catch instance Foldable ((, ) a)

[Andreas Abel]

Tuples are defined in the Prelude, but not used "everywhere".  The only 
uses are when a function returns several results, like in splitting 
list, quotrem etc.  These are perfectly fine uses of tuples.

Tuples are for short-lived aggregations of data.  Longer living 
aggregations deserved telling names for the sake of code comprehension. 
In our project Agda we have tons of clones of Bool, Maybe, Either, and 
(,) for the sake of giving telling names to data representations.  In 
short sight this is a "waste of programmer time and effort", but in long 
sight this is a major productivity boost.  We want to be able to read 
and maintain our code written in the 2000s still in the 2020s, and 
hopefully 2030s and 2040s.

When you want to "traverse" it is maybe time to name your tuple.

Btw. ((,) a) is more than a Traversable, it is a "Decoration":

 
https://github.com/agda/agda/blob/c5a36ee4ef4780d0c2980a4e1a04355239c42f34/src/full/Agda/Utils/Functor.hs#L46-L61

It commutes with every Functor, not just with any Applicative.

In the end it comes down what you want to produce.  For quick prototypes 
and throw-away tools it is fine to use Bool, Maybe, Either and tuples, 
but for long-living software I can only recommend to abstain.

Best,
Andreas

On 2020-05-29 16:54, Zemyla wrote:
> On Fri, May 29, 2020, 09:43 Henning Thielemann 
> <lemming at henning-thielemann.de <mailto:lemming at henning-thielemann.de>> 
> wrote:
> 
> 
>     You can also call it a beginner's problem to use tuples everywhere,
>     where
>     custom data types would be the better choice.
> 
> 
> Except the Prelude uses tuples everywhere, as do hundreds of libraries 
> based on it, and rewriting all the functions which use them for every 
> single decorated data type you plan to use is a waste of programmer time 
> and effort.
> 
> 
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