[Haskell-beginners] beginner question

[Luca Ciciriello]

Thanks. 

 

import Text.ParserCombinators.Parsec 

 

simple = between (char '"') (char '"') (many (satisfy (/= '"')))


multiple = sepBy simple (char ',') 
total     = sepBy multiple (char '@') 

 

str2lsts :: String -> [[String]]
str2lsts str= case parse total "" str of
                   Left err -> error (show err)
                   Right lsts -> lsts

 

solves my problem. As you can see I've replaced '§' with '@' and now all works fine.

 

Luca. 
 
> From: daniel.is.fischer at web.de
> To: beginners at haskell.org
> Subject: Re: [Haskell-beginners] beginner question
> Date: Fri, 30 Oct 2009 15:46:33 +0100
> 
> Am Freitag 30 Oktober 2009 14:40:13 schrieb Luca Ciciriello:
> > Hi all.
> >
> > Just a very basic question.
> >
> >
> >
> > I need to write a function str2lsts :: String -> [[String]] in order to
> > transorm a string like:
> >
> >
> >
> > "\"1\",\"cat\",\"dog\"§\"2\",\"duck\",\"goose\""
> >
> >
> >
> > in the list of lists:
> >
> >
> >
> > [["1","cat","dog"],["2","duck","goose"]]
> >
> >
> >
> > I've tried to mix recursion, pattern matching and list comprehension, but
> > the obtained result was embarrassing complex (> 20 lines of awful code). I
> > think that a more simple solution certainly exists.
> >
> 
> splitOnToken :: Eq a => a -> [a] -> [[a]]
> splitOnToken t xs
> = case break (== t) xs of
> (hd,tl) -> hd:case tl of
> (_:r@(_:_)) -> splitOnToken t r
> _ -> []
> 
> str2lsts = map (map read . splitOnToken ',') . splitOnToken '§'
> 
> if things weren't enclosed in quotation marks inside the string, it would be the nicer
> 
> map (splitOnToken ',') . splitOnToken '§'
> 
> , provided of course, neither ',' nor '§' are valid characters for the target strings.
> 
> import Text.ParserCombinators.Parsec
> 
> simple = between (char '"') (char '"') (many (staisfy (/= '"')))
> -- alternative: simple = char '"' >> manyTill anyChar (char '"')
> 
> multiple = sepBy simple (char ',')
> 
> total = sepBy multiple (char '§')
> 
> str2lsts str
> = case parse total "" str of
> Left err -> error (show err)
> Right lsts -> lsts
> 
> >
> >
> >
> > Thanks in advance for any idea.
> >
> >
> >
> > Luca
> 
> 
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