Hi! Yes. Thanks I resolved my problem. The explanation is here: http://stackoverflow.com/questions/39112380/no-instance-for-show-arising-fro... 2016-08-23 20:23 GMT-04:00 Imants Cekusins :

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?