[Haskell-cafe] The Good, the Bad and the GUI

[Tikhon Jelvis]

For the original question: take a look at functional reactive programming
(FRP). It takes a slightly different approach to the whole GUI problem,
but, I've found, obviates some of your issues.

You can quickly play around with FRP and HTML UIs by using threepenny-gui
and Reactive Banana. The former is a simple UI framework that lets you
create and interact with HTML in Haskell, and the latter in a nice library
for FRP. They work well together:

http://apfelmus.nfshost.com/blog/2013/08/02-reactive-banana-threepenny.html

There's a nice tutorial about FRP and Reactive Banana you can read on the
Haskell Wiki. I haven't had the chance to go through it myself, but it
looks promising.

http://www.haskell.org/haskellwiki/FRP_explanation_using_reactive-banana

If you're wondering about Haskell and UIs, I think FRP is the best place to
look—it provides the most pleasant semantics for programming UIs that I've
come across, although most of the libraries are still a bit experimental.
(Implementing the exact semantics we'd like turned out to be very
difficult!)

> The reactive solutions complicates the problem rather than to simplify
it. That means that they are not the correct paradigm.

That's a very hasty, superficial way to dismiss a whole paradigm!

FRP libraries have proven *difficult to implement*, but this does not mean
they somehow "complicate the problem". The real insight with FRP is
developing a nice semantics *for the end user* and making it simpler to
work with the libraries, at the expense of a more complex implementation.
It's a parallel to functional programming at large: we're willing to trade
complexity in GHC in return for a nicer high-level programming environment.

Formlets are an interesting concept, but they seem to be significantly more
narrow than FRP. How do formlets address continuous things like animations
or mouse movement?

Also, a lot of the examples (at least on the Haskell wiki[1]) seem pretty
amenable to FRP. How is

    chooseBool :: Form Bool
    chooseBool = enumRadio [(True, "Yes"), (False, "No")] True

significantly different from just providing a Behavior Bool in the spirit
of FRP?


On Mon, Aug 11, 2014 at 3:57 PM, Wojtek Narczyński <wojtek at power.com.pl>
wrote:

>
> On 12.08.2014 00:53, Alberto G. Corona wrote:
>
>> I think that the GUI people hace to embrace the formlet concept, used in
>> HTML interfaces sooner better than later. The GUI development has lost the
>> train by trying to interface C libraries that are decades old. The reactive
>> solutions complicates the problem rather than to simplify it. That means
>> that they are not the correct paradigm.
>>
>>  I'm mainly interested in HTML/JS GUIs. Perhaps I should have stated it
> explicitly upfront.
>
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