[Haskell-beginners] help designing types for a gsl fit

[David McBride]

If you look at the type of labelNew

GlibString string => Maybe string -> IO Label

If you look at the instances for GlibString, they could be Text or
[Char].  You have to decide which.  The fact that you are using
Nothing does not tell you the entire final type.  It could be Maybe
[Char], or Maybe Text.  Even though the choice seems arbitrary in this
instance, you have to decide which it is.  So try this.

lprog <- G.labelNew (Nothing :: Maybe [Char])

On Fri, Jun 23, 2017 at 3:22 AM, Agustin Larreinegabe
<alarreine at gmail.com> wrote:
> Hello,
> I'm trying to install an application Termite - Debug but I get this error in
> line 929:14
>
> when it try to do this
>
>
>
>              lprog <- G.labelNew Nothing
>
>
> The error says:
>
> Could not deduce (glib-0.13.4.1:System.Glib.UTFString.GlibString string0)
> arising from a use of ‘G.labelNew’ from the context (D.Rel c v a s) bound by
> the type signature for sourceWindowCreate :: D.Rel c v a s => RSourceView c
> a u -> IO G.Widget at Debug/SourceView.hs:913:23-73 instance
> glib-0.13.4.1:System.Glib.UTFString.GlibString [Char] -- Defined in
> ‘glib-0.13.4.1:System.Glib.UTFString’ In a stmt of a 'do' block: lprog <-
> G.labelNew Nothing In the expression: do { vbox <- G.vBoxNew False 0;
> G.widgetShow vbox; spec <- getIORef svInputSpec ref; code <- codeWinNew
> spec; .... } In an equation for ‘sourceWindowCreate’: sourceWindowCreate ref
> = do { vbox <- G.vBoxNew False 0; G.widgetShow vbox; spec <- getIORef
> svInputSpec ref; cabal: Error: some packages failed to install:
>
> I really don't know how to proceed, I'm new with Haskell
>
>
> Thanks in advance.
>
>
> -----------------
> Agustin Larreinegabe
>
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