On 13.08.2014 15:42, Heinrich Apfelmus wrote:
Validation is mainly a question of *how* to present feedback about invalid data to the user -- for instance by making invalid data impossible to enter, or by showing errors in red and retaining the last correct value, etc.
I don't even know how to capture validation rules in such a way that they were easy to use from the GUI layer. I suspect if they were captured well, whatever well might mean in this context, a functioning GUI could be autogenerated from those rules. And I don't understand FRP code. I could however understand Eduardo's client side formlets almost immediately. Not now they work below, how to use them.
Still, even for the more narrow problem of forms and input validation, I don't see how you arrive at your claim that "Haskell is however not great for GUIs". This seems like a problem that can be solved with a traditional DSL approach, and I would be surprised if Haskell were unsuitable as a host language, contrary to what your claim seems to imply. Whether DSLs along these lines are already available is another question. Alberto mentioned one, another one would be [1].
Oh, please. Haskell is great for parsing, because you can build a parser with e.g. parsec, attoparsec, uuparse, trifeca, in no time. Even I can do it. Haskell is great for concurrency, because it has lightweight threads, STM, and a fabulous book about it. Haskell is great for GUIs, because.... how about you finish this statement, I don't know how to. -- Kind reagrds, Wojtek Narczynski