[Haskell-beginners] No instance for Show arising from a use in “main” level

[T. Andrea Moruno Rodriguez]

Hi!

Yes.

Thanks I resolved my problem. The explanation is here:

http://stackoverflow.com/questions/39112380/no-instance-for-show-arising-from-a-use-in-main-level?noredirect=1#comment65572477_39112380


2016-08-23 20:23 GMT-04:00 Imants Cekusins <imantc at gmail.com>:

> Hello Tatiana,
>
> these signatures do not look good:
>
> main :: (Show (IO J2s)) => IO()
>
> test :: (Show (IO J2s)) => String -> IO()
>
> testParser :: (Show (IO J2s)) => IO()
> ​
>
> constraints are used to specify type variables. IO J2s looks like * (a
> fixed type).
>
> what errors do you see without these constraints?
>
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