[PURRS-devel] Feature request: clearing lsts

[Roberto Bagnara]

I did not find in the documentation a way to erase all
the elements of an lst.  More formally, what is needed
is the functionality provided by, e.g.,

void
clear(GiNaC::lst& l) {
  for (unsigned n = l.nops(); n-- > 0; )
    l.remove_first();
  assert(l.nops() == 0);
}

Something like that turns out to be very useful in several
situations.  For an example, consider the following:

    if (match(e, pattern_1, substitution))
      ...
    else if (clear(substitution), match(e, pattern_2, substitution))
      ...
    else if (clear(substitution), match(e, pattern_3, substitution))
      ...

Please, consider the addition of such a method to GiNaC::lst.
You may not want to call it clear() though, as this is perhaps too
STL-ish (someone may be induced to think that lst is an STL container
and we do not want that ;-)
All the best

     Roberto

-- 
Prof. Roberto Bagnara
Computer Science Group
Department of Mathematics, University of Parma, Italy
http://www.cs.unipr.it/~bagnara/
mailto:bagnara at cs.unipr.it