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Today's Topics:
1. Re: database, list result, extraction and conversion
(Francesco Ariis)
2. Re: Regex (David McBride)
3. Re: Regex (mike h)
4. Re: Regex (mike h)
5. Re: (SPAM 3)Re: database, list result, extraction and
conversion (Damien Mattei)
6. Re: (SPAM 3)Re: database, list result, extraction and
conversion (Francesco Ariis)
----------------------------------------------------------------------
Message: 1
Date: Thu, 6 Dec 2018 14:07:40 +0100
From: Francesco Ariis <[email protected]>
To: [email protected]
Subject: Re: [Haskell-beginners] database, list result, extraction and
conversion
Message-ID: <[email protected]>
Content-Type: text/plain; charset=us-ascii
On Thu, Dec 06, 2018 at 12:16:08PM +0100, Damien Mattei wrote:
> *Main> show s
> "Only {fromOnly = \"-04.3982\"}"
>
> but how can i get the String "-04.3982" ? and after converting it to a
> Float?
I suspect that "fromOnly" accessor will do!
http://hackage.haskell.org/package/mysql-simple-0.4.5/docs/Database-MySQL-Simple.html#t:Only
------------------------------
Message: 2
Date: Thu, 6 Dec 2018 08:44:45 -0500
From: David McBride <[email protected]>
To: Haskell Beginners <[email protected]>
Subject: Re: [Haskell-beginners] Regex
Message-ID:
<CAN+Tr43AVKi5nZNvQApKhHzPu-B0Br=uwnjxmpdso7e9hea...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
In Haskell virtually everyone uses parser combinator libraries like parsec,
megaparsec, or attoparsec depending on their needs.
Many people ask this question and are then disappointed when they can't
find a definitively standard regex library to use. That's because they are
barely needed.
That's not to say that there are no such libraries
There are. But I personally couldn't suggest any as I have not been
compelled to use one in many years.
On Thu, Dec 6, 2018, 05:38 mike h <[email protected] wrote:
> Hi,
>
> Which package is the most popular and/or easy to used for dealing with
> regular expressions?
> My regex is quite simple and I just need to get 2 or 3 capture groups from
> the result.
>
> Many thanks
>
> Mike
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
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Message: 3
Date: Thu, 6 Dec 2018 13:53:44 +0000 (UTC)
From: mike h <[email protected]>
To: Haskell Beginners <[email protected]>, The Haskell-Beginners
Mailing List - Discussion of primarily beginner-level topics related
to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] Regex
Message-ID: <[email protected]>
Content-Type: text/plain; charset="utf-8"
:) I get a real buzz out of writing parser combinators. So, perversely - if
only to broaden my Haskell knowledge, I decided to try using regexs. LOL
I'll see where this takes me!
Thanks
Mike
On Thursday, 6 December 2018, 13:45:21 GMT, David McBride
<[email protected]> wrote:
In Haskell virtually everyone uses parser combinator libraries like parsec,
megaparsec, or attoparsec depending on their needs.
Many people ask this question and are then disappointed when they can't find a
definitively standard regex library to use. That's because they are barely
needed.
That's not to say that there are no such libraries There are. But I personally
couldn't suggest any as I have not been compelled to use one in many years.
On Thu, Dec 6, 2018, 05:38 mike h <[email protected] wrote:
Hi,
Which package is the most popular and/or easy to used for dealing with regular
expressions?
My regex is quite simple and I just need to get 2 or 3 capture groups from the
result.
Many thanks
Mike
_______________________________________________
Beginners mailing list
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http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
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------------------------------
Message: 4
Date: Thu, 6 Dec 2018 13:53:44 +0000 (UTC)
From: mike h <[email protected]>
To: Haskell Beginners <[email protected]>, The Haskell-Beginners
Mailing List - Discussion of primarily beginner-level topics related
to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] Regex
Message-ID: <[email protected]>
Content-Type: text/plain; charset="utf-8"
:) I get a real buzz out of writing parser combinators. So, perversely - if
only to broaden my Haskell knowledge, I decided to try using regexs. LOL
I'll see where this takes me!
Thanks
Mike
On Thursday, 6 December 2018, 13:45:21 GMT, David McBride
<[email protected]> wrote:
In Haskell virtually everyone uses parser combinator libraries like parsec,
megaparsec, or attoparsec depending on their needs.
Many people ask this question and are then disappointed when they can't find a
definitively standard regex library to use. That's because they are barely
needed.
That's not to say that there are no such libraries There are. But I personally
couldn't suggest any as I have not been compelled to use one in many years.
On Thu, Dec 6, 2018, 05:38 mike h <[email protected] wrote:
Hi,
Which package is the most popular and/or easy to used for dealing with regular
expressions?
My regex is quite simple and I just need to get 2 or 3 capture groups from the
result.
Many thanks
Mike
_______________________________________________
Beginners mailing list
[email protected]
http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
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------------------------------
Message: 5
Date: Thu, 6 Dec 2018 15:54:45 +0100
From: Damien Mattei <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] (SPAM 3)Re: database, list result,
extraction and conversion
Message-ID: <[email protected]>
Content-Type: text/plain; charset=utf-8
if it was so easy!
GHCi, version 8.4.3: http://www.haskell.org/ghc/ :? for help
Prelude> fromOnly [Only {fromOnly = "-04.3982"}]
<interactive>:1:12: error: Not in scope: data constructor ‘Only’
and in a program:
bd_rows <- query conn qry_head (Only (name::String))
putStrLn $ show bd_rows
putStrLn $ show name
let resLst = []
let noBD = fromOnly bd_rows
forM_ bd_rows $ \(Only a) ->
putStrLn $ Data.Text.unpack a
Prelude> :load UpdateSidonie
[1 of 1] Compiling Main ( UpdateSidonie.hs, interpreted )
UpdateSidonie.hs:93:25: error:
• Couldn't match expected type ‘Only a’
with actual type ‘[Only Text]’
• In the first argument of ‘fromOnly’, namely ‘bd_rows’
In the expression: fromOnly bd_rows
In an equation for ‘noBD’: noBD = fromOnly bd_rows
• Relevant bindings include
noBD :: a (bound at UpdateSidonie.hs:93:9)
|
93 | let noBD = fromOnly bd_rows
| ^^^^^^^
Failed, no modules loaded.
Le 06/12/2018 14:07, Francesco Ariis a écrit :
> On Thu, Dec 06, 2018 at 12:16:08PM +0100, Damien Mattei wrote:
>> *Main> show s
>> "Only {fromOnly = \"-04.3982\"}"
>>
>> but how can i get the String "-04.3982" ? and after converting it to a
>> Float?
>
> I suspect that "fromOnly" accessor will do!
>
> http://hackage.haskell.org/package/mysql-simple-0.4.5/docs/Database-MySQL-Simple.html#t:Only
>
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
--
[email protected], [email protected], UNS / OCA / CNRS
------------------------------
Message: 6
Date: Thu, 6 Dec 2018 17:10:00 +0100
From: Francesco Ariis <[email protected]>
To: [email protected]
Subject: Re: [Haskell-beginners] (SPAM 3)Re: database, list result,
extraction and conversion
Message-ID: <[email protected]>
Content-Type: text/plain; charset=utf-8
On Thu, Dec 06, 2018 at 03:54:45PM +0100, Damien Mattei wrote:
> if it was so easy!
Damien, you must heed the compiler!
> UpdateSidonie.hs:93:25: error:
> • Couldn't match expected type ‘Only a’
> with actual type ‘[Only Text]’
> • In the first argument of ‘fromOnly’, namely ‘bd_rows’
> In the expression: fromOnly bd_rows
> In an equation for ‘noBD’: noBD = fromOnly bd_rows
> • Relevant bindings include
> noBD :: a (bound at UpdateSidonie.hs:93:9)
> |
> 93 | let noBD = fromOnly bd_rows
> | ^^^^^^^
> Failed, no modules loaded.
So you applied `fromOnly` to `bd_rows`. fromOnly has type
fromOnly :: Only a -> a
Now GHC is complaining:
• I was expecting ‘Only a’
but you gave me ‘[Only Text]’
So either call "head" on [Only Text] (unsafe!) or map over it.
See if it works and if not, fire again here
-F
------------------------------
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