Handling subscripted expressions WAS: Simplifying by replacing expressions?

You don't actually need to delve into Lisp -- Maxima provides all the
necessary primitives.

However, subscripting in Maxima is idiosyncratic.  In particular,
part/inpart do not allow you to tell the difference between f(x) and
f[x] -- you need to use the subvarp predicate, and then rebuild usinjg
arraymake instead of funmake.

By the way, be sure to use funmake/arraymake and not apply/arrayapply.

The following code walks an expression and reconstructs it:

copy_expr(e) :=
  if atom(e) then e
    else
      (if subvarp(e) then 'arraymake else 'funmake)
        (copy_expr(part(e,0)),map(copy_expr,args(e)));

Tests:
  copy_expr(1);
  copy_expr(x);
  copy_expr(x^2+1/y);
  copy_expr(f[i]+g[i](x));
  copy_expr((a+b)[i]);
  copy_expr('([a,b,c][i]));

Let me know if you have any problems with this.

                 -s