# [Maxima] On broken wheels and user contributed code

Richard Hennessy rich.hennessy at verizon.net
Sun May 24 14:43:31 CDT 2009

```Maybe I should have explained this better.

periodic(expr,x,a,b):=
block
(
ratsubst(a+mod(x,b-a),x,expr)
)\$

The idea is the expr is modified so it repeats it's behavior between a and b for all x an infinite number of times.  Hence the name
periodic.

Rich

----- Original Message -----
From: "Richard Hennessy" <rich.hennessy at verizon.net>
To: "dlakelan" <dlakelan at street-artists.org>; "Maxima Mailing List" <maxima at math.utexas.edu>
Sent: Friday, May 22, 2009 9:05 PM
Subject: Re: [Maxima] On broken wheels and user contributed code

Regarding pw.mac.  I had an idea a while ago of a new function called periodic

periodic(_expr,_x,_a,_b):=
block
(
ratsubst(mod(_x,(_a-_b)), _x, _expr)
)\$

It would be possible with some thinking to work out integrals of this function for many possible expr's.

Any interest?

Rich

----- Original Message -----
From: "Richard Hennessy" <rich.hennessy at verizon.net>
To: "dlakelan" <dlakelan at street-artists.org>; "Maxima Mailing List" <maxima at math.utexas.edu>
Sent: Friday, May 22, 2009 6:29 PM
Subject: Re: [Maxima] On broken wheels and user contributed code

"If I found a machine to host a monotone database
would there be interest on the part of the contributed code developers
in participating in that system?"

I think I would be interested but right now I am thinking of just doing more on my own site.  Now sure how many people are
interested in piecewise functions though.  My latest interest is extending integrate to be able to do the inverse Fourier transform
of stuff like this

(%i1) integrate(%k*((%i*%e^(-2*%i*%pi*c*t))/(2*%pi*t)-(%i*%e^(-2*%i*%pi*a*t))/(2*%pi*t))*exp(2*%pi*t*x*%i),t,minf,inf);
(%o1) k*(signum(x-a)-signum(x-c))/2

Not sure if this will work out, I am just exploring the problem.  Maybe lookup tables is the best way to do this.

Rich

----- Original Message -----
From: "dlakelan" <dlakelan at street-artists.org>
To: "Richard Hennessy" <rich.hennessy at verizon.net>; "Maxima Mailing List" <maxima at math.utexas.edu>
Sent: Friday, May 22, 2009 5:49 PM
Subject: Re: [Maxima] On broken wheels and user contributed code

Richard Hennessy wrote:
> I would like to have a forum of some kind for user contributed code,
> the list is not good for feedback. I have not received a single email
> of feedback on what I have been doing in my pw package.  That makes
> it hard to find any bugs when you are "on your own".
>
> Rich

I should say that I think your PW package sounds like it's great based
on what you've posted and examples on your website, but I have not had
any occasion where a need to use piecewise functions has arisen. So the
lurkers out here are not ignoring you entirely.

As a general suggestion, there have been some recent improvements to
version control systems which would provide a much cleaner and better
distributed version controlled contribution archive. I'm thinking for
example of "monotone" a version control system where each participant
keeps a local database that can act in a disconnected manner, but can
synchronize with other databases as changes are made.

If we set up a contributed maxima code archive, with a monotone database
being served from some computer system run by one of the contributed
code developers, and maxima contributors synchronized with it, we could
have a more flexible system for handling contributed code without
needing to give a lot of secondary developers write access to a primary
CVS archive for maxima.

Monotone went through a period several years ago where it was changing
rapidly, but recently has been very stable and speed issues have been
largely figured out. If I found a machine to host a monotone database
would there be interest on the part of the contributed code developers
in participating in that system?

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```