Is there already a lib to parse a line of string with a pattern and generate key-value map or a record?

Magicloud Magiclouds

17 Apr 2019 17 Apr '19

5:29 a.m.

Hi, I saw this function in some web tools, pretty useful when parsing log or so. So I wonder if Haskell has similar libs already. Sample: Input line: "2019/04/17 17:27 User magicloud runs command ls." Pattern: "${year}/${month}/${day} ${hour}:${minute} User ${username} runs command ${command}." Output: toList [ ("year", "2019"), ("month", "04") , etc ] -- 竹密岂妨流水过山高哪阻野云飞 And for G+, please use magiclouds#gmail.com.

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Vanessa McHale

17 Apr 17 Apr

8:11 a.m.

I would use Dhall: https://dhall-lang.org/ (I can answer questions but the documentation is reasonably good) Cheers, Vanessa On 4/17/19 4:29 AM, Magicloud Magiclouds wrote:

...

Hi,

I saw this function in some web tools, pretty useful when parsing log or so. So I wonder if Haskell has similar libs already.

Sample:

Input line: "2019/04/17 17:27 User magicloud runs command ls."

Pattern: "${year}/${month}/${day} ${hour}:${minute} User ${username} runs command ${command}."

Output: toList [ ("year", "2019"), ("month", "04") , etc ]

-- 竹密岂妨流水过山高哪阻野云飞

And for G+, please use magiclouds#gmail.com. _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

Magicloud Magiclouds

10:29 a.m.

Sorry, I am not sure how this relates to my thought? I want a parsing tool. On Wed, Apr 17, 2019 at 8:11 PM Vanessa McHale wrote:

...

I would use Dhall: https://dhall-lang.org/

(I can answer questions but the documentation is reasonably good)

Cheers, Vanessa

On 4/17/19 4:29 AM, Magicloud Magiclouds wrote:

...
Hi,

I saw this function in some web tools, pretty useful when parsing log or so. So I wonder if Haskell has similar libs already.

Sample:

Input line: "2019/04/17 17:27 User magicloud runs command ls."

Pattern: "${year}/${month}/${day} ${hour}:${minute} User ${username} runs command ${command}."

Output: toList [ ("year", "2019"), ("month", "04") , etc ]

-- 竹密岂妨流水过山高哪阻野云飞

And for G+, please use magiclouds#gmail.com. _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

_______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

-- 竹密岂妨流水过山高哪阻野云飞 And for G+, please use magiclouds#gmail.com.

Станислав Черничкин

9:46 a.m.

I think specific formats can be parsed with attoparsec (Data.Attoparsec.Text): p = do year <- yearP char '/' month <- monthP char '/' .... return (year, month, ...) You may also use cassava to parse csv-like files, or Frames for type-safe parsing. With Frames you may custom readers ( http://acowley.github.io/Frames/#orgfa57664 ) with complex pattern-matching, this will require typing skills though. ср, 17 апр. 2019 г. в 12:30, Magicloud Magiclouds < magicloud.magiclouds@gmail.com>:

...

Hi,

I saw this function in some web tools, pretty useful when parsing log or so. So I wonder if Haskell has similar libs already.

Sample:

Input line: "2019/04/17 17:27 User magicloud runs command ls."

Pattern: "${year}/${month}/${day} ${hour}:${minute} User ${username} runs command ${command}."

Output: toList [ ("year", "2019"), ("month", "04") , etc ]

-- 竹密岂妨流水过山高哪阻野云飞

And for G+, please use magiclouds#gmail.com. _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

-- Sincerely, Stanislav Chernichkin.

Magicloud Magiclouds

10:32 a.m.

Thanks. I am familiar with this kind of usage (attoparsec). But it is still somehow complex and not flexible. Let me see what Frame can do. On Wed, Apr 17, 2019 at 9:46 PM Станислав Черничкин wrote:

...

I think specific formats can be parsed with attoparsec (Data.Attoparsec.Text):

p = do year <- yearP char '/' month <- monthP char '/' .... return (year, month, ...)

You may also use cassava to parse csv-like files, or Frames for type-safe parsing. With Frames you may custom readers ( http://acowley.github.io/Frames/#orgfa57664 ) with complex pattern-matching, this will require typing skills though.

ср, 17 апр. 2019 г. в 12:30, Magicloud Magiclouds :

...
Hi,

I saw this function in some web tools, pretty useful when parsing log or so. So I wonder if Haskell has similar libs already.

Sample:

Input line: "2019/04/17 17:27 User magicloud runs command ls."

Pattern: "${year}/${month}/${day} ${hour}:${minute} User ${username} runs command ${command}."

Output: toList [ ("year", "2019"), ("month", "04") , etc ]

-- 竹密岂妨流水过山高哪阻野云飞

And for G+, please use magiclouds#gmail.com. _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

-- Sincerely, Stanislav Chernichkin.

-- 竹密岂妨流水过山高哪阻野云飞 And for G+, please use magiclouds#gmail.com.

Frank Dedden

11:27 a.m.

I think you're looking for a scanf (well known in C) like function. A quick search give me: https://hackage.haskell.org/package/scanf https://hackage.haskell.org/package/xformat I haven't used either of them, so I can't recommend one. Regards, Frank Dedden On Wed, Apr 17, 2019 at 10:32:07PM +0800, Magicloud Magiclouds wrote:

...

Thanks. I am familiar with this kind of usage (attoparsec). But it is still somehow complex and not flexible.

Let me see what Frame can do.

On Wed, Apr 17, 2019 at 9:46 PM Станислав Черничкин wrote:

...
I think specific formats can be parsed with attoparsec (Data.Attoparsec.Text):

p = do year <- yearP char '/' month <- monthP char '/' .... return (year, month, ...)

You may also use cassava to parse csv-like files, or Frames for type-safe parsing. With Frames you may custom readers ( http://acowley.github.io/Frames/#orgfa57664 ) with complex pattern-matching, this will require typing skills though.

ср, 17 апр. 2019 г. в 12:30, Magicloud Magiclouds :

...
Hi,

I saw this function in some web tools, pretty useful when parsing log or so. So I wonder if Haskell has similar libs already.

Sample:

Input line: "2019/04/17 17:27 User magicloud runs command ls."

Pattern: "${year}/${month}/${day} ${hour}:${minute} User ${username} runs command ${command}."

Output: toList [ ("year", "2019"), ("month", "04") , etc ]

-- 竹密岂妨流水过山高哪阻野云飞

And for G+, please use magiclouds#gmail.com. _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

-- Sincerely, Stanislav Chernichkin.

-- 竹密岂妨流水过山高哪阻野云飞

And for G+, please use magiclouds#gmail.com. _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

Magicloud Magiclouds

18 Apr 18 Apr

11:13 a.m.

scanf looks interesting. Closer to my case. Thanks. Neil, the formation looks OK in GMail. The lib gives me some other thoughts. Thanks. On Wed, Apr 17, 2019 at 11:24 PM Frank Dedden wrote:

...

I think you're looking for a scanf (well known in C) like function. A quick search give me: https://hackage.haskell.org/package/scanf https://hackage.haskell.org/package/xformat

I haven't used either of them, so I can't recommend one.

Regards, Frank Dedden

On Wed, Apr 17, 2019 at 10:32:07PM +0800, Magicloud Magiclouds wrote:

...
Thanks. I am familiar with this kind of usage (attoparsec). But it is still somehow complex and not flexible.

Let me see what Frame can do.

On Wed, Apr 17, 2019 at 9:46 PM Станислав Черничкин wrote:

...
I think specific formats can be parsed with attoparsec (Data.Attoparsec.Text):

p = do year <- yearP char '/' month <- monthP char '/' .... return (year, month, ...)

You may also use cassava to parse csv-like files, or Frames for type-safe parsing. With Frames you may custom readers ( http://acowley.github.io/Frames/#orgfa57664 ) with complex pattern-matching, this will require typing skills though.

ср, 17 апр. 2019 г. в 12:30, Magicloud Magiclouds :

...
Hi,

I saw this function in some web tools, pretty useful when parsing log or so. So I wonder if Haskell has similar libs already.

Sample:

Input line: "2019/04/17 17:27 User magicloud runs command ls."

Pattern: "${year}/${month}/${day} ${hour}:${minute} User ${username} runs command ${command}."

Output: toList [ ("year", "2019"), ("month", "04") , etc ]

-- 竹密岂妨流水过山高哪阻野云飞

And for G+, please use magiclouds#gmail.com. _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

-- Sincerely, Stanislav Chernichkin.

-- 竹密岂妨流水过山高哪阻野云飞

And for G+, please use magiclouds#gmail.com. _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

-- 竹密岂妨流水过山高哪阻野云飞 And for G+, please use magiclouds#gmail.com.

Neil Mayhew

17 Apr 17 Apr

12:07 p.m.

I’m a fan of |regex-applicative|. It’s a combinator library modelled on the parsec family but because it parses only regular languages rather than context-free ones, it’s a bit simpler to use and is a better match for some tasks. It uses |OverloadedStrings| to make it easier to include literal string matches and provides a non-greedy repeating combinator called |few| that avoids having to specify exclusive matches. I think it solves this problem quite nicely: |{-# LANGUAGE OverloadedStrings #-} import Text.Regex.Applicative -- This is just <*> with right associativity (<&>) :: Applicative f => f (a -> b) -> f a -> f b (<&>) = (<*>) infixr 3 <&> type Item = (String, String) item :: String -> RE Char ([Item] -> [Item]) item key = (:) . (,) key <$> few anySym -- ${year}/${month}/${day} ${hour}:${minute} User ${username} runs command ${command}. pattern :: RE Char [Item] pattern = item "year" <* "/" <&> item "month" <* "/" <&> item "day" <* " " <&> item "hour" <* ":" <&> item "minute" <* " User " <&> item "username" <* " runs command " <&> item "command" <* "." <&> pure [] input :: String input = "2019/04/17 17:27 User magicloud runs command ls." output :: Maybe [Item] output = match pattern input -- Just [("year","2019"),("month","04"),("day","17"),("hour","17"),("minute","27"),("username","magicloud"),("command","ls")] | (Also available as a gist https://gist.github.com/neilmayhew/e4fc90b7eaeb7bbcfeb6d6938544ecc9.) Obviously the combinator version is less compact and therefore could be considered less readable, but the implementation details could probably be tweaked a bit. It would also be relatively easy to write a quasi-quoter that turns the original input syntax (with |${variable}|) into the equivalent I’ve shown here.

Neil Mayhew

12:14 p.m.

I'm sorry, the formatting got mangled in my last message, because I was using MarkdownHere. I'll try again without converting it to HTML. I'm a fan of `regex-applicative`. It's a combinator library modelled on the parsec family but because it parses only regular languages rather than context-free ones, it's a bit simpler to use and is a better match for some tasks. It uses `OverloadedStrings` to make it easier to include literal string matches and provides a non-greedy repeating combinator called `few` that avoids having to specify exclusive matches. I think it solves this problem quite nicely: ```haskell {-# LANGUAGE OverloadedStrings #-} import Text.Regex.Applicative -- This is just <*> with right associativity (<&>) :: Applicative f => f (a -> b) -> f a -> f b (<&>) = (<*>) infixr 3 <&> type Item = (String, String) item :: String -> RE Char ([Item] -> [Item]) item key = (:) . (,) key <$> few anySym -- ${year}/${month}/${day} ${hour}:${minute} User ${username} runs command ${command}. pattern :: RE Char [Item] pattern = item "year" <* "/" <&> item "month" <* "/" <&> item "day" <* " " <&> item "hour" <* ":" <&> item "minute" <* " User " <&> item "username" <* " runs command " <&> item "command" <* "." <&> pure [] input :: String input = "2019/04/17 17:27 User magicloud runs command ls." output :: Maybe [Item] output = match pattern input -- Just [("year","2019"),("month","04"),("day","17"),("hour","17"),("minute","27"),("username","magicloud"),("command","ls")] ``` (Also available as a [gist](https://gist.github.com/neilmayhew/e4fc90b7eaeb7bbcfeb6d6938544ecc9).) Obviously the combinator version is less compact and therefore could be considered less readable, but the implementation details could probably be tweaked a bit. It would also be relatively easy to write a quasi-quoter that turns the original input syntax (with `${variable}`) into the equivalent I've shown here.

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Frank Dedden
Magicloud Magiclouds
Neil Mayhew
Vanessa McHale
Станислав Черничкин