making for-loops more general. Was: Re: New version of makelist

-----maxima-bounces at math.utexas.edu wrote: -----

>I?notice?that?the?for-loop?stuff?does?NOT?permit?the?index?to?be?(say)???
>x[k].?Is?this?really useful???

This prohibition is good. It's tempting to use x[1], x[k], ... as
ordinary variable names, but if the implicitly defined hashed array x
is assigned a value, the code might misbehave. Also, the Maxima translator
generates bogus code for hashed arrays that are declared local (at the
least the translator alerts the user)

 (%i1) bob() := block([x], local(x), x[1] : 42)$

 (%i2) translate(bob)$

 Local does not work well in translated code.
 Try to use value cell and the Use_fast_arrays:true              
 if this is for arrays.  For functions, local definitions are
 not advised so use lambda expression

 (%i3) x[1];
 (%o3) x[1]

 (%i4) bob();
 (%o4) 42

 (%i5) x[1];
 (%o5) 42

And explain this:

 (%i1) (a : b, b : c, c : d)$

 (%i2) [a,a[1]];
 (%o2) [b,d[1]]