2

Hello after doing the parsing with a script in Haskell I got a file with the 'appearance' of lists of strings. However when I call the file content with the function getContents or hGetContents, ie, reading the contents I get something like: String with lines (schematically what I want is: "[" aaa "," bbb "" ccc "]" -> ["aaa", "bbb" "ccc"]). I have tried with the read function but without results. I need to work with these lists of strings to concatenating them all in a single list.

I'm using the lines function, but I think it only 'works' one line at a time, doesn't it? What I need is a function that verify if an element of a line is repeted on other line. If I could have a list of a list of strings it could be easier (but what I have is a line of a string that looks like a list of strings) Regards Thanks.

Improve this question
5
  • 3
    To help us answer questions like this better, always provide at least an error message. "Without results" is incredibly vague, and from your description the problem could be pretty much anything. Commented Dec 26, 2010 at 20:17
  • Can you provide some sample input? I'm having a hard time understanding. Are you looking to turn each line of the file into a list of strings, so that you end up with is [[String]]? Commented Dec 28, 2010 at 6:45
  • I have a file with the results of a lot of inscriptions (of participants) in a future meeting. This file has the structure of CSV (comma separated values). After making parsing the contents of the file becomes somtehing like this: ["name1","[email protected]","phone1","age1","company1"] ["name2","[email protected]","phone2","age2","company2"] ["name1","[email protected]","phone1","age1","company1"] ["name3","[email protected]","phone3","age3","company3"] Now I need to handle data entry and the best would be something like: Commented Dec 28, 2010 at 14:54
  • [["name1","[email protected]","phone1","age1","company1"],["name2","[email protected]","phone2","age2","company2"],["name1","[email protected]","phone1","age1","company1"],["name3","[email protected]","phone3","age3","company3"]] something like :: [[String]]. But what I have above is :: String splited into multiple lines. This string can be divided into lines - lines function - but each line ["namex","[email protected]","phonex","agex","companyx"] is a string. I need to convert the line to a list of strings :: [String] and all the content of the file :: [[String]]. Commented Dec 28, 2010 at 14:56
  • If I use the function read (read line:: [String]) for each line I get error due to lack of \ "For example: - To check if there are repeated entries to verify that the email address is being duplicated in another row. - to see how many participants also belong to a particular company. Thanks Commented Dec 28, 2010 at 14:56

3 Answers 3

Reset to default
2

I have tried with the read function but without results

Just tested, and it works fine:

Prelude> read "[\"aaa\",\"bbb\",\"ccc\"]" :: [String]
["aaa","bbb","ccc"]

Note that you need to give the return type explicitly, since it can't be determined from the type of the argument.

Improve this answer
Sign up to request clarification or add additional context in comments.

1 Comment

Thank you, this works fine; but I need get the content of the file and it doesn't have the '\' (slash); how can I read (convert) from a line? I mean, all the content of the file is treated as a string divided by lines (in each line we have something that looks like a list of strings but is a string).
0

I think the function you are looking for is the lines function from Data.List (reexported by the Prelude) that breaks up a multi-line string into a list of strings.

Improve this answer

1 Comment

Thanks Cactus, I'm using the lines function, but I think it only 'works' one line at a time, doesn't it? What I need is a function that verify if an element of a line is repeted on other line. If I could have a list of a list of strings it could be easier (but what I have is a line of a string that looks like a list of strings) Regards
0

in my understanding, what you can do is

create a function that receives a list of lists, each list is a line of the entire string, of the argument passed in, and checks if a element of a line occurs in other line.

then, this function passes the entire string, separated by lines using [lines][1].

Improve this answer

1 Comment

Thanks, but how can I check if an element is in other line; because I only can handle one line at a time? Example: \n first input = unlines eachLine \n where allLines = lines input; \n eachLine = map listStr allLines \n Another thing is that if I create a function that receives a list of list (of strings) but I only can pass a string (each line) (Please note that in the code above \n is for break the line)

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.