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-ml@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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