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List:       haskell-beginners
Subject:    Re: [Haskell-beginners] Showing Types
From:       Alex Rozenshteyn <rpglover64 () gmail ! com>
Date:       2016-03-08 15:26:21
Message-ID: CALm==BWHyVZCZKj2QXOATmvSTxPWT1z9JsZAKiVuD=_WaAty1w () mail ! gmail ! com
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And you also run into trouble with typeOf Nothing.

On Tue, Mar 8, 2016 at 10:09 AM, Alex Rozenshteyn <rpglover64@gmail.com>
wrote:

> > But it works on concrete types, not functions.
>
> Isn't the problem type variables, not functions?
>
> Prelude Data.Typeable> :set -XScopedTypeVariables
> Prelude Data.Typeable> let fun x = case x of {Just (i::Int) -> i + 1;
> Nothing -> 0}
> Prelude Data.Typeable> :t fun
> fun :: Maybe Int -> Int
> Prelude Data.Typeable> typeOf fun
> Maybe Int -> Int
>
>

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<div dir="ltr">And you also run into trouble with <span \
style="font-family:monospace,monospace">typeOf Nothing</span><font \
face="arial,helvetica,sans-serif">.</font><br></div><div class="gmail_extra"><br><div \
class="gmail_quote">On Tue, Mar 8, 2016 at 10:09 AM, Alex Rozenshteyn <span \
dir="ltr">&lt;<a href="mailto:rpglover64@gmail.com" \
target="_blank">rpglover64@gmail.com</a>&gt;</span> wrote:<br><blockquote \
class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc \
solid;padding-left:1ex"><div dir="ltr"><span class=""><div>&gt; But it works on \
concrete types, not functions.<br><br></div></span>Isn&#39;t the problem type \
variables, not functions?<br><span \
style="font-family:monospace,monospace"><br>Prelude Data.Typeable&gt; :set \
-XScopedTypeVariables<br>Prelude Data.Typeable&gt; let fun x = case x of {Just \
(i::Int) -&gt; i + 1; Nothing -&gt; 0}<br>Prelude Data.Typeable&gt; :t fun<br>fun :: \
Maybe Int -&gt; Int<br>Prelude Data.Typeable&gt; typeOf fun<br>Maybe Int -&gt; \
Int</span><br><br></div> </blockquote></div><br></div>



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