[GiNaC-list] var list

[Ralf Stephan]

This must be a faq:
Is there a function that returns a lst of all variables in an ex?
Or, what's wrong with the following (which leaves symbols empty)?


class CollectSymbols_Visitor
 : public visitor,
   public symbol::visitor
{
public:
  lst symbols;
  
  CollectSymbols_Visitor() {}
  
  void visit (const symbol& x)
  {
		for (lst::const_iterator i = symbols.begin(); i != symbols.end(); i++)
			if (*i == x)
				return;
		symbols.append(x);
  }
};

int main()
{
  symbol x("x");

  ex e = x - 2;
	CollectSymbols_Visitor collector;
	e.accept (collector);
	const lst& sym = collector.symbols;

	cout << sym << endl;

}