Re: [Haskell-cafe] Example code won't compile
OK. Thanks, everyone. Michael --- On Fri, 5/15/09, Krzysztof Skrzętnicki wrote: From: Krzysztof Skrzętnicki Subject: Re: [Haskell-cafe] Example code won't compile To: "michael rice" Cc: "Lennart Augustsson" , "haskell-cafe@haskell.org" Date: Friday, May 15, 2009, 9:55 PM The one important line is > import Control.Monad.Error It adds dependancy on mtl package, which is not used by default (contrary to 'base' package, which includes Monad, System and IO modules). With --make GHC adds it automatically. Therefore $ ghc -package mtl ex14.hs compiles fine. I'd recommend using --make. In rare occasions when there is a namespace clash between packages one can simply hide offending packages or specify preferred ones. Best regards Christopher Skrzętnicki ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Example code won't compile
The one important line is > import Control.Monad.Error It adds dependancy on mtl package, which is not used by default (contrary to 'base' package, which includes Monad, System and IO modules). With --make GHC adds it automatically. Therefore $ ghc -package mtl ex14.hs compiles fine. I'd recommend using --make. In rare occasions when there is a namespace clash between packages one can simply hide offending packages or specify preferred ones. Best regards Christopher Skrzętnicki ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Example code won't compile
This example compiles fine without --make. What's the difference?
Michael
==
{- Author: Jeff Newbern
Maintainer: Jeff Newbern
Time-stamp:
License: GPL
-}
{- DESCRIPTION
Example 13 - Using the List monad
Usage: Compile the code and execute the resulting program
with various arguments. Each argument will produce
a list of possible parses of the argument as a decimal
number, a hexadecimal number or a word.
Try: ./ex13 34 f3 bean
./ex13 food f00d
./ex13 beef 10 "n!"
./ex13 "why?" "(punctuation)"
-}
import Monad
import System
import Char
-- we can parse three different types of terms
data Parsed = Digit Integer | Hex Integer | Word String deriving Show
-- attempts to add a character to the parsed representation of a hex digit
parseHexDigit :: Parsed -> Char -> [Parsed]
parseHexDigit (Hex n) c = if isHexDigit c then
return (Hex ((n*16) + (toInteger (digitToInt c
else
mzero
parseHexDigit _ _ = mzero
-- attempts to add a character to the parsed representation of a decimal digit
parseDigit :: Parsed -> Char -> [Parsed]
parseDigit (Digit n) c = if isDigit c then
return (Digit ((n*10) + (toInteger (digitToInt c
else
mzero
parseDigit _ _ = mzero
-- attempts to add a character to the parsed representation of a word
parseWord :: Parsed -> Char -> [Parsed]
parseWord (Word s) c = if isAlpha c then
return (Word (s ++ [c]))
else
mzero
parseWord _ _ = mzero
-- tries to parse the digit as a hex value, a decimal value and a word
-- the result is a list of possible parses
parse :: Parsed -> Char -> [Parsed]
parse p c = (parseHexDigit p c) `mplus` (parseDigit p c) `mplus` (parseWord p c)
-- parse an entire String and return a list of the possible parsed values
parseArg :: String -> [Parsed]
parseArg s = do init <- (return (Hex 0)) `mplus` (return (Digit 0)) `mplus`
(return (Word ""))
foldM parse init s
-- show the original string and all possible parses for the string
showResult :: String -> IO ()
showResult s = do putStr s
putStr ": "
print (parseArg s)
-- prints possible parsed values for command-line arguments
main :: IO ()
main = do args <- getArgs
mapM_ showResult args
-- END OF FILE
--- On Fri, 5/15/09, Lennart Augustsson wrote:
From: Lennart Augustsson
Subject: Re: [Haskell-cafe] Example code won't compile
To: "michael rice"
Cc: "haskell-cafe@haskell.org"
Date: Friday, May 15, 2009, 7:25 PM
--make
-- Lennart (iPhone)
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Example code won't compile
nowgate: > Why won't this code compile? > [mich...@localhost ~]$ ghc ex14.hs -o ex14 Missing --make I'd also add -O2, but I'm like that. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Example code won't compile
Why won't this code compile?
Michael
===
{- Author: Jeff Newbern
Maintainer: Jeff Newbern
Time-stamp:
License: GPL
-}
{- DESCRIPTION
Example 14 - Using the IO monad
Usage: Compile the code to produce a poor replacement for
the standard Unix "tr" command.
Try: cat file | ./ex14 "aeiou" "X"
cat file | ./ex14 " " "_"
./ex14 "abc"
-}
import Monad
import System
import IO
import Control.Monad.Error
-- translate char in set1 to corresponding char in set2
translate :: String -> String -> Char -> Char
translate [] _ c = c
translate (x:xs) [] c = if x == c then ' ' else translate xs [] c
translate (x:xs) [y] c = if x == c then y else translate xs [y] c
translate (x:xs) (y:ys) c = if x == c then y else translate xs ys c
-- translate an entire string
translateString :: String -> String -> String -> String
translateString set1 set2 str = map (translate set1 set2) str
usage :: IOError -> IO ()
usage e = do putStrLn "Usage: ex14 set1 set2"
putStrLn "Translates characters in set1 on stdin to the
corresponding"
putStrLn "characters from set2 and writes the translation to
stdout."
-- translates stdin to stdout based on commandline arguments
main :: IO ()
main = (do [set1,set2] <- getArgs
contents <- hGetContents stdin
putStr $ translateString set1 set2 contents)
`catchError` usage
-- END OF FILE
=
[mich...@localhost ~]$ ghc ex14.hs -o ex14
ex14.o: In function `rF8_info':
(.text+0x48): undefined reference to
`mtlzm1zi1zi0zi2_ControlziMonadziError_zdf17_closure'
ex14.o: In function `sGp_info':
(.text+0x861): undefined reference to
`mtlzm1zi1zi0zi2_ControlziMonadziError_zdf17_closure'
ex14.o: In function `sGp_info':
(.text+0x91d): undefined reference to
`__stginit_mtlzm1zi1zi0zi2_ControlziMonadziError_'
ex14.o: In function `rF8_info':
(.text+0x50): undefined reference to
`mtlzm1zi1zi0zi2_ControlziMonadziErrorziClass_zdp1MonadError_info'
ex14.o: In function `sGp_info':
(.text+0x869): undefined reference to
`mtlzm1zi1zi0zi2_ControlziMonadziErrorziClass_catchError_info'
ex14.o: In function `rF8_srt':
(.data+0x0): undefined reference to
`mtlzm1zi1zi0zi2_ControlziMonadziError_zdf17_closure'
ex14.o: In function `Main_main_srt':
(.data+0x6c): undefined reference to
`mtlzm1zi1zi0zi2_ControlziMonadziError_zdf17_closure'
collect2: ld returned 1 exit status
[mich...@localhost ~]$
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
