[Fluxus] Newbie Fluxus Questions

[Dave Griffiths]

On Sat, 2007-10-13 at 17:46 +0100, Iain Sharp wrote:
> All,
> 
> So I've just got Fluxus running on Ubuntu (see previous email). Quite
> excited to explore the language and the graphics capabilities.
> 
> A few questions though:
> 
> 1) How to get Fluxus v0.13 working with the DrScheme editor? Based on
> the email on this list I tried just putting 
> (require drfluxus)
> at the start of the script, but it generated the error
> "require: unknown module: drfluxus"
> Is there a path or something that needs updating perhaps?
> 
> BTW the web site needs an update on this.

I haven't quite finished this part yet, it's a hack atm, to be brutally
honest :) - if you just load examples/drflux.ss into drscheme, it should
open a window and run the fluxus script at the bottom.

I'm using a modified version of drflux.ss a lot to develop other scripts
with at the moment, and it seems to work well, but I need to figure out
the right approach to use in installing this file centrally. 

> 2) Is there a "right" way in Fluxus/Scheme to do things like build
> filters with a damping impact? My first thought is just to use a
> global variable to hold the past value of the filter, but if I was
> going to do this I might just as well be working in Basic.
> 
> I suppose I am still trying to get my head around what it is and isn't
> possible to do in a stateless way and how to handle state info when I
> do need it.

I'm not sure how you'd represent a filter in a pure functional way, as
by definition it needs a state, there are bigger Scheme brains on this
list who may be able to answer this better than I can (I'm still
learning Scheme).

I've experimented with representing state in various ways, and Scheme
doesn't prevent this, it actually gives you a lot of different ways to
do it (as it's not a 'pure' functional language). 

I'm currently using the class system in PLT, which I recommend, but
first (to see how its done 'under the hood' using closures) see:
http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-20.html#%_sec_3.1.1


> 3) I don't ever see myself getting used to Scheme's syntax for writing
> arithmetic expressions. Is there such a thing as a kludge function
> that does a "never mind all this functional programing, just evalute
> this algebraic expression" thing?

No - the thing that makes scheme work is this syntax, and it needs to be
wrestled with to make it worth learning. The irony is that it is much
simpler to read for algebra as there is no ambiguity of precedence etc,
when you get over the shock it starts to read much clearer (in my
experience anyway). 

> 4) On my laptop (Intel integrated graphics) Fluxus core-dumps randomly
> quite often. On my desktop (Nvidia graphics) it seems OK so far. Any
> thoughts on this?

Could you run fluxus with gdb, when it crashes type bt and post the
details here? It's likely that driver has problems with something fluxus
is doing which is accepted on other drivers - I need help to get these
things fixed :)

> 5) Is it possible to get the help text as an archive so I can browse
> it off-line?

Good idea - I'll get something sorted asap. 

> 6) Would I be right in thinking that the "built" objects are preferred
> to the "drawn" objects for doing anything non-trivial? Any
> restrictions on mixing "built" and "drawn" in the same environment?

'built' primitives are faster than 'drawn', and can be used to do much
more complicated things. In some circumstances 'drawn' primitives are
still really handy, but they are mainly useful for the kind of standard
recursive graphics type stuff.

> 7) Any pointers on how to use the physics package? I don't really know
> how to get started there.

There are some examples included which are probably the best place to
start. I'd recommend reading the ODE manual which explains things better
than I could - the principles, and types of joints etc. Otherwise, ask
more questions here :)

cheers,

dave