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<interactive>:2:1: error:
• Ambiguous type variable ‘f0’ arising from a use of ‘<$>’
prevents the constraint ‘(Functor f0)’ from being solved.
Relevant bindings include
it :: f0 (Maybe a) (bound at <interactive>:2:1)
Probable fix: use a type annotation to specify what ‘f0’ should be.
These potential instances exist:
instance Functor (Either a) -- Defined in ‘Data.Either’
instance Functor IO -- Defined in ‘GHC.Base’
instance Functor Maybe -- Defined in ‘GHC.Base’
...plus two others
...plus 34 instances involving out-of-scope types
(use -fprint-potential-instances to see them all)
• In the expression: Just <$> _
In an equation for ‘it’: it = Just <$> _
<interactive>:2:10: error:
• Found hole: _ :: f0 a
Where: ‘f0’ is an ambiguous type variable
‘a’ is a rigid type variable bound by
the inferred type of it :: f0 (Maybe a)
at <interactive>:2:1-10
• In the second argument of ‘(<$>)’, namely ‘_’
In the expression: Just <$> _
In an equation for ‘it’: it = Just <$> _
• Relevant bindings include
it :: f0 (Maybe a) (bound at <interactive>:2:1)
Valid substitutions include
error :: forall a. GHC.Stack.Types.HasCallStack => [Char] -> a
(imported from ‘Prelude’ (and originally defined in ‘GHC.Err’))
errorWithoutStackTrace :: forall a. [Char] -> a
(imported from ‘Prelude’ (and originally defined in ‘GHC.Err’))
Nothing :: forall a. Maybe a
(imported from ‘Prelude’ (and originally defined in ‘GHC.Base’))
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