Re: [Haskell-beginners] Beginners Digest, Vol 104, Issue 16

15 Mar 2017

      [image: Inline image 1]
"Problem Opening Wizard"

I've Eclipse "Version: Neon.2 Release (4.6.2) Build id: 20161208-0600"
installed on macOS El Capitan 10.11.6.

"The selected wizard could not be started.

Plug-in net.sf.eclipsefp.haskell.ui was unable to load class
net.sf.eclipsefp.haskell.ui.wizards.NewHaskellProjectWizard.
An error occurred while automatically activating bundle
net.sf.eclipsefp.haskell.ui (482)."

Albert.

Anyone has the same problem and solved it?

Thanks.

On Thu, Feb 23, 2017 at 1:10 AM,  wrote:
...
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Today's Topics:
1. Re:  Type error when using splitOn function. (Francesco Ariis)
   2. Re:  Type error when using splitOn function. (S. H. Aegis)
   3.  How to link two Types (PICCA Frederic-Emmanuel)
   4. Re:  How to link two Types (David McBride)
   5. Re:  How to link two Types (PICCA Frederic-Emmanuel)
   6. Re:  How to link two Types (David McBride)
----------------------------------------------------------------------
Message: 1
Date: Wed, 22 Feb 2017 14:31:16 +0100
From: Francesco Ariis 
To: beginners@haskell.org
Subject: Re: [Haskell-beginners] Type error when using splitOn
        function.
Message-ID: <20170222133116.GA14860@casa.casa>
Content-Type: text/plain; charset=us-ascii
On Wed, Feb 22, 2017 at 09:02:22PM +0900, S. H. Aegis wrote:
...
Thank you so much.
--makeRxDxList :: Functor f => f Text -> f [Text]
Above signature comes from ghci using command :t
My intention is
makeRxDxList :: Text -> [[Text]]
but, I got error, and try several times and below codes pass a complier.
makeRxDxList rowRxDx = fmap (\x -> splitOn (pack ",") x) rowRxDx  -- This
code pass a compile.
and then, I run ghci, type :t, and got below signature.
makeRxDxList :: Functor f => f Text -> f [Text]
Your kind answer says, I cannot help using fmap. right? ^^;
Thanks again.
Then this:
makeRxDxList :: Text -> [[Text]]
    makeRxDxList rowRxDx = fmap f (lines rowRxDx)
                -- you imported Prelude hiding map, so we will use fmap
        where
              f :: Text -> [Text]
              f x = splitOn (pack ",") x
should do (at least it typechecks).
GHC errors may not have the prettiest formatting ever, but they are
very useful, the most important bits being line & column of the offending
expression plus the "expected this but got that" part; get acquainted
with them!
------------------------------
Message: 2
Date: Wed, 22 Feb 2017 22:41:10 +0900
From: "S. H. Aegis" 
To: The Haskell-Beginners Mailing List - Discussion of primarily
        beginner-level topics related to Haskell 
Subject: Re: [Haskell-beginners] Type error when using splitOn
        function.
Message-ID:

Content-Type: text/plain; charset="utf-8"
It works !!! (^O^)
Thank you so much.
Have a nice day~!
2017-02-22 22:31 GMT+09:00 Francesco Ariis :
...
On Wed, Feb 22, 2017 at 09:02:22PM +0900, S. H. Aegis wrote:
...
Thank you so much.
--makeRxDxList :: Functor f => f Text -> f [Text]
Above signature comes from ghci using command :t
My intention is
makeRxDxList :: Text -> [[Text]]
but, I got error, and try several times and below codes pass a
complier.
makeRxDxList rowRxDx = fmap (\x -> splitOn (pack ",") x) rowRxDx  --
This
code pass a compile.
and then, I run ghci, type :t, and got below signature.
makeRxDxList :: Functor f => f Text -> f [Text]
Your kind answer says, I cannot help using fmap. right? ^^;
Thanks again.
Then this:
makeRxDxList :: Text -> [[Text]]
    makeRxDxList rowRxDx = fmap f (lines rowRxDx)
                -- you imported Prelude hiding map, so we will use fmap
        where
              f :: Text -> [Text]
              f x = splitOn (pack ",") x
should do (at least it typechecks).
GHC errors may not have the prettiest formatting ever, but they are
very useful, the most important bits being line & column of the offending
expression plus the "expected this but got that" part; get acquainted
with them!
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Re: [Haskell-beginners] Beginners Digest, Vol 104, Issue 16

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