[Haskell-cafe] Reverse Show instance

[Markus Läll]

If you have nested type, then it usually makes sense to have Show defined
for the inside types, too, but it's not a requirement. Technically, only
when you call 'show' for something in the data type you are defining Show
for, *then* you need a Show instance defined for that inside-type.

On Fri, May 20, 2011 at 12:15 AM, Andrew Coppin <andrewcoppin at btinternet.com
> wrote:

> On 19/05/2011 10:11 PM, Artyom Kazak wrote:
>
>> And I can declare an instance for (x, y) which does NOT implies (Show x):
>>
>> instance Show (x, y) where
>> show _ = "I'm tuple! Hooray!"
>>
>
> Ah. So it's a feature.
>
> Fortunately I refactored the program where this came up, so it's no longer
> an issue. I just wanted to see whether or not it was a bug.
>
> PS. Wouldn't such an instance require FlexibleContexts or something?
>
>
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-- 
Markus Läll
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