:B,asil]] $ LANG=en_US.ISO-8859-1 ./test1 getForeignEncoding: ISO-8859-1 regex: pa�s:(.*):(.*) text : pa�s:Bras�lia:Brasil String matchOnce : Just (array (0,2) [(0,(0,20)),(1,(5,8)),(2,(14,6))]) String match : [[pa\237s:Bras\237lia:Brasil,Bras\237lia,Brasil]] I see two ways of fixing this bug: 1. make the matching functions compute the text using the C string and the positions calculated by the C function, and convert the text back to a Haskell string. 2. map the positions in the C string (if possible) to the corresponding positions in the Haskell string; this way the current definitions of the matching functions returning text will just work. I hope this would help fixing the issue. I have a fix for this bug and it would be nice if others take a look at it and see if it is ok. It is based on the second way presented above. Romildo diff -ur regex-pcre-0.94.4.orig/Text/Regex/PCRE/String.hs regex-pcre-0.94.4/Text/Regex/PCRE/String.hs --- regex-pcre-0.94.4.orig/Text/Regex/PCRE/String.hs2012-05-30 18:44:14.0 -0300 +++ regex-pcre-0.94.4/Text/Regex/PCRE/String.hs 2012-08-23 17:22:14.114641657 -0300 @@ -46,11 +46,16 @@ ) where import Text.Regex.PCRE.Wrap -- all -import Foreign.C.String(withCStringLen,withCString) -import Data.Array(Array,listArray) +import Foreign.C.String(CStringLen,withCStringLen,withCString) +import Foreign.Storable(peekByteOff) +import Data.Word(Word8) +import Data.Array.IO(IOUArray,newArray,readArray,writeArray) +import Data.Array(Array,listArray,bounds,elems) import System.IO.Unsafe(unsafePerformIO) -import Text.Regex.Base.RegexLike(RegexMaker(..),RegexLike(..),RegexContext(..),MatchLength,MatchOffset) +import Text.Regex.Base.RegexLike(RegexMaker(..),RegexLike(..),RegexContext(..),MatchLength,MatchOffset,MatchArray) import Text.Regex.Base.Impl(polymatch,polymatchM) +import GHC.IO.Encoding(getForeignEncoding,textEncodingName) +import Control.Monad(forM) instance RegexContext Regex String String where match = polymatch @@ -72,7 +77,7 @@ matchOnce regex str = unsafePerformIO $ execute regex str = unwrap matchAll regex str = unsafePerformIO $ -withCStringLen str (wrapMatchAll regex) = unwrap +withCStringLen str (wrapMatchAllFixPos regex) = unwrap matchCount regex str = unsafePerformIO $ withCStringLen str (wrapCount regex) = unwrap @@ -91,7 +96,7 @@ -- string, or: -- 'Just' an array of (offset,length) pairs where index 0 is whole match, and the rest are the captured subexpressions. execute regex str = do - maybeStartEnd - withCStringLen str (wrapMatch 0 regex) + maybeStartEnd - withCStringLen str (wrapMatchFixPos 0 regex) case maybeStartEnd of Right Nothing - return (Right Nothing) -- Right (Just []) - fail got [] back! -- should never happen @@ -115,9 +120,94 @@ ,getSub matchedStartStop ,drop stop str ,map getSub subStartStop) - maybeStartEnd - withCStringLen str (wrapMatch 0 regex) + maybeStartEnd - withCStringLen str (wrapMatchFixPos 0 regex) case maybeStartEnd of Right Nothing - return (Right Nothing) -- Right (Just []) - fail got [] back! -- should never happen Right (Just parts) - return . Right . Just . matchedParts $ parts Left err - return (Left err) + + + +-- | wrapMatchFixPos calls wrapMatch and fixes the string offsets +-- in the result so that they are valid in the original Haskell string
Re: [Haskell-cafe] regex-pcre is not working with UTF-8
On Tue, Aug 21, 2012 at 05:50:44PM -0300, José Romildo Malaquias wrote:
On Tue, Aug 21, 2012 at 04:05:28PM +0100, Chris Kuklewicz wrote:
I do not have time to test this myself right now. But I will unravel my
code a
bit for you.
By November 2011 it worked without problems in my application. Now that
I have resumed developping the application, I have been faced with this
behaviour. As it used to work before, I believe it is a bug in
regex-pcre or libpcre.
I believe it may be problem in String - ByteString conversion. The base
library may have changed and your LOCALE information may be different or
may be
being used differently by base.
The (temporary) workaround I found is to convert the strings to
byte-strings before matching, and then convert the results back to
strings. With byte-strings it works well.
That is an excellent sign that it is your LOCALE settings being picked up by
GHC's base package, see explanation below.
[...]
I have written an application to test those things. There are 2 source
files: test.hs and seestr.c, which are attached.
The test does the following:
1. shows the getForeignEncoding
2. uses a C function to show the characters from a String (using
withCString) and from a ByteString (using useAsCString)
3. matches a PCRE regular expression using String and ByteString
The test is run twice, with different LANG settings, and its output
follows.
[...]
As can be seen, regular expression matching does not work with
en_US.UTF-8. But it works with en_US.ISO-8859-1.
The test shows that withCString is working as expected too. This
may suggest the problem is really with regex-pcre.
The previous tests were run on an gentoo linux with ghc-7.4.1.
I have also run the tests on Fedora 17 with ghc-7.0.4, which does not
have the bug. The sources are attached. The tests output follows:
$ LANG=en_US.ISO-8859-1 ./test
testing with String
code: 70, char: p
code: 61, char: a
code: ffed, char:
code: 73, char: s
result: 4
testing with ByteString
code: 70, char: p
code: 61, char: a
code: ffed, char:
code: 73, char: s
result: 4
regex: pa�s:(.*)
text : pa�s:Brasil
String match : [[pa\237s:Brasil,Brasil]]
ByteString match : [[pa\237s:Brasil,Brasil]]
$ LANG=en_US.UTF-8 ./test
testing with String
code: 70, char: p
code: 61, char: a
code: ffed, char:
code: 73, char: s
result: 4
testing with ByteString
code: 70, char: p
code: 61, char: a
code: ffed, char:
code: 73, char: s
result: 4
regex: país:(.*)
text : país:Brasil
String match : [[pa\237s:Brasil,Brasil]]
ByteString match : [[pa\237s:Brasil,Brasil]]
Clearly witchCString has changed from ghc-7.0.4 to ghc-7.4.1. It seems
that With ghc-7.0.4 withCString does not obey the UTF-8 locale and
generates a latin1 C string.
Regards,
Romildo
module Main where
--import GHC.IO.Encoding (getForeignEncoding)
import Data.Bits (Bits((..)))
import Foreign.C.Types (CChar, CInt(..))
import Foreign.C.String
import Foreign.Ptr
import Text.Regex.PCRE
import qualified Data.ByteString.Char8 as B
foreign import ccall seestr
seestr :: Ptr CChar - IO CInt
seeStr :: String - IO Int
seeStr s = do ci - withCString s seestr
return $ fromInteger (toInteger ci)
seeChar8 :: B.ByteString - IO Int
seeChar8 s = do ci - B.useAsCString s seestr
return $ fromInteger (toInteger ci)
test :: String - IO ()
test s = do putStrLn testing with String
x - seeStr s
putStrLn (result: ++ show x)
putStrLn
putStrLn testing with ByteString
x - seeChar8 (B.pack s)
putStrLn (result: ++ show x)
testpcre re text = do putStrLn (regex: ++ re)
putStrLn (text : ++ text)
putStrLn (String match : ++ show m1)
putStrLn (ByteString match : ++ show m2)
where
c = defaultCompOpt .. compUTF8
e = defaultExecOpt
m1 = match (makeRegexOpts c e re :: Regex) text :: [[String]]
m2 = match (makeRegexOpts c e (B.pack re) :: Regex) (B.pack text) :: [[B.ByteString]]
main = do --enc - getForeignEncoding
--putStrLn (getForeignEncoding: ++ show enc)
--putStrLn
test país
putStrLn
testpcre país:(.*) país:Brasil
#include stdio.h
int seestr(const char *str)
{
int counter = 0;
while (*str)
{
printf(code: %8x, char: %c\n, *str, *str);
counter ++;
str ++;
}
return counter;
}
___
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Re: [Haskell-cafe] regex-pcre is not working with UTF-8
On Tue, Aug 21, 2012 at 10:25:53PM +0300, Konstantin Litvinenko wrote: On 08/18/2012 06:16 PM, José Romildo Malaquias wrote: Hello. It seems that the regex-pcre has a bug dealing with utf-8: I hope this bug can be fixed soon. Is there a bug tracker to report the bug? If so, what is it? You need something like that let pat = makeRegexOpts (compUTF8 .|. defaultCompOpt) defaultExecOpt (@'(.+?)'@ :: B.ByteString) and than pat will match correctly. The bug is related to String (not ByteString) in a UTF-8 locale. Until it is fixed, I am using the workaround of converting the regular expression and the text to ByteString, doing the matching, and then converting the results back to String. Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Regex string replacement
Hello. I am looking for a substring replacement based on Perl like regular expressions that would let me use part of the original string in the replacement string. Something like: reReplace name is (.*)\\. hi \1! my name is john. which would result in hy john! Any help? Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Regex string replacement
On Sat, Aug 18, 2012 at 09:39:01AM -0300, Marco Túlio Pimenta Gontijo wrote: Hi Romildo. On Sat, Aug 18, 2012 at 9:18 AM, José Romildo Malaquias j.romi...@gmail.com wrote: (...) I am looking for a substring replacement based on Perl like regular expressions that would let me use part of the original string in the replacement string. Something like: reReplace name is (.*)\\. hi \1! my name is john. which would result in hy john! It's not exactly what you're looking for, but I'd simply do something like this, using Text.Regex.TDFA or any other: let [[_, name]] = my name is john. =~ name is (.*)\\. in hi ++ name ++ ! Thanks for the tip. It was useful to solve my original problem. Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] regex-pcre is not working with UTF-8
Hello. It seems that the regex-pcre has a bug dealing with utf-8: Prelude :m + Text.Regex.PCRE Prelude Text.Regex.PCRE país:Brasil =~ país:(.*) :: (String,String,String,[String]) (,pa\237s:Brasil,,[rasil]) Notice the missing 'B' in the result of the regex matching. With regex-posix this does not happen: Prelude :m + Text.Regex.Posix Prelude Text.Regex.Posix país:Brasil =~ país:(.*) ::(String,String,String,[String]) (,pa\237s:Brasil,,[Brasil]) I hope this bug can be fixed soon. Is there a bug tracker to report the bug? If so, what is it? Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Annotaing abstract syntax trees
Hello.
I am reading Martijn's MSc Thesis Generic Selections of
Subexpressions, where one can found some discussions about annotating
abstract syntax trees (AST).
In order to follow the discussion I wrote the attached Haskell program,
which is an interpreter for an simple typed expression language. The
Annotations package is used.
The expression pattern is represented by a single recursive data
type. Annotations are used for positions in the input source, and also
for the type of expressions and subexpressions.
I would like somebody to review the code and comment on it, as I am not
sure I am using the concepts right.
Also I would like the type checker to produce an expression annotated
with both positions and calculated types. Currently it discards the
position annotations. Any sugestions on how to modify it is welcome.
Next step is adding a new form of expression to introduce local variable
bindings.
After that I want to start working with ASTs represented by mutually
recursive data types. Then I will need multirec...
Romildo
{-# LANGUAGE FlexibleContexts #-}
module Main where
import Control.Applicative (Applicative(pure,(*)),($),($),(*))
import Data.Traversable (Traversable(traverse))
import Data.Foldable (Foldable(foldr))
import Text.Parsec hiding (chainl1)
import Data.Char (isDigit,isAlpha,isAlphaNum)
import Data.Tree (Tree(Node),drawTree)
import Annotations.F.Fixpoints
import Annotations.F.Annotated
import Annotations.Except
-- the goal is to implement an interpreter for a simple language of
-- typed expressions using annotations on recursive data types
-- type of expressions
data ExprType
= NUMERIC
| LOGIC
deriving (Show)
-- value of an expression
data ExprValue
= Numeric Double
| Logic Bool
deriving (Show)
-- identifiers are strings
type Id = String
-- binary operators used in expressions
data Op
= Add | Sub | Mul | Div -- arithmetic
| Eq | Ne | Gt | Ge | Lt | Le -- relational
| And | Or -- logical
deriving (Show)
-- pattern of an expression
data ExprF r
= Num Double -- numeric literal
| Log Bool -- logical literal
| Var Id -- variable
| Bin Op r r -- binary operation
deriving (Show)
-- mapping a function over an expression pattern
instance Functor ExprF where
fmap _ (Num n) = Num n
fmap _ (Log b) = Log b
fmap _ (Var v) = Var v
fmap f (Bin op x y) = Bin op (f x) (f y)
-- traversing an expression pattern
instance Traversable ExprF where
traverse _ (Num n) = pure (Num n)
traverse _ (Log b) = pure (Log b)
traverse _ (Var v) = pure (Var v)
traverse f (Bin op x y) = Bin op $ f x * f y
-- folding an expression pattern
instance Foldable ExprF where
foldr _ z (Num _) = z
foldr _ z (Log _) = z
foldr _ z (Var _) = z
foldr f z (Bin op l r) = f l (f r z)
-- bare expressions
newtype Expr
= Expr { runExpr :: Fix ExprF }
deriving (Show)
-- range of source positions: used to delimit where something appeared
-- in a source input
data Range
= Range SourcePos SourcePos
instance Show Range where
show (Range p1 p2)
| n1 == n2 = if null n1
then showLC lc1 ++ - ++ showLC lc2
else showN n1 ++ ++ showLC lc1 ++ - ++ showLC lc2
| otherwise = showN n1 ++ ++ showLC lc1 ++ - ++ showN n2 ++ ++ showLC lc2
where
n1 = sourceName p1
lc1 = (sourceLine p1,sourceColumn p1)
n2 = sourceName p2
lc2 = (sourceLine p2,sourceColumn p2)
showN n = \ ++ n ++ \
showLC (l,c) = show l ++ : ++ show c
-- expressions annoted with positions
newtype PosExpr
= PosExpr { runPosExpr :: Fix (Ann Range ExprF) }
deriving (Show)
-- convert an expression to a rose tree of strings
-- this helps to visualize the expression structure
exprTree :: Algebra ExprF (Tree String)
exprTree (Num n) = Node (Num: ++ show n) []
exprTree (Log b) = Node (Log: ++ show b) []
exprTree (Var v) = Node (Var: ++ v) []
exprTree (Bin op l r) = Node (Bin: ++ show op) [l,r]
-- convert an annotated expression to a tree of strings
-- this helps to visualize the annotated expression structure
annExprTree :: Show a = Algebra (Ann a ExprF) (Tree String)
annExprTree (Ann z expr) =
case expr of
Num n - Node (annot (Num: ++ show n)) []
Log b - Node (annot (Log: ++ show b)) []
Var v - Node (annot (Var: ++ v)) []
Bin op l r - Node (annot (Bin: ++ show op)) [l,r]
where
annot x = x ++ ++ show z
-- a memory is just an association list between
-- variable names and values
type Memory = [(Id,ExprValue)]
-- an algebra to find the value of an expression annotated with
-- positions, given a memory
exprEval :: Memory - ErrorAlgebra ExprF String ExprValue
exprEval _ (Num n) = Right (Numeric n)
exprEval _ (Log b) = Right (Logic b)
exprEval m (Var v) = case lookup v m of
Just x - Right x;
Nothing - Left (undefined
[Haskell-cafe] Parameters and patterns
Hello. When studing programming languages I have learned that parameter is a variable (name) that appears in a function definition and denotes the value to which the function is applied when the function is called. Argument is the value to which the function is applied. The parameter allows the manipulation of the argument in the body of the funtion definition in order to produce the result. Now I am not sure how to apply these concepts to Haskell, as Haskell uses pattern matching to deal with argument passing to functions. For instance, in the definition f x = 2 * x + 1 x is a parameter, and in the application f 34 34 is an argument. But in the definition g (_:xs) = xs what is the parameter of the function g? Is it the pattern (_:xs)? If so then a parameter is not necessarily a variable anymore, and that seems very strange. And what is xs? Is it a parameter, although it does not denote the value to which the function is aplied, but just part of it? I am writing some slides to use in my functional programming classes, but I am not sure how to deal with these terms. Any comments? Romildo -- DECOM - ICEB - UFOP ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ghc-mtl and ghc-7.2.1
Hello. In order to compile ghc-mtl-1.0.1.0 (the latest released version) with ghc-7.2.1, I would apply the attached patch, which removes any references to WarnLogMonad. ghc-7.2.1 does not have the monad WarnLogMonad anymore. As I do not know the details of the GHC api, I am not sure if this is enough to use ghc-mtl with ghc-7.2.1. I want ghc-mtl in order do build lambdabot. Any thoughts? Romildo diff -ur ghc-mtl-1.0.1.0.orig/Control/Monad/Ghc.hs ghc-mtl-1.0.1.0/Control/Monad/Ghc.hs --- ghc-mtl-1.0.1.0.orig/Control/Monad/Ghc.hs 2011-09-07 07:38:20.297885351 -0300 +++ ghc-mtl-1.0.1.0/Control/Monad/Ghc.hs2011-09-07 08:31:44.132815320 -0300 @@ -12,13 +12,15 @@ import Control.Monad.CatchIO import qualified GHC ( runGhc, runGhcT ) -import qualified HscTypes as GHC +-- import qualified HscTypes as GHC +import qualified GhcMonad as GHC import qualified MonadUtils as GHC import qualified Exception as GHC newtype Ghc a = Ghc (GHC.Ghc a) deriving (Functor, Monad, - GHC.WarnLogMonad, GHC.ExceptionMonad, GHC.MonadIO, GHC.GhcMonad) + -- GHC.WarnLogMonad, + GHC.ExceptionMonad, GHC.MonadIO, GHC.GhcMonad) instance MTL.MonadIO Ghc where liftIO = GHC.liftIO @@ -56,9 +58,9 @@ gblock = block gunblock = unblock -instance MTL.MonadIO m = GHC.WarnLogMonad (GhcT m) where -setWarnings = GhcT . GHC.setWarnings -getWarnings = GhcT GHC.getWarnings +-- instance MTL.MonadIO m = GHC.WarnLogMonad (GhcT m) where +-- setWarnings = GhcT . GHC.setWarnings +-- getWarnings = GhcT GHC.getWarnings instance (Functor m, MonadCatchIO m) = GHC.GhcMonad (GhcT m) where getSession = GhcT GHC.getSession ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Subtitles for Programming in Haskell videos
Hello. Are there subtitles (in English or Portuguese) for the video lectures[1] given by Erik Meijer using the book Programming in Haskell, by Graham Hutton? [1] http://www.cs.nott.ac.uk/~gmh/book.html Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] error with nanocurses-1.5.2
On Sat, Jul 09, 2011 at 01:59:12PM -0300, José Romildo Malaquias wrote:
Hello.
When trying to install nanocurses-1.5.2 on my Fedora Linux system, I am
getting the following error:
$ cabal install nanocurses
Resolving dependencies...
Configuring nanocurses-1.5.2...
Preprocessing library nanocurses-1.5.2...
In file included from Curses.hsc:42:0:
cbits/utils.h:7:20: fatal error: config.h: No such file or directory
compilation terminated.
compiling dist/build/UI/Nanocurses/Curses_hsc_make.c failed (exit code 1)
command was: /usr/bin/gcc -c dist/build/UI/Nanocurses/Curses_hsc_make.c
-o dist/build/UI/Nanocurses/Curses_hsc_make.o -fno-stack-protector
-fno-stack-protector -D__GLASGOW_HASKELL__=700 -Dlinux_BUILD_OS
-Dlinux_HOST_OS -Dx86_64_BUILD_ARCH -Dx86_64_HOST_ARCH -Icbits
-I/usr/lib64/ghc-7.0.2/unix-2.4.2.0/include
-I/usr/lib64/ghc-7.0.2/bytestring-0.9.1.10/include
-I/usr/lib64/ghc-7.0.2/base-4.3.1.0/include
-I/usr/lib64/ghc-7.0.2/include -I/usr/lib64/ghc-7.0.2/include/
cabal: Error: some packages failed to install:
nanocurses-1.5.2 failed during the building phase. The exception was:
ExitFailure 1
It would be nice to have this buf fixed.
The attached patch fixes the compilation issues. Basically it changes
the build type from simple to configure in the cabal file, and it
renames the function getline in cbits/utils.{h,c} to mygetline.
If appropriate, please release a new version with the fixes.
Romildo
diff -ur nanocurses-1.5.2.orig/cbits/utils.c nanocurses-1.5.2/cbits/utils.c
--- nanocurses-1.5.2.orig/cbits/utils.c 2008-05-18 18:09:23.0 -0300
+++ nanocurses-1.5.2/cbits/utils.c 2011-07-10 11:23:02.082418889 -0300
@@ -38,7 +38,7 @@
}
/* sometimes we write to the wrong spot after a refresh */
-int getline(char *buf, FILE *hdl) {
+int mygetline(char *buf, FILE *hdl) {
char *p;
int c;
@@ -52,7 +52,7 @@
while (c != '\n')
c = getc(hdl);
-return getline(buf,hdl);/* read another line */
+return mygetline(buf,hdl);/* read another line */
/* normal packet */
} else {
@@ -60,7 +60,7 @@
p = fgets(buf+1, BUFLEN-1, hdl); /* read rest of line */
if (p == NULL) {
-// perror(getline failed\n);
+// perror(mygetline failed\n);
return (-1);
}
buf[0] = c; /* drop the '@' */
diff -ur nanocurses-1.5.2.orig/cbits/utils.h nanocurses-1.5.2/cbits/utils.h
--- nanocurses-1.5.2.orig/cbits/utils.h 2008-05-18 18:09:23.0 -0300
+++ nanocurses-1.5.2/cbits/utils.h 2011-07-10 11:22:18.180418821 -0300
@@ -12,5 +12,5 @@
/* packed string IO */
FILE *openfd(int fd);
-int getline(char *buf, FILE *hdl);
+int mygetline(char *buf, FILE *hdl);
void forcenext(void);
diff -ur nanocurses-1.5.2.orig/nanocurses.cabal
nanocurses-1.5.2/nanocurses.cabal
--- nanocurses-1.5.2.orig/nanocurses.cabal 2008-05-18 18:09:23.0
-0300
+++ nanocurses-1.5.2/nanocurses.cabal 2011-07-10 11:21:43.256418788 -0300
@@ -21,7 +21,7 @@
(It does not differ significantly from Hmp3's Curses
binding, as the Curses.hsc
in Nanocurses is essentially extracted from Hmp3.)
-build-type: Simple
+build-type: Configure
build-depends: base3, unix, bytestring
tested-with:GHC==6.8.2
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Re: [Haskell-cafe] unbuffered raw keyboard input on Windows
On Wed, Jul 06, 2011 at 02:48:47PM -0700, David Barbour wrote: You could try the SDL package to support user input. Unfortunatly it does not run on a terminal. 2011/7/6 José Romildo Malaquias j.romi...@gmail.com Hello. I want to write a Haskell console application (a game) in ghc where the user will interact using the keyboard. I need to read the keys as soon as they are typed and without echoing to the console. Although Haskell provides this capability in the standard libraries (using hSetEcho and hSetBuffering from System.IO), it does not work on Windows due to a bug (http://hackage.haskell.org/trac/ghc/ticket/2189). I have tried installing packages like vty, hscurses, and ncurses, but they did not install on Windows. Which workarounds are available for that? Romildo ___ 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] unbuffered raw keyboard input on Windows
On Wed, Jul 06, 2011 at 06:46:32PM -0300, José Romildo Malaquias wrote: Hello. I want to write a Haskell console application (a game) in ghc where the user will interact using the keyboard. I need to read the keys as soon as they are typed and without echoing to the console. Although Haskell provides this capability in the standard libraries (using hSetEcho and hSetBuffering from System.IO), it does not work on Windows due to a bug (http://hackage.haskell.org/trac/ghc/ticket/2189). I have tried installing packages like vty, hscurses, and ncurses, but they did not install on Windows. Considering that there are curses for Windows (pdcurses[1] and the latest ncurses[2]), would it be too difficult to port such libraries to Windows? [1] http://pdcurses.sourceforge.net/ [2] http://www.gnu.org/software/ncurses/ Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] unbuffered raw keyboard input on Windows
Hello. I want to write a Haskell console application (a game) in ghc where the user will interact using the keyboard. I need to read the keys as soon as they are typed and without echoing to the console. Although Haskell provides this capability in the standard libraries (using hSetEcho and hSetBuffering from System.IO), it does not work on Windows due to a bug (http://hackage.haskell.org/trac/ghc/ticket/2189). I have tried installing packages like vty, hscurses, and ncurses, but they did not install on Windows. Which workarounds are available for that? Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] GHC and MinGW
Hello. How do I make ghc use my installation of MinGW on Windows? I have ghc-7.0.1 installed and the latest MinGW packages. I want ghc to automatically find libraries installed by the MinGW installer. Currently I am getting the error with my application: Linking Gui.exe ... C:\Program Files\Haskell\iconv-0.4.1.0\ghc-7.0.1/libHSiconv-0.4.1.0.a(hsiconv.o):hsiconv.c:(.text+0x8): undefined reference to `libiconv_open' where libiconv has been installed with the command mingw-get install mingw32-libiconv and the library is available at c:/devel/MinGW/lib/ Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GHC and MinGW
On Sat, Feb 12, 2011 at 01:12:22PM -0200, José Romildo Malaquias wrote: Hello. How do I make ghc use my installation of MinGW on Windows? I have ghc-7.0.1 installed and the latest MinGW packages. I want ghc to automatically find libraries installed by the MinGW installer. Currently I am getting the error with my application: Linking Gui.exe ... C:\Program Files\Haskell\iconv-0.4.1.0\ghc-7.0.1/libHSiconv-0.4.1.0.a(hsiconv.o):hsiconv.c:(.text+0x8): undefined reference to `libiconv_open' where libiconv has been installed with the command mingw-get install mingw32-libiconv and the library is available at c:/devel/MinGW/lib/ Looking at iconv.cabal from the iconv package, I found this: if os(darwin) || os(freebsd) -- on many systems the iconv api is part of the standard C library -- but on some others we have to link to an external libiconv: extra-libraries: iconv So the problem is that the extra library iconv is not been considered for the windows os. Changing the line above to consider the windows os solves the problem: if os(darwin) || os(freebsd) || os(windows) -- on many systems the iconv api is part of the standard C library -- but on some others we have to link to an external libiconv: extra-libraries: iconv Therefore the mantainer of the iconv package should fix this issue. Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] regex libraries: matching operators (=~) and (=~~) are not methods
On Tue, Nov 30, 2010 at 05:50:02PM -0200, José Romildo Malaquias wrote: Hello. When learning how to use the many regular expression libraries for Haskell, I noticed that the interface API from the regex-base package introduces several high level operations that are abstracted from the implementations (backends). This is done by means of classes. For instance, there are methods for compiling an external representation (like a string or a bytestring) into a regular expression. There are also methods for matching a regular expression and some text (like a string, or a bytestring). But the most high level functions for pattern matching using regular expressions, (=~) and (=~~), are not defined as methods in a class. They are independent functions defined for each backend in the corresponding package. This prevents one from writing a general function using these operators without deliberately choosing a regex backend. Why are those operators not defined as methods, like all other relevant functions? I think I have found the reason for that. Let's consider the operator (=~ ). Its type in the Text.Regex.TDFA is: ( RegexMaker Regex CompOption ExecOption source , RegexContext Regex source1 target ) = source1 - source - target It has two arguments: the text and the regex (in a textual format) used in matching. They may be both of type String, or ByteString, for instance. Therefore there is no way to infer which regex engine to use when the regex text is compiled to an internal format. So the regex engine cannot be deduced automatically from the arguments. Because of that each regex backend has to define his own function, and a class is of no help. Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] regex libraries: matching operators (=~) and (=~~) are not methods
Hello. When learning how to use the many regular expression libraries for Haskell, I noticed that the interface API from the regex-base package introduces several high level operations that are abstracted from the implementations (backends). This is done by means of classes. For instance, there are methods for compiling an external representation (like a string or a bytestring) into a regular expression. There are also methods for matching a regular expression and some text (like a string, or a bytestring). But the most high level functions for pattern matching using regular expressions, (=~) and (=~~), are not defined as methods in a class. They are independent functions defined for each backend in the corresponding package. This prevents one from writing a general function using these operators without deliberately choosing a regex backend. Why are those operators not defined as methods, like all other relevant functions? Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] version of findIndex that works with a monadic predicate
Hello. I need a function findIndexM, similar to findIndex from the standard module Data.List, but which works with a monadic predicate to test list elements. findIndex :: (a - Bool) - [a] - Maybe Int findIndexM :: (Monad m, Num a) = (t - m Bool) - [t] - m (Maybe a) findIndexM p xs = go 0 xs where go _ [] = return Nothing go n (x:xs) = do res - p x if res then return (Just n) else go (n+1) xs How can this function be rewritten using combinators? Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Wrong Package-URL in regex-tdfa.cabal
Hello. The cabal file for the regex-tddfa-1.1.6 package seems to have an invalid URL for the Package-URL field: Package-URL: http://darcs.haskell.org/packages/regex-unstable/regex-tdfa/ It should be fixed. Regards. Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] looking for tagsoup-parsec examples
Hello. I am looking for some examples of code using Text.HTML.TagSoup.Parsec, from the tagsoup-parsec package. Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] looking for tagsoup-parsec examples
On Mon, Nov 22, 2010 at 02:20:22PM -0200, José Romildo Malaquias wrote: I am looking for some examples of code using Text.HTML.TagSoup.Parsec, from the tagsoup-parsec package. In an attempt to learn how to use tagsoup together with parsec in order to do web scrapping, I rewrote the application that displays the Haskell.org hit count, explained in the Drinking TagSoup by Example tutorial [1]. The source code is attached. First I tried to use tagsoup-parsec [2], but it was not too helpful. Therefore I wrote a few parser combinators myself (inspired by tagsoup-parsec, and the TagSoup, meet Parsec! blog post [3]. I am posting the program here so that other Haskell programmers can comment on it. I would like also to do some suggestions to the author of tagsoup-parsec: a) export more functions, like tagEater, which may be needed in order to define new parsers or parser combinators; I needed them, but they were no usable because they are not exported; b) add more basic parsers and parser combinators (at least the ones I have defined in my program). c) add some examples d) use parsec version 3 [1] http://community.haskell.org/~ndm/darcs/tagsoup/tagsoup.htm [2] http://hackage.haskell.org/package/tagsoup-parsec [3] http://therning.org/magnus/archives/367 Regards, Romildo module Main (main) where import Text.Parsec hiding (satisfy) import Text.HTML.TagSoup (parseTags, Tag(TagText), (~==)) import Text.HTML.Download (openURL) import Data.Char (isDigit) import Data.List (findIndex) main = do src - openURL http://www.haskell.org/haskellwiki/Haskell; let x = tagParse counter (parseTags src) putStrLn $ haskell.org has been hit ++ show x ++ times counter = do skipTo (tag div class=printfooter) count 2 (skipTo (tag p)) s - tagText let ss = words s case findIndex (== times.) ss of Just i - let num = ss !! (i - 1) in return (read (filter isDigit num) :: Int) Nothing - parserZero -- -- tag parser library -- tagParse p ts = either ( error . show ) id $ parse p tagsoup ts tagEater matcher = tokenPrim show (\pos t ts - incSourceLine pos 1) matcher anyTag = tagEater Just satisfy f = tagEater (\t - if f t then Just t else Nothing) tag t = satisfy (~== t) ? show t tagText str = do TagText x - tag (TagText str) return x skipTo p = try p | (anyTag skipTo p) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Tooltips on tree view rows
Hello. I need the gtk_tree_view_set_tooltip_column from Gtk+, but it seems tht it has not been ported to gtk2hs. Is it the case? How can I easily add tooltips to rows in a TreeView? Regards, Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Downloading web page in Haskell
In order to download a given web page, I wrote the attached program. The problem is that the page is not being full downloaded. It is being somehow intettupted. Any clues on how to solve this problem? Romildo module Main where import Network.HTTP (getResponseBody, getRequest, simpleHTTP) openURL x = simpleHTTP (getRequest x) = getResponseBody main = do src - openURL http://www.adorocinema.com/common/search/search_by_film/?criteria=Bourne; writeFile test.html src putStrLn src ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Downloading web page in Haskell
On Sat, Nov 20, 2010 at 10:26:49PM +0100, Daniel Fischer wrote: On Saturday 20 November 2010 21:47:52, Don Stewart wrote: 2010/11/20 José Romildo Malaquias j.romi...@gmail.com: In order to download a given web page, I wrote the attached program. The problem is that the page is not being full downloaded. It is being somehow intettupted. Any clues on how to solve this problem? FWIW, with this url, I get the same problem using the Curl package Just for the record, wget also gets a truncated (at the same point) file, so it's not a Haskell problem. Web browsers like Firefox and Opera does not seem to have the same problem with this web page. I would like to be able to download this page from Haskell. Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ghc panic when compiling blaze-builder
When compiling blaze-builder-0.2.0.1 with ghc-7.0.1 on my ~amd64 gentoo
system, I am getting the shown below.
Any clues?
Romildo
[...]
Building blaze-builder-0.2.0.1...
[1 of 8] Compiling Blaze.ByteString.Builder.Internal (
Blaze/ByteString/Builder/Internal.hs,
dist/build/Blaze/ByteString/Builder/Internal.o )
ghc: panic! (the 'impossible' happened)
(GHC version 7.0.1 for x86_64-unknown-linux):
dsLet: unlifted
AbsBinds
[b{tv aUH} [sk]]
[]
[pe{v axd} [lid] = [b{tv aUH} [sk]] pe{v aUG} [lid]]
pe{v axd} [lid]
:: forall b{tv aUH} [sk]. base:GHC.Ptr.Ptr{tc 33A} b{tv aUH} [sk]
[LclId]
{ {273:19-54}
{273:19-54}
!((pe{v aUG} [lid] :: base:GHC.Ptr.Ptr{tc 33A} b{tv aUH} [sk]))
= {273:30-54}
{273:33-41}
(base:GHC.Ptr.plusPtr{v r4X} [gid]) @ base:GHC.Word.Word8{tc 32U}
@ b{tv aUH} [sk]
pf{v axc} [lid] firstBufSize{v arR} [lid] }
EvBinds{{}}
base:GHC.Base.={v 01P} [gid[ClassOp]]
@ ntghc-prim:GHC.Types.IO{tc 32I}
$dMonad{v aUI} [lid]
@ blaze-builder-0.2.0.1:Blaze.ByteString.Builder.Internal.BuildSignal{tc
rre}
@ bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}
(step0{v arY} [lid]
pf{v axc} [lid] (pe{v axd} [lid] @ base:GHC.Word.Word8{tc 32U}))
(\ (next{v axT} [lid]
::
blaze-builder-0.2.0.1:Blaze.ByteString.Builder.Internal.BuildSignal{tc rre}) -
let {
ds_d15b{v} [lid]
::
blaze-builder-0.2.0.1:Blaze.ByteString.Builder.Internal.BuildSignal{tc rre}
[LclId]
ds_d15b{v} [lid] = next{v axT} [lid] } in
case ds_d15b{v} [lid] {ghc-prim:GHC.Types.IO{tc 32I}
bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}}
of (wild_B1{v} [lid]
::
blaze-builder-0.2.0.1:Blaze.ByteString.Builder.Internal.BuildSignal{tc rre}) {
blaze-builder-0.2.0.1:Blaze.ByteString.Builder.Internal.Done{d rrk}
(rb_d15l{v} [lid]
:: ghc-prim:GHC.Prim.Addr#{(w) tc 33}) -
let {
pf'{v axU} [lid]
:: base:GHC.Ptr.Ptr{tc 33A} base:GHC.Word.Word8{tc 32U}
[LclId]
pf'{v axU} [lid] =
base:GHC.Ptr.Ptr{v rcP} [gid[DataCon]]
@ base:GHC.Word.Word8{tc 32U} rb_d15l{v} [lid] } in
let {
fail_d15c{v} [lid]
:: ghc-prim:GHC.Prim.State#{(w) tc 32q}
ghc-prim:GHC.Prim.RealWorld{(w) tc 31E}
- ghc-prim:GHC.Types.IO{tc 32I}
bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}
[LclId]
fail_d15c{v} [lid] =
\ (ds_d15d{v} [lid]
:: ghc-prim:GHC.Prim.State#{(w) tc 32q}
ghc-prim:GHC.Prim.RealWorld{(w) tc 31E}) -
base:GHC.Base.${v 019} [gid]
@
bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}
@ (ghc-prim:GHC.Types.IO{tc 32I}
bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5})
(base:GHC.Base.return{v 01T} [gid[ClassOp]]
@ ntghc-prim:GHC.Types.IO{tc 32I}
$dMonad{v aUN} [lid]
@
bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5})
(bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.$WChunk{v reF}
[gid[DataConWrapper]]
(mkbs{v axe} [lid] @ base:GHC.Word.Word8{tc 32U} pf'{v
axU} [lid])
k{v arT} [lid]) } in
case base:GHC.Classes.=={v 01L} [gid[ClassOp]]
@ (base:GHC.Ptr.Ptr{tc 33A} base:GHC.Word.Word8{tc 32U})
$dEq{v aUK} [lid]
pf'{v axU} [lid]
pf{v axc} [lid] {ghc-prim:GHC.Types.IO{tc 32I}
bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}}
of (wild_B1{v} [lid] :: ghc-prim:GHC.Bool.Bool{(w) tc 3c}) {
ghc-prim:GHC.Bool.False{(w) d 68} -
fail_d15c{v} [lid] ghc-prim:GHC.Prim.realWorld#{(w) v 0o}
[gid];
ghc-prim:GHC.Bool.True{(w) d 6u} -
base:GHC.Base.return{v 01T} [gid[ClassOp]]
@ ntghc-prim:GHC.Types.IO{tc 32I}
$dMonad{v aUL} [lid]
@
bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}
k{v arT} [lid]
};
blaze-builder-0.2.0.1:Blaze.ByteString.Builder.Internal.BufferFull{d
rri} (rb_d15n{v} [lid]
::
Re: [Haskell-cafe] Tiger compiler in Haskell: annotating abstract syntax tree
On Tue, Jul 20, 2010 at 09:17:15AM +0200, José Pedro Magalhães wrote: 2010/7/19 José Romildo Malaquias j.romi...@gmail.com I am writing here to ask suggestions on how to annotate an ast with types (or any other information that would be relevant in a compiler phase) in Haskell. Indeed I would suggest the method described in our paper: Martijn van Steenbergen, José Pedro Magalhães, and Johan Jeuring. Generic selections of subexpressions. Paper link: http://dreixel.net/research/pdf/gss_draft.pdf Related hackage package: http://hackage.haskell.org/package/Annotations Annotations-0.1 requires base ==4.1.* and parsec ==3.0.*, but I have base-4.2.0.2 and parsec-3.1.0 on my Gentoo Linux system. Would it work with these new versions of base and parsec? Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] List manager and duplicate copies of messsages
Hello. I have noticed that I do not receive duplicate copies of messages from haskell-cafe, although Avoid duplicate copies of messages? is set to No in the mailing list membership configuration. I want the copies because I archive all the mailing list messages with procmail based on the X-BeenThere header line. Has anybody else seen this behaviour, or am I missing anything? Is there any problems with the mailing list manager? Regards, Romildo -- Computer Science Department Universidade Federal de Ouro Preto, Brasil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] List manager and duplicate copies of messsages
On Wed, Jul 21, 2010 at 02:42:37PM +0200, Martijn van Steenbergen wrote: On 7/21/10 12:48, José Romildo Malaquias wrote: Hello. I have noticed that I do not receive duplicate copies of messages from haskell-cafe, although Avoid duplicate copies of messages? is set to No in the mailing list membership configuration. I want the copies because I archive all the mailing list messages with procmail based on the X-BeenThere header line. Has anybody else seen this behaviour, or am I missing anything? Is there any problems with the mailing list manager? You're using gmail. See: http://www.google.com/support/forum/p/gmail/thread?tid=2d5dbc1f28270634 I am talking about answers to messages that I post to haskell-cafe. If somebody reply to my message sending it both to the mailing list and to me, I am receiving only the copy sent to me. The one sent to the mailing list (with the X-BeenThere in the header used for archiving) is not arriving to my inbox. It works with other mailing lists I subscribe with this same email address from gmail. Nontheless I will subscribe with another email address not from gmail and see if it works as expected. Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Test. Ignore.
Please, ignore this message. Romildo -- ___ Surf the Web in a faster, safer and easier way: Download Opera 9 at http://www.opera.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Test. Ignore.
On Wed, Jul 21, 2010 at 12:53:53PM -0300, José Romildo Malaquias wrote: Please, ignore this message. Replying to the list and to the sender, to see if he gets both messages using a non gmail account. Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Test. Ignore.
- Original Message - From: José Romildo Malaquias j.romi...@gmail.com To: José Romildo Malaquias romi...@operamail.com Cc: haskell-cafe@haskell.org Subject: Re: [Haskell-cafe] Test. Ignore. Date: Wed, 21 Jul 2010 13:01:03 -0300 On Wed, Jul 21, 2010 at 12:53:53PM -0300, José Romildo Malaquias wrote: Please, ignore this message. Replying to the list and to the sender, to see if he gets both messages using a non gmail account. I confirm that I received only one copy of the above message, that was sent directly to my email address at operamail.com. I did not receive any copy from the mailing list manager. Romildo (at opera.com) -- ___ Surf the Web in a faster, safer and easier way: Download Opera 9 at http://www.opera.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Test. Ignore.
- Original Message - From: José Romildo Malaquias romi...@operamail.com To: José Romildo Malaquias j.romi...@gmail.com Cc: haskell-cafe@haskell.org Subject: Re: [Haskell-cafe] Test. Ignore. Date: Wed, 21 Jul 2010 13:09:16 -0300 - Original Message - From: José Romildo Malaquias j.romi...@gmail.com To: José Romildo Malaquias romi...@operamail.com Cc: haskell-cafe@haskell.org Subject: Re: [Haskell-cafe] Test. Ignore. Date: Wed, 21 Jul 2010 13:01:03 -0300 On Wed, Jul 21, 2010 at 12:53:53PM -0300, José Romildo Malaquias wrote: Please, ignore this message. Replying to the list and to the sender, to see if he gets both messages using a non gmail account. I confirm that I received only one copy of the above message, that was sent directly to my email address at operamail.com. I did not receive any copy from the mailing list manager. Romildo (at opera.com) That was expected, as by default the Avoid duplicate copies of messages? option is set to Yes in the mailing list membership configuration. Now I have just set it to No, and I expect to receive both copies next time someone from the mailing list replies to all to one of my messages. Romildo at operamail.com -- ___ Surf the Web in a faster, safer and easier way: Download Opera 9 at http://www.opera.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Test. Ignore.
On Wed, Jul 21, 2010 at 01:25:19PM -0300, José Romildo Malaquias wrote: - Original Message - From: José Romildo Malaquias romi...@operamail.com To: José Romildo Malaquias j.romi...@gmail.com Cc: haskell-cafe@haskell.org Subject: Re: [Haskell-cafe] Test. Ignore. Date: Wed, 21 Jul 2010 13:09:16 -0300 - Original Message - From: José Romildo Malaquias j.romi...@gmail.com To: José Romildo Malaquias romi...@operamail.com Cc: haskell-cafe@haskell.org Subject: Re: [Haskell-cafe] Test. Ignore. Date: Wed, 21 Jul 2010 13:01:03 -0300 On Wed, Jul 21, 2010 at 12:53:53PM -0300, José Romildo Malaquias wrote: Please, ignore this message. Replying to the list and to the sender, to see if he gets both messages using a non gmail account. I confirm that I received only one copy of the above message, that was sent directly to my email address at operamail.com. I did not receive any copy from the mailing list manager. Romildo (at opera.com) That was expected, as by default the Avoid duplicate copies of messages? option is set to Yes in the mailing list membership configuration. Now I have just set it to No, and I expect to receive both copies next time someone from the mailing list replies to all to one of my messages. Romildo at operamail.com Replying to all. Romildo at gmail.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Test. Ignore.
- Original Message - From: José Romildo Malaquias j.romi...@gmail.com To: José Romildo Malaquias romi...@operamail.com Cc: haskell-cafe@haskell.org Subject: Re: [Haskell-cafe] Test. Ignore. Date: Wed, 21 Jul 2010 13:33:34 -0300 On Wed, Jul 21, 2010 at 01:25:19PM -0300, José Romildo Malaquias wrote: - Original Message - From: José Romildo Malaquias romi...@operamail.com To: José Romildo Malaquias j.romi...@gmail.com Cc: haskell-cafe@haskell.org Subject: Re: [Haskell-cafe] Test. Ignore. Date: Wed, 21 Jul 2010 13:09:16 -0300 - Original Message - From: José Romildo Malaquias j.romi...@gmail.com To: José Romildo Malaquias romi...@operamail.com Cc: haskell-cafe@haskell.org Subject: Re: [Haskell-cafe] Test. Ignore. Date: Wed, 21 Jul 2010 13:01:03 -0300 On Wed, Jul 21, 2010 at 12:53:53PM -0300, José Romildo Malaquias wrote: Please, ignore this message. Replying to the list and to the sender, to see if he gets both messages using a non gmail account. I confirm that I received only one copy of the above message, that was sent directly to my email address at operamail.com. I did not receive any copy from the mailing list manager. Romildo (at opera.com) That was expected, as by default the Avoid duplicate copies of messages? option is set to Yes in the mailing list membership configuration. Now I have just set it to No, and I expect to receive both copies next time someone from the mailing list replies to all to one of my messages. Romildo at operamail.com Replying to all. Romildo at gmail.com Well, romildo at operamail.com received both copies of the message. So the list manager worked as expected. Romildo at operamail.com -- ___ Surf the Web in a faster, safer and easier way: Download Opera 9 at http://www.opera.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] List manager and duplicate copies of messsages
On Wed, Jul 21, 2010 at 12:18:14PM -0300, José Romildo Malaquias wrote: On Wed, Jul 21, 2010 at 02:42:37PM +0200, Martijn van Steenbergen wrote: On 7/21/10 12:48, José Romildo Malaquias wrote: Hello. I have noticed that I do not receive duplicate copies of messages from haskell-cafe, although Avoid duplicate copies of messages? is set to No in the mailing list membership configuration. I want the copies because I archive all the mailing list messages with procmail based on the X-BeenThere header line. Has anybody else seen this behaviour, or am I missing anything? Is there any problems with the mailing list manager? You're using gmail. See: http://www.google.com/support/forum/p/gmail/thread?tid=2d5dbc1f28270634 I am talking about answers to messages that I post to haskell-cafe. If somebody reply to my message sending it both to the mailing list and to me, I am receiving only the copy sent to me. The one sent to the mailing list (with the X-BeenThere in the header used for archiving) is not arriving to my inbox. It works with other mailing lists I subscribe with this same email address from gmail. Nontheless I will subscribe with another email address not from gmail and see if it works as expected. After conducting the test with an email address from operamail.com, I noticed that with replying to all, I receive two copies at operamail.com and only one at gmail.com. This is intriguing, because I am subscribed to several other mailing lists with the gmail.com address, and I am seeing this behaviour only with the haskell mailing lists. I apologize for the Test thread. Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Tiger compiler in Haskell: annotating abstract syntax tree
Hello. In his book Modern Compilder Implementation in ML, Appel presents a compiler project for the Tiger programming language where type checking and intermediate code generation are intrinsically coupled. There is a function transExp :: Absyn.Exp - (Tree.Exp,Types.Type) that do semantic analysis, translating an expression to the Tree intermediate representation language and also do type checking, calculating the type of the expression. Maybe the compiler can be made more didatic if these phases are separate phases of compilation. The type checker would annotate the abstract syntax tree (ast) with type annotations, that could be used later by the translater to intermediate representation. In an imperative language probably each relevant ast node would have a field for the type annotation, and the type checker would assign the type of the node to this field after computing it. I am writing here to ask suggestions on how to annotate an ast with types (or any other information that would be relevant in a compiler phase) in Haskell. As an example, consider the simplified ast types: data Exp = IntExp Integer | VarExp Symbol | AssignExp Symbol Exp | IfExp Exp Exp (Maybe Exp) | CallExp Symbol [Exp] | LetExp [Dec] Exp data Dec = TypeDec Symbol Ty | FunctionDec Symbol [(Symbol,Symbol)] (Mybe Symbol) Exp | VarDec Symbol (Maybe Symbol) Exp Expressions can have type annotations, but declarations can not. Comments? Regards, Romildo -- Computer Science Department Universidade Federal de Ouro Preto, Brasil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[romi...@malaquias.dhcp-geral: Re: [Haskell-cafe] Tiger compiler in Haskell: annotating abstract syntax tree]
Forgot the attachment.
Romildo
---BeginMessage---
On Mon, Jul 19, 2010 at 01:51:57PM -0400, Job Vranish wrote:
Martijn van Steenbergen has a good blog post that describes the method I
generally use:
http://martijn.van.steenbergen.nl/journal/2010/06/24/generically-adding-position-information-to-a-datatype/
In his example he annotates the expression tree with position information,
but you can use the same method to add type annotations, or whatever you
want.
After a quick read at Martijn blog article I've written the attached
test program, which works.
But I am not succeeding in deriving Show for the data types. Any help?
Romildo
2010/7/19 José Romildo Malaquias j.romi...@gmail.com
Hello.
In his book Modern Compilder Implementation in ML, Appel presents a
compiler project for the Tiger programming language where type checking
and intermediate code generation are intrinsically coupled.
There is a function
transExp :: Absyn.Exp - (Tree.Exp,Types.Type)
that do semantic analysis, translating an expression to the Tree
intermediate representation language and also do type checking,
calculating the type of the expression.
Maybe the compiler can be made more didatic if these phases are separate
phases of compilation.
The type checker would annotate the abstract syntax tree (ast) with type
annotations, that could be used later by the translater to intermediate
representation.
In an imperative language probably each relevant ast node would have a
field for the type annotation, and the type checker would assign the
type of the node to this field after computing it.
I am writing here to ask suggestions on how to annotate an ast with
types (or any other information that would be relevant in a compiler
phase) in Haskell.
As an example, consider the simplified ast types:
data Exp
= IntExp Integer
| VarExp Symbol
| AssignExp Symbol Exp
| IfExp Exp Exp (Maybe Exp)
| CallExp Symbol [Exp]
| LetExp [Dec] Exp
data Dec
= TypeDec Symbol Ty
| FunctionDec Symbol [(Symbol,Symbol)] (Mybe Symbol) Exp
| VarDec Symbol (Maybe Symbol) Exp
Expressions can have type annotations, but declarations can not.
Comments?
---End Message---
module Main where
newtype Fix f = In { out :: f (Fix f) }
newtype AnnFix x f = AnnFix { runAnnFix :: (x, f (AnnFix x f)) }
data ExpF r
= Num Integer
| Add r r
| Mul r r
| If r r r
type BareExp = Fix ExpF
eval :: BareExp - Integer
eval (In (Num i)) = i
eval (In (Add x y)) = eval x + eval y
eval (In (Mul x y)) = eval x * eval y
eval (In (If t x y)) | eval t == 0 = eval y
| otherwise = eval x
e = In (Add (In (Num 7)) (In (Num 8)))
type Pos = Int
type PosExp = AnnFix Pos ExpF
aEval (AnnFix (_, e)) =
case e of
Num i - i
Add x y - aEval x + aEval y
Mul x y - aEval x * aEval y
If t x y | aEval t == 0 - aEval y
| otherwise - aEval x
ae = AnnFix (3, Add (AnnFix (1, Num 7)) (AnnFix (5, Num 8)))
main = do print (eval e)
print (aEval ae)
___
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[Haskell-cafe] Haskell and Standard ML modules
Hello. I am writing a Haskell program based on some guidelines written for Standard ML (The Tiger compiler from the Modern Compiler Implementation in ML book). The author uses modules for abstracting things like specifities of the taraget machine. For intance, there is a general Frame signature that abstracts the frame representation which depends on the target machine. For each target machine there is a structure compliant to that signature. For instante MipsFrame, PentiumFrame and SparcFrames would be structures implementing the Frame signature. Many parts of the program just see the Frame signature. Is there any guidelines on how to achieve somethying similar to this in Haskell? Regards, Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Physical equality
Is there in Haskell a non monadic function of type a - a - Bool which test for physical equality of two values? It would return True if only if both values are the same object in memory. For instance: value1 = good value2 = good eq value1 value2 = False value1 = good value2 = value1 eq value1 value2 = True Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Tiger compiler: variable escaping analysis phase
On Tue, Jun 22, 2010 at 04:44:09PM +0200, Vo Minh Thu wrote: 2010/6/22 José Romildo Malaquias j.romi...@gmail.com: On Tue, Jun 22, 2010 at 02:54:08PM +0200, Vo Minh Thu wrote: 2010/6/22 José Romildo Malaquias j.romi...@gmail.com: Hello. I have been teaching an introductory course on compiler construction to our undergraduates students using Appel's Modern Compiler Implementation in Java. There are also versions of the book in ML and C. The books explain how to write a compiler for the Tiger programming language. Now I want to implement a Tiger compiler in Haskell. The lexer and parser (built with the help of alex and happy) and the type checker are already working. Next step is implementing a variable escape analysis phase, needed for the intermediate code generator. The objective of this phase is to find out if each variable escapes or not. In general an escaping variable should be allocated in the stack frame (in memory). Non escaping variables may be allocated in the stack frame or in a register. Generally, a variable escapes if it is passed by reference, its address is taken (using C's operator, for instance), or it is accessed from a nested function. Only the last is possible with Tiger. The approach adopted by Appel in his books is easy: a muttable field in the abstract syntax of variable declarations, of for expressions, and of function formal parameters, which introduce new variables, is used to collect the escaping information of the variable. In the ML version of the book this is a reference to boolean (bool ref). Initially, in a conservative approach, the reference is initialized to true. In the variable escaping analysis phase of the compiler, a function findEscape looks for escaping variables and record this information in the escape fields of the abstract syntax. To do this the entire abstract syntax tree is traversed looking for escaping uses of every variable, and, when found, the field is set to true. findEscape uses a symbol table to accomplish its work, binding variable names to a reference to boolean (the same reference used in the abstract syntax tree). When processing a variable declaraction, for instance, it inserts the variable name into the symbol table, binding it to its escaping field. When processing an expression which is a simple variable, if the variable occurs in a nested function, its binding in the symbol table is set to true. This reflects directly in the abstract syntax tree of the variable declaration, as the escape field in the variable declaration and the binding in the symbol table are the same reference to bool. I am look for good ways to implement the variable escaping analysis phase in Haskell, which is a pure language. I see two alternatives: 1) adopt the same approach as Appel used in his ML version of the compiler: use a mutable reference in the IO monad (Data.IORef) to hold the variable escaping information, and write everything inside the IO monad 2) build a new abstract syntax tree with updated information regarding variable escaping The second option is more elegant in my point of view, but would be much less efficient than the first one. So I want to know what advices Haskell programmers has to me about implementing this phase of the Tiger compiler in Haskell. Hi, I think there is a third way to do what you describe (if I understood everything). You can use a Writer monad (basically a state monad where the state is never read, only written to). Essentially you walk the tree and record the information you want (a mapping from variable name to a boolean 'does-escape'). That information is threaded through the tree-walking functions. The information you record is the underlying monoid of the Writer monad. The 'does-escape' information should be available for each variable at the point the variable is introduced (a variable declaration or a formal parameter in a function declaration, for instance). If this information is collected in another data structure that is not the abstract syntax tree, it may be difficult to access the 'does-escape' information when needed. I was thinking 'accessing when needed' was just a lookup into that other datastructure (i.e. a map). As someone said, and related to your second solution, this analysis and the resulting mapping can be put pack into the tree. I.e. instead of data Tree = ... you have data Tree a = ... and the 'a' can be whatever you want, including the 'does-escape' boolean value. In this line I thought about using a mapping from a pair consisting of the variable name and its position in the source code, to the 'does-escape' boolean. The findEscape function would construct this mapping while traversing the abstract syntax tree. Yes, that was what I
[Haskell-cafe] Tiger compiler: variable escaping analysis phase
Hello. I have been teaching an introductory course on compiler construction to our undergraduates students using Appel's Modern Compiler Implementation in Java. There are also versions of the book in ML and C. The books explain how to write a compiler for the Tiger programming language. Now I want to implement a Tiger compiler in Haskell. The lexer and parser (built with the help of alex and happy) and the type checker are already working. Next step is implementing a variable escape analysis phase, needed for the intermediate code generator. The objective of this phase is to find out if each variable escapes or not. In general an escaping variable should be allocated in the stack frame (in memory). Non escaping variables may be allocated in the stack frame or in a register. Generally, a variable escapes if it is passed by reference, its address is taken (using C's operator, for instance), or it is accessed from a nested function. Only the last is possible with Tiger. The approach adopted by Appel in his books is easy: a muttable field in the abstract syntax of variable declarations, of for expressions, and of function formal parameters, which introduce new variables, is used to collect the escaping information of the variable. In the ML version of the book this is a reference to boolean (bool ref). Initially, in a conservative approach, the reference is initialized to true. In the variable escaping analysis phase of the compiler, a function findEscape looks for escaping variables and record this information in the escape fields of the abstract syntax. To do this the entire abstract syntax tree is traversed looking for escaping uses of every variable, and, when found, the field is set to true. findEscape uses a symbol table to accomplish its work, binding variable names to a reference to boolean (the same reference used in the abstract syntax tree). When processing a variable declaraction, for instance, it inserts the variable name into the symbol table, binding it to its escaping field. When processing an expression which is a simple variable, if the variable occurs in a nested function, its binding in the symbol table is set to true. This reflects directly in the abstract syntax tree of the variable declaration, as the escape field in the variable declaration and the binding in the symbol table are the same reference to bool. I am look for good ways to implement the variable escaping analysis phase in Haskell, which is a pure language. I see two alternatives: 1) adopt the same approach as Appel used in his ML version of the compiler: use a mutable reference in the IO monad (Data.IORef) to hold the variable escaping information, and write everything inside the IO monad 2) build a new abstract syntax tree with updated information regarding variable escaping The second option is more elegant in my point of view, but would be much less efficient than the first one. So I want to know what advices Haskell programmers has to me about implementing this phase of the Tiger compiler in Haskell. Regards, Romildo -- Computer Science Department Universidade Federal de Ouro Preto, Brazil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Tiger compiler: variable escaping analysis phase
On Tue, Jun 22, 2010 at 02:30:04PM +0100, Stephen Tetley wrote: Hello Doaitse Swierstra has a Tiger compiler written in Haskell + UUAG as a demonstration for UUAG attribute grammar system. The package on Hackage only contains the derived source - i.e not the original attribute grammar code, but the generated Haskell source after running UUAG on the *.ag files. http://hackage.haskell.org/package/tiger You could try contacting Doaitse Swierstra for the original UUAG source. I have found the sources at http://www.cs.uu.nl/wiki/HUT/WebHome. What is provided is an implementation of a compiler front-end and type checker for Andrew Appel's Tiger language. The variable escaping phase (needed only to decide where variables would be allocated in the back-end) is not implemented. At least I could not find it in a quick view. Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Tiger compiler: variable escaping analysis phase
On Tue, Jun 22, 2010 at 02:54:08PM +0200, Vo Minh Thu wrote: 2010/6/22 José Romildo Malaquias j.romi...@gmail.com: Hello. I have been teaching an introductory course on compiler construction to our undergraduates students using Appel's Modern Compiler Implementation in Java. There are also versions of the book in ML and C. The books explain how to write a compiler for the Tiger programming language. Now I want to implement a Tiger compiler in Haskell. The lexer and parser (built with the help of alex and happy) and the type checker are already working. Next step is implementing a variable escape analysis phase, needed for the intermediate code generator. The objective of this phase is to find out if each variable escapes or not. In general an escaping variable should be allocated in the stack frame (in memory). Non escaping variables may be allocated in the stack frame or in a register. Generally, a variable escapes if it is passed by reference, its address is taken (using C's operator, for instance), or it is accessed from a nested function. Only the last is possible with Tiger. The approach adopted by Appel in his books is easy: a muttable field in the abstract syntax of variable declarations, of for expressions, and of function formal parameters, which introduce new variables, is used to collect the escaping information of the variable. In the ML version of the book this is a reference to boolean (bool ref). Initially, in a conservative approach, the reference is initialized to true. In the variable escaping analysis phase of the compiler, a function findEscape looks for escaping variables and record this information in the escape fields of the abstract syntax. To do this the entire abstract syntax tree is traversed looking for escaping uses of every variable, and, when found, the field is set to true. findEscape uses a symbol table to accomplish its work, binding variable names to a reference to boolean (the same reference used in the abstract syntax tree). When processing a variable declaraction, for instance, it inserts the variable name into the symbol table, binding it to its escaping field. When processing an expression which is a simple variable, if the variable occurs in a nested function, its binding in the symbol table is set to true. This reflects directly in the abstract syntax tree of the variable declaration, as the escape field in the variable declaration and the binding in the symbol table are the same reference to bool. I am look for good ways to implement the variable escaping analysis phase in Haskell, which is a pure language. I see two alternatives: 1) adopt the same approach as Appel used in his ML version of the compiler: use a mutable reference in the IO monad (Data.IORef) to hold the variable escaping information, and write everything inside the IO monad 2) build a new abstract syntax tree with updated information regarding variable escaping The second option is more elegant in my point of view, but would be much less efficient than the first one. So I want to know what advices Haskell programmers has to me about implementing this phase of the Tiger compiler in Haskell. Hi, I think there is a third way to do what you describe (if I understood everything). You can use a Writer monad (basically a state monad where the state is never read, only written to). Essentially you walk the tree and record the information you want (a mapping from variable name to a boolean 'does-escape'). That information is threaded through the tree-walking functions. The information you record is the underlying monoid of the Writer monad. The 'does-escape' information should be available for each variable at the point the variable is introduced (a variable declaration or a formal parameter in a function declaration, for instance). If this information is collected in another data structure that is not the abstract syntax tree, it may be difficult to access the 'does-escape' information when needed. In this line I thought about using a mapping from a pair consisting of the variable name and its position in the source code, to the 'does-escape' boolean. The findEscape function would construct this mapping while traversing the abstract syntax tree. The function that generates the intermediate representation of the program would be given the abstract syntax tree and the escaping mapping as arguments. When traversing the abstract syntax tree to generate code, it would consult the escaping mapping to determine if a varable escapes or not, when allocating a variable. The variable name and its position are available from the abstract syntax tree. Are you suggesting that the Writer monad would be used to construct a data structure like the escaping mapping I mentioned above? Anyway, the second option sounds better than the first one as you don't have to rely
Re: [Haskell-cafe] Tiger compiler: variable escaping analysis phase
On Tue, Jun 22, 2010 at 10:01:37AM -0300, Felipe Lessa wrote: On Tue, Jun 22, 2010 at 09:33:22AM -0300, José Romildo Malaquias wrote: In the variable escaping analysis phase of the compiler, a function findEscape looks for escaping variables and record this information in the escape fields of the abstract syntax. To do this the entire abstract syntax tree is traversed looking for escaping uses of every variable, and, when found, the field is set to true. findEscape uses a symbol table to accomplish its work, binding variable names to a reference to boolean (the same reference used in the abstract syntax tree). When processing a variable declaraction, for instance, it inserts the variable name into the symbol table, binding it to its escaping field. When processing an expression which is a simple variable, if the variable occurs in a nested function, its binding in the symbol table is set to true. This reflects directly in the abstract syntax tree of the variable declaration, as the escape field in the variable declaration and the binding in the symbol table are the same reference to bool. Idea of pure algorithm: 1) Update the symbol table itself, that is: instead of using (a) Map Symbol (IORef Bool) use (b) Map Symbol Bool. This doesn't change the complexity of the algorithm as searching and updating have the same complexity for many data structures (maps and hashtables, for example). In reality, you don't need to use a Map at all. Just use (c) Set Symbol and symbols not in the set do not escape. Using (a) gives you O(n log k) for this step, where n is the size of the AST and k is the number of symbols. On the other hand, (c) gives you O(n log e), where e is the number of escaping symbols. These solutions would not work because they do not deal with scopes of variables. In a Tiger program (as in most programming languges) a variable name can be reused many times to refer to different variables, and each variable can escape. Maybe a set of pairs containing the variable name and its position in the source code (available from the abstract syntax tree) would be a good idea. Then the code generator would traverse the abstract syntax tree and, when needed, use this set to find out whether a variable escapes. 2) After doing the whole analysis, use a function 'addEscapeInfo' to process the whole pure AST again adding information about escaped symbols. This is O(n log e) as well. If the variable escaping analysis is done and its result is made available in another data structure, there would be no need to add the escaping information back to the abstract syntax tree. The second option is more elegant in my point of view, but would be much less efficient than the first one. While O(n log e) is better than O(n log k), probably the constants in the pure algorithm are higher than their impure counterparts. I guess you could also try to write: 1) Take an 'AST e' into 'AST (STRef s Bool, e)' in O(n). 2) Use the impure algorithm inside ST monad in O(n log k). 3) Take 'AST (STRef s Bool, e)' into 'AST (Bool, e)' in O(n). 4) 'runST' on the above steps to get a pure function from 'AST e' into 'AST (Bool, e)'. The ST monad has the same runtime overhead as IO. Steps 1) and 3) are used to hide the ST monad from the rest of the compiler. Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Get data from HTML pages
Hello. I am porting to Haskell a Java application I have written to manage collections of movies. Currently the application has an option to indirectly import movie data from web pages. For that first the user should access the page in a web browser. Then the user should copy the rendered text in the web browser into an import window in my application and click an import button. In response the application parses the given text and collects any relevant data it knows about, using regular expressions. For instance, to get the director information from a movie in the AllCenter web site I use the following regular expression: ^Direção:\s+(.+)$ I want to modify this scheme in order to eliminate the need to copy the rendered text from a web browser. Instead my application should download and parse the HTML page directly. Which libraries are available in Haskell that would make it easy to get content information from a HTML document, in the way described above? Regards, Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Pretty printing a tree
Hello. I would like to pretty print a tree in a way that its structure is easily perceived. For instance, consider the declarations: data Node a = Node a [Node a] type Tree a = [ Node a ] t = [ Node a [ Node b [] , Node c [ Node c1 [] , Node c2 [] ] , Node d [ Node d1 [ Node d1a [] ] , Node d2 [] ] ] ] Then the resulting of pretty printing the given tree would be something like the following: a | +-+ ||| bcd || +---++---+ | || | c1 c2 d1 d2 | d1a There is the module Text.PrettyPrint.HughesPJ, but it lacks examples on how to use the pretty print combinators, and it is not well docomented. I would like to see solutions for this problem, or clues on how to solve it. Regards, José Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
