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Today's Topics:
1. Re: Type error when using splitOn function. (S. H. Aegis)
----------------------------------------------------------------------
Message: 1
Date: Wed, 22 Feb 2017 21:02:22 +0900
From: "S. H. Aegis" <shae...@gmail.com>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <beginners@haskell.org>
Subject: Re: [Haskell-beginners] Type error when using splitOn
function.
Message-ID:
<cajp-nqxxwhmz-rjn0n_7gkaqe7w4qmjasjdx6ext8ptykuk...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
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.
2017-02-22 18:35 GMT+09:00 Francesco Ariis <fa...@ariis.it>:
> On Wed, Feb 22, 2017 at 05:33:01PM +0900, S. H. Aegis wrote:
> > Hello.
> > I'm new to Haskell and this is the first time I use Data.Text module.
> > And using stack on OSX 10.12.3
> > I'm try several times, but fail. and I don't understand what error
> message
> > says.
> > How can I fix this?
> > Thank you a lot.
>
> Hello SH, Text.map has signature `(Char -> Char) -> Text -> Text`, so
> I expect you to need fmap too if the return value of makeRxDxList has
> type f [Text]
>
> makeRxDxList rowRxDx = fmap _ rowRxDx
> -- or base map
>
> _ is a hole and if the compiler will tell you which function needs to
> go there, in this case one with signature `Text -> [Text]`.
>
> Does that help? If not, provide makeRxDxList signature and a brief
> description so it's easier to diagnose the problem
> -F
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--
Sok Ha, CHANG
Dr. Chang's Clinic. #203. 503-23. AmSa-Dong, GangDong-Gu, Seoul.
Tel: +82-2-442-7585
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