[Haskell-cafe] Draft chapters of "Real World Haskell" now publicly available

Wolfgang Jeltsch g9ks157k at acme.softbase.org
Thu Feb 7 06:25:24 EST 2008

Hello Peter,

an answer to an “old” e-mail (from January 25).  Sorry for not answering 

Am Freitag, 25. Januar 2008 00:23 schrieben Sie:
> Wolfgang Jeltsch wrote:
> > Indeed.  A functional approach to GUIs is nice but at the moment we don’t
> > have anything that is suitable for solving real world problems (although
> > this is being worked on).
> Could you elaborate a bit on that? What are the current obstacles to be
> solved?

Performance problems and lack of widgets are the two things that come to my 
mind immediately.  Maybe also lack of a good way of doing dynamic user 
interfaces (user interfaces with a changing set/order of widgets).

> When I looked at Yampa, I didn't really see a problem with making a GUI
> or interactive application based on it (besides maybe performance and
> space/time leaks, the latter IMO being a general problem in Haskell that
> just occurs quicker in reactive programming).

I think, performance is a big problem.  To me it seems that Yampa-based GUIs 
maybe have a performance penalty of more than just a constant factor.  Please 
have a look at the sections “Implementation and efficiency” and “Signals” 
under <http://haskell.org/haskellwiki/Talk:Grapefruit>.

> […]

> The main problem I could see is that Yampa is not really event driven in
> the imperative sense; I mean in an ideal event based system, the
> hardware triggers an interrupt when some sensor changes, and this then
> triggers other software events; only the code that is related to
> handling the event that occurred is executed. But the event that is
> handled could potentially not be needed for the current output (which
> could be considered as a programming bug...)

Not necessarily a bug.  There are events which don’t result in changes of the 
GUI, for example, mouse clicks into empty areas.

> […]

Best wishes,

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