how to pass the name of a variable as argument?

Actually, common lisps must also support dynamic scope, but you have to
declare those
names to be "special".  I suppose Maxima could do the same.  



> -----Original Message-----
> From: Oliver Kullmann [mailto:O.Kullmann at swansea.ac.uk] 
> Sent: Saturday, May 03, 2008 12:36 AM
> To: R Fateman
> Cc: maxima at math.utexas.edu
> Subject: Re: [Maxima] how to pass the name of a variable as argument?
> 
> Ha, in my library I use quite a bit of dynamic scoping!
> And since this is the only means in Maxima/Lisp, as
> far as I see, to got some form of polymorphic behaviour,
> it seems also necessary to me.
> 
> Only due to dynamic scoping you can make good use of "global"
> variables, since when calling a function you can make
> it act similar to some form of inheritance.
> 
> So dynamic scoping seems *essential* to me:
> Back in the old days polymorphism wasn't much
> of an issue, and structured programming was
> the king, so I don't think those "good old
> arguments" have such much relevance anymore.
> Maxima without dynamic binding looks crippled to me.
> 
> Oliver
> 
> 
> On Fri, May 02, 2008 at 01:44:23PM -0700, R Fateman wrote:
> > Robert Dodier wrote:
> > > On Thu, May 1, 2008 at 6:14 PM, Oliver Kullmann
> > > <O.Kullmann at swansea.ac.uk> wrote:
> > >
> > >   
> > >>  Since global variables should be avoided,
> > >>     
> > >
> > > Bear in mind that, in Maxima, effectively ALL variables 
> are global variables,
> > > or, more precisely, global variables and local variables 
> act the same.
> > > All variables have dynamic scope, not lexical scope.
> > >
> > > As you doubtless know, dynamic scope can lead to subtle 
> misbehavior.
> > > A lexically-scoped user language could be very useful.
> > > Instead of revising the existing Maxima language, at this 
> point I think
> > > the easiest way to get lexical scope is to run a 
> different language
> > > on top of Lisp. One possibility is Python; there is a CL 
> implementation
> > > of Python name CLPython. The developer is talking about porting it
> > > to SBCL.
> > >   
> >  <snip>
> > The Macsyma/ Maxima language is modelled on Algol 60, a 
> language which 
> > was sort of misunderstood when implemented at MIT.
> > The mistake was to adopt the dynamic scope of Maclisp in 
> the Macsyma 
> > language.  The use of dynamic scope in lisp 1.5, according to John 
> > McCarthy, was a mistake.  Subsequent experiments at MIT in 
> lisp-like 
> > languages got the Algol 60 lexical scope "right".  It 
> resulted in  Scheme.
> > 
> > Now if you want to adopt lexical scope in Maxima,  I think 
> it is not 
> > necessary to change the syntax or language at all, just the 
> implementation.
> > (I am assuming that definition of procedures within 
> procedures would be 
> > handled properly...)
> > That is, the surface syntax would look identical. There is 
> no need to 
> > adopt python, or java or C# or ....
> > 
> > Would this break existing programs?  Maybe some.  It is my 
> understanding 
> > that Maple, between versions 9 and 10 (I think) changed the 
> language 
> > implementation from dynamic to lexical scope.  And there is 
> way way more 
> > code in the Maple language than in Maxima top-level syntax.
> > 
> > Most programmers probably don't understand the scoping 
> issues and use 
> > only global variables or local variables, and do not nest 
> procedures.  
> > So it will not make any difference in their code.
> > 
> > There is another issue which has to do with 2-lisp vs 
> 1-lisp semantics, 
> > and whether you can have two bindings for the same name, a 
> function and 
> > a variable, or just one.
> > That is, can you do f(x):=.....  
> > and also f:3.
> > or will the second assignment over-write the first.
> > 
> > Common Lisp,  and Maxima,  is a 2-language. Scheme is  a 1-lisp.
> > 
> > Now it may be appropriate to build another front end, 
> interpreter, etc, 
> > for Maxima, based on python.  Probably not too hard.  There 
> is, for example,
> > another front end for Macsyma that used Matlab syntax. It 
> could entirely 
> > co-exist with the existing one..
> > 
> > Or the alternative could be a front end for the lexically scoped 
> > language that looks just the same,  but is subtlely different.
> > 
> > My 2 cents..
> > 
> > RJF
> > 
> > 
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