<br><div class="gmail_quote">On Thu, Dec 11, 2008 at 09:57, Neil Mitchell <span dir="ltr"><<a href="mailto:ndmitchell@gmail.com">ndmitchell@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
HI Pedro,<br>
<div><div></div><div class="Wj3C7c"><br>
> Would this help?<br>
><br>
>> {-# LANGUAGE ScopedTypeVariables #-}<br>
>> {-# LANGUAGE FlexibleContexts #-}<br>
>><br>
>> module Data.Generics.Builders (empty) where<br>
>><br>
>> import Data.Data<br>
>> import Data.Generics.Aliases (extB)<br>
>><br>
>> -- | Construct the empty value for a datatype. For algebraic datatypes,<br>
>> the<br>
>> -- leftmost constructor is chosen.<br>
>> empty :: forall a. Data a => a<br>
>> empty = general<br>
>> `extB` char<br>
>> `extB` int<br>
>> `extB` integer<br>
>> `extB` float<br>
>> `extB` double where<br>
>> -- Generic case<br>
>> general :: Data a => a<br>
>> general = fromConstrB empty (indexConstr (dataTypeOf general) 1)<br>
>><br>
>> -- Base cases<br>
>> char = '\NUL'<br>
>> int = 0 :: Int<br>
>> integer = 0 :: Integer<br>
>> float = 0.0 :: Float<br>
>> double = 0.0 :: Double<br>
<br>
</div></div>Yep, that should do it!</blockquote><div><br>It's slated for release with the next version of the SYB library, so in a near future you'll only need to import it.<br>
<br>
<br>
Cheers,<br>
Pedro</div></div><br>