[Haskell-cafe] Pattern matching with OverloadedLists

[Vlatko Basic]

I was only wondering why doesn't that work.
The two functions were just an example of how I thought OverloadedLists 
should/could work.

I got an answer on irc that ':' constructor is not desugared, but I expected it is.
Compiler can see when overloading is for "real" list and skip it, preserving 
performance.



> -------- Original Message --------
> Subject: Re: [Haskell-cafe] Pattern matching with OverloadedLists
> From: Alejandro Serrano Mena <trupill at gmail.com>
> To: vlatko.basic at gmail.com
> Cc: haskell-cafe <Haskell-cafe at haskell.org>
> Date: 06/11/15 16:38
>
>
> You need to write `toList` in both branches:
>
> f (toList -> ('9':_)) = 1
> f (toList -> ('1':_)) = 2
>
> 2015-11-06 16:20 GMT+01:00 Vlatko Basic <vlatko.basic at gmail.com 
> <mailto:vlatko.basic at gmail.com>>:
>
>     Hello Cafe,
>
>     wiki for OverloadedLists says that
>
>     g  [x,y,z]  =  ...
>
>     is treated as
>
>     g  (toList->  [x,y,z])  =
>
>
>     Shouldn't this work? Both 'f's should be treated the same.
>
>     f :: Text -> Int
>     f (toList -> ('9':_)) = 1   -- OK
>     f                 ('1':_)  = 2   -- Couldn't match expected type ‘Text’
>     with actual type ‘[Char]’
>
>     (OverloadedStrings is also on)
>
>     Am I missing something?
>
>     br,
>     vlatko
>
>
>
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