[Haskell-cafe] What Haskell Records Need

[Thiago Negri]

I'm new to Haskell, but I do like your idea.

I prefer this as a built-in feature because it will create a standard
way of doing this, making the question "wich package should I use to
get mutatos? lens-foo, lens-bar, monad-lens, lens-lens-foo-bar, ...?"
simply go away.

So, yes, I up-vote your idea to write an official proposal.

Thiago.

2012/8/2 Jonathan Geddes <geddes.jonathan at gmail.com>:
>
> Richard O'Keefe Said:
>>> Ouch! And that's not even very deeply nested.
>>> Imagine 4 or 5 levels deep. It really makes
>>> Haskell feel clunky next to `a.b.c.d = val`
>>> that you see in other languages.
>>
>>I was taught that this kind of thing violates the Law of Demeter
>>and that an object should not be mutating the parts of an
>>acquaintance's parts, but should ask the acquaintance to do so.
>>I'd say that a.b.c.d = val is at the very least a sign that
>>some encapsulation did not happen.
>
> Absolutely! But in Haskell how do you do the
> asking? I guess that's what I'm proposing is
> a built in way of doing just that! I'm
> shooting for as-easy-as the built in getters.
>
> Erik Hesselink said:
>>Isn't this exactly the problem solved by all the lens packages?
>
> Yes it is. I think the existence of these
> packages along with all the proposals to
> change records is an indication that
> something is missing from the language as a
> whole. What I'm proposing is that the
> language give you something that is
> lightweight and easy to use to address this
> issue. You can still use lenses on top of all
> of this.
>
>> makeLens myField myField'
>
> If I remember correctly, one of the problems
> with lenses is that they cannot support
> polymorphic updates (updates which change a
> type variable of the data). SEC functions, on
> the other hand support polymorphic updates.
>
> --Jonathan
>
> On Thu, Aug 2, 2012 at 4:48 AM, Andrew Butterfield
> <Andrew.Butterfield at scss.tcd.ie> wrote:
>>
>> Ah yes - the joy of Haskell
>>
>> It so easy to roll your own, rather than search to find someone else's
>> (better/more elegant) solution...   :-)
>>
>>
>> On 2 Aug 2012, at 11:41, Erik Hesselink wrote:
>>
>> > On Thu, Aug 2, 2012 at 12:30 PM, Andrew Butterfield
>> > <Andrew.Butterfield at scss.tcd.ie> wrote:
>> >>
>> >> On 2 Aug 2012, at 09:25, Erik Hesselink wrote:
>> >>
>> >>> Isn't this exactly the problem solved by all the lens packages?
>> >>> Current popular ones are fclabels [0] and data-lens [1].
>> >>>
>> >>> [0] http://hackage.haskell.org/package/fclabels
>> >>> [1] http://hackage.haskell.org/package/data-lens
>> >>
>> >> Not sure what all of these do, but I have a simple solution I use
>> >> in my work:
>> >
>> > They do exactly that. They create 'lenses' which are
>> > getters/setters/modifiers combined, and allow you to compose these to
>> > get/set/modify deep inside nested data types. Look at the examples in
>> > the fclabels documentation [2] for more details.
>> >
>> > [2]
>> > http://hackage.haskell.org/packages/archive/fclabels/1.1.4/doc/html/Data-Label.html
>>
>> --------------------------------------------------------------------
>> Andrew Butterfield     Tel: +353-1-896-2517     Fax: +353-1-677-2204
>> Lero at TCD, Head of Foundations & Methods Research Group
>> Director of Teaching and Learning - Undergraduate,
>> School of Computer Science and Statistics,
>> Room G.39, O'Reilly Institute, Trinity College, University of Dublin
>>                           http://www.scss.tcd.ie/Andrew.Butterfield/
>> --------------------------------------------------------------------
>>
>>
>> _______________________________________________
>> Haskell-Cafe mailing list
>> Haskell-Cafe at haskell.org
>> http://www.haskell.org/mailman/listinfo/haskell-cafe
>
>
>
> _______________________________________________
> Haskell-Cafe mailing list
> Haskell-Cafe at haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe
>