Re: [Maxima-discuss] How to make buildq evaluate its first argument - please help

[Stavros M. <mac...@al...>]

See Technical Issues of Separation in Function Cells and Value
Cells<http://www.nhplace.com/kent/Papers/Technical-Issues.html> (often
called "Lisp 1 vs. Lisp 2") by R.P. Gabriel for a discussion of the issues
in Lisp. Maxima, with its "variables without values represent themselves"
policy, adds another twist to the story.

In short, this is not a "bug", but a design choice, and whether you are
surprised by it depends on what you're familiar with....

Personally, I would support the syntax (f)(x) to indicate that the 'f' is
to be evaluated. This doesn't currently work, but i(f)(x), where i(q):=q,
does.

              -s

On Sun, Apr 20, 2014 at 6:07 AM, Helmut Jarausch <
jar...@ig...> wrote:

> On 04/19/2014 09:04:06 PM, Barton Willis wrote:
> > Maybe your function works perfectly. But consider:
> >
> > (%i1) gen_rhs(Ex,Vars)::= block([n:length(Ex),m:length(Vars)],
> >     Exs:subst(makelist(Vars[i]=y[i,1],i,m),Ex),print(Exs),
> >     MList:ev(makelist(makelist(Exs[i]),i,m)),print(MList),
> >     buildq([MList],lambda([t,y],matrix(splice(MList)))))$
> >
> > (%i2) george : gen_rhs([sin(a+b),cos(a*b)],[a,b])$
> > [sin(y[2,1]+y[1,1]),cos(y[1,1]*y[2,1])]
> > [[sin(y[2,1]+y[1,1])],[cos(y[1,1]*y[2,1])]]
> >
> > (%i3) george(5,z);
> > (%o3) matrix([sin(z[2,1]+z[1,1])],[cos(z[1,1]*z[2,1])])
> >
> > (%i4) y[2,7] : 42$
> >
> > (%i5) george(5,z);
> > (%o5) matrix([sin(y[2,1]+y[1,1])],[cos(y[1,1]*y[2,1])])
> >
> > Are you certain this is what you want?
> >
>
> Of course not, but I am helplessly exposed to this
> sickness of Maxima. Similarly I have to call
> apply(rhs,[x,y]) instead of just rhs(x,y) if rhs
> comes from the parameter list of the function where this call occurs.
> This means I cannot work with vector-valued functions
> except when using this ugly hack mentioned by Robert.
>
> In comparison to many other languages I have worked with
> Maxima is just broken in this respect.
> It violates the principle of least surprise.
>
> Since the assignment  y[2,7]:42  might occur anywhere, far away
> from that call  george(5,z), it's very hard to debug programs
> in Maxima.
>
> Thanks for this heads up, it's a really bad surprise.
>
> Perhaps, I should have a close look at Fricas and Yacas before
> I continue struggling with Maxima.
>
> That's really sad news,
> Helmut
>
>
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