[GiNaC-list] type casting

[Marko Riedel]

Hi all,

I have a set of custom objects that is declared like this:


struct cindsym_is_less {
         bool operator() (const cindsymbol &lh,
                          const cindsymbol &rh) const
   { return lh.compare(rh) < 0; }
};

typedef std::set<cindsymbol, cindsym_is_less> cindsymset;

Now I want to collect all custom objects that appear in an expression 
tree into this kind of set. I tried this:

void indets_recurse(ex src, cindsymset & coll)
{
   if(is_a<add>(src) || is_a<mul>(src) || is_a<power>(src)){
     for(size_t idx = 0; idx < src.nops(); idx++)
       indets_recurse(src.op(idx), coll);
     return;
   }

   if(is_a<cindsymbol>(src)){
     coll.insert(src);
   }
}

However this will produce the error "no matching function call" because 
src is an expression and not a cindsymbol. I know that I have my kind of 
symbol because is_a<cindsymbol> returned true. How can I get at the 
symbol wrapped in the expression?

Best regards,

Marko