[Haskell-cafe] Tetris

[Peter Verswyvelen]

First of all Conal, I find all of your work amazingly cool. Do you have 
fan list? ;-)

Conal Elliott wrote:
> Moreover, functional programming makes it easy to have much more state 
> than imperative programming, namely state over *continuous* time.  The 
> temporally discrete time imposed by the imperative model is pretty 
> puny in comparison.  Continuous (or "resolution-independent") time has 
> the same advantages as continuous space: resource-adaptive, scalable, 
> transformable.
Yes, that's true, but isn't that also the problem with FRP? I mean, most 
of the papers I'm reading about (A)FRP indicate that no matter how nice 
it is to have the continuous time model, to get fine grained control 
over execution times and resources, one needs to fall back to the 
discrete delta-time approach? And you still need to think about where 
you have to introduce delays to avoid infinite loops? I might be wrong, 
since I don't understand everything in these papers yet ;-)

About continuous time; it is in fact, not really continuous is it, since 
floats are used to approximate time. So the longer your program runs, 
the less accurate an absolute time value will become no? Okay, if you 
use 64-bit floats, you will have to let is run a very long time :-)

Since nobody replied yet on my question about the future of (A)FRP, 
maybe I can ask it again here? What is the future for FRP? Are other 
approaches better suitable for reactive applications?

About Monadius, yes, I also think it's very nice. It is based on IMO one 
of the greatest videogames ever, Gradius (aka Nemesis). You don't want 
to know how much money I put in those Konami arcade machines ;-) But 
Monadius just mimics the imperative discrete time approach, which of 
course, does work, since 99.99% or so of the videogames on the market 
use this approach. Monadius is really easy to understand for Haskell 
newbies, and it shows that you actually can make a nice game without 
using incredibly tricky abstractions :-)  However, I found that as soon 
as I try to make my own combinators, to piece several "reactive objects" 
together, I always seem to mimic FRP, and finally AFRP.

Cheers,
Peter

Conal Elliott wrote:
> Moreover, functional programming makes it easy to have much more state 
> than imperative programming, namely state over *continuous* time.  The 
> temporally discrete time imposed by the imperative model is pretty 
> puny in comparison.  Continuous (or "resolution-independent") time has 
> the same advantages as continuous space: resource-adaptive, scalable, 
> transformable.
>
> On Nov 20, 2007 4:11 PM, Lennart Augustsson <lennart at augustsson.net 
> <mailto:lennart at augustsson.net>> wrote:
>
>     I implemented Tetris in LML long before Haskell existed.
>     It was text based, but looked good with a custom font. :)
>
>     Haskell has no problem with state, it's just explicit.
>
>       -- Lennart
>
>     On Nov 19, 2007 9:25 PM, Andrew Coppin
>     <andrewcoppin at btinternet.com <mailto:andrewcoppin at btinternet.com>>
>     wrote:
>
>         If you were going to implement Tetris in Haskell, how would
>         you do it?
>
>         (For that matter, has anybody already *done* it? It would
>         probably make
>         a nice example program...)
>
>         I'm particularly interested to know
>
>         1. How exactly would you do the graphical components? (Presumably
>         there's some deep trickery with Gtk2hs that can draw free-form
>         stuff
>         like this.)
>
>         2. How do you implement a program that is fundamentally about
>         state
>         mutation in a programming language which abhors state mutation?
>
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