[Haskell-cafe] makeFields without lenses

[Andrew Gibiansky]

Nicola,

Could you be looking for the OverloadedRecordFields[0] extension? This is
an extension that I *think* is slated to be in 7.10, and might do what you
want (though won't help you now).

If you declare two data types with the same field name (e.g. data A = A {
hello :: Int} and data B = B { hello :: Int }), the extension will generate
some typeclasses and type families so that you can use `hello` on both data
types.

(I haven't used this myself, but have been looking forward to it, so if
anyone wants to correct me on anything I've said please do so.)

[0] https://ghc.haskell.org/trac/ghc/wiki/Records/OverloadedRecordFields

On Sat, Oct 4, 2014 at 6:53 AM, Brandon Allbery <allbery.b at gmail.com> wrote:

> On Sat, Oct 4, 2014 at 5:57 AM, Nicola Gigante <nicola.gigante at gmail.com>
> wrote:
>
>> However, it generates lenses, which
>> at this time I don’t use in my little project.
>> I'll learn to use them well sooner or later,
>> I promise! In the meantime, is there
>> some module out there than provides a
>> template haskell function that do the
>> same thing but generating simple accessor
>> functions instead of lenses?
>>
>
> Anything that does this creates lenses. That does not mean that they all
> create Control.Lens, though; a lens is a general abstraction, not a
> trademark. The simplest version, focused solely on this use case, is
> probably the fclabels package.
>
> Note that the reason they do what you need is that they are lenses. Simple
> accessors will conflict as you described. fclabels is still useful if
> you're only interested in lenses for record field accessors, though, since
> the full lens package is rather heavyweight in that case --- and as a
> bonus, you'll be getting a head start on the more general concept, without
> getting dropped into the deep end of the pool.
>
> --
> brandon s allbery kf8nh                               sine nomine
> associates
> allbery.b at gmail.com
> ballbery at sinenomine.net
> unix, openafs, kerberos, infrastructure, xmonad
> http://sinenomine.net
>
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