Bugs item #1156554, was opened at 2005-03-04 10:03
Message generated for change (Comment added) made by simonmar
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=108032&aid=1156554&group_id=8032
Category: GHCi
Group: 6.4
Status: Open
Resolution: None
Priority: 4
Submitted By: Simon Marlow (simonmar)
Assigned to: Nobody/Anonymous (nobody)
Summary: GHCi: No instance for (Show (IO ()))
Initial Comment:
>From Wolfgang Thaller:
This behaviour (from today's stable branch) is slightly
confusing:
> Prelude> print id
>
> Top level:
> No instance for (Show (IO ()))
> arising from use of `print' at Top level
> Probable fix: add an instance declaration for
(Show (IO ()))
> In a 'do' expression: print it
>
> <interactive>:1:0:
> No instance for (Show (a -> a))
> arising from use of `print' at <interactive>:1:0-4
> Probable fix: add an instance declaration for
(Show (a -> a))
> In the definition of `it': it = print id
The second message makes sense, but the first one
doesn't. Also, what's
the difference between "Top level" and "<interactive>:1:0"?
----------------------------------------------------------------------
>Comment By: Simon Marlow (simonmar)
Date: 2005-04-29 09:52
Message:
Logged In: YES
user_id=48280
Futher to this bug report, here's another expression that
gives a terrible error message:
Prelude Random> randomRIO (1,2)
Top level:
No instance for (Show (IO a))
arising from use of `print' at Top level
Probable fix: add an instance declaration for (Show (IO a))
In a 'do' expression: print it
----------------------------------------------------------------------
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=108032&aid=1156554&group_id=8032
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