[Haskell-cafe] still wrestling with io

[Seth Gordon]

Martin DeMello wrote:
> Code here: http://zem.novylen.net/anagrid.html
> 
> I've got an instance of IO appearing unexpectedly and I can't figure
> out where from. It throws up the following error:
> 
> $ ghc --make test.hs
> Chasing modules from: test.hs
> Compiling Main             ( test.hs, test.o )
> 
> test.hs:38:15:
>    Couldn't match `StaticText ()' against `IO (StaticText ())'
>      Expected type: StaticText ()
>      Inferred type: IO (StaticText ())
>    In the application `staticText p [text := (labelText a b)]'
>    In the definition of `textOf':
>        textOf p a b = staticText p [text := (labelText a b)]

According to the
http://wxhaskell.sourceforge.net/doc/Graphics.UI.WX.Controls.html page,
"staticText" has the type signature "Window a -> [Prop (StaticText ())]
-> IO (StaticText ())".  Your textOf function has the type signature
"Panel () -> String -> Anagrams -> StaticText ()".  Your textOf
*definition*, therefore, something of type "StaticText()" left side and
 type "IO (StaticText ())" on the right.  The compiler doesn't like that.