[Haskell-cafe] Newbie type question for wxHaskell learner

[b1g3ar5]

Nearly - the first suggestion doesn't work because each es needs a new
panel I can't use the same one each time.

The second suggestion doesn't quite work because the x in [text :=
contents x] is not in scope of the \p function.

Thanks.

N


On Jan 7, 6:29 pm, Daniel Fischer <daniel.is.fisc... at googlemail.com>
wrote:
> On Friday 07 January 2011 19:01:43, b1g3ar5 wrote:
>
>
>
>
>
>
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>
>
> > Thanks for your reply but it doesn't quite solve the problem. This:
>
> > plist <- mapM (\x-> (panel nb [])) my_list
>
> > returns [Panel()] and works as you say, but:
>
> > elist <- mapM (\x-> (textCtrl (panel nb []) [text := contents x]))
> > my_list
>
> > still won't work because the function panel returns a IO (Panel()) and
> > so won't do as a parameter to textCtrl.
>
> > I can get round this by applying mapM to a list of the indices (of
> > my_list and plist:
>
> > elist <- mapM (\ix-> (textCtrl (plist!!ix) [text := contents (my_list!!
> > ix)])) [1..4]
>
> > but this seems a bit crap. There must be a neat way of doing this.
>
> Depends on the semantics of panel, maybe
>
> do whatever
>    p <- panel nb []
>    es <- mapM (\x -> textCtrl p [text := contents x]) my_list
>    moreWith es
>
> does what you want. If panel has side effects you need for every item in
> the list,
>
> do whatever
>    es <- mapM (\x -> panel nb [] >>=
>                      \p -> textCtrl p [text:=contents x]) my_list
>    moreWith es
>
> ought to do it.
>
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