Re: more on frp (was Re: [Caml-list] Re: Recursion on React.events)

[Aaron Bohannon <bohannon@seas.upenn.edu>]

On Wed, Dec 9, 2009 at 11:16 PM, Daniel Bünzli
<daniel.buenzli@erratique.ch> wrote:
>> Your example perfectly illustrates what makes understanding FRP hard:
>> when I type the string "programming", should I expect to get a signal
>> with a value of "programming" or "programing"?
>
> Note, you don't get any signal here, we are talking about an _event_.
> So the sequence of event occurences you will see is 'p', 'r', 'o',
> 'g', 'r', 'a', 'm', 'm', 'i', 'n', 'g'. Now if you fold over these
> occurences as I suggested to make a string signal, the sequence of
> changes in the signal you will see is "", "p", "pr", "pro", "prog",
> "progr", "progra", "program", "programm", "programmi", "programmin",
> "programming" (you could have chosen a shorter word, that was painful
> to write).

I apologize.  I read your message too quickly and thought that you
were using "last_keysym" to define "istr".  (And I chose the word
because it was part of "FRP". :)

> So the function time -> 'a option returns a value if there's an
> occurence of the event at that time (e.g. if the
> user pressed a key at that time) and None otherwise.

Yes, (I think) I did understand what the type "time -> 'a option" was
trying to represent.  It just doesn't seem a very good match for the
concept.  It would appear (from the type) that events could have
nonzero duration, but that doesn't match my intuition of events.

 - Aaron