[Opencxx-users] ptree design question

[Stefan S. <se...@sy...>]

hi there,

now that I freed my mind for some opencxx refactoring,
I'm looking more closely at the actual API(s).
I think a good start is to make the API a little more
const-correct, and generally work with as much type information
as is available at any given point.
Thusly I run into the following function:

Ptree* Nconc(Ptree* p, Ptree* q)
{
     if(p == 0)
	return q;
     else{
	Last(p)->SetCdr(q);
	return p;
     }
}

This is a merge of two ptrees into one, appending
'q' at the end of 'p'. That looks fine, until you
realize that a Ptree can be either a leaf or a non-leaf,
so the question is what the 'SetCdr' method will do to
a leaf. It can't just change the ptree's type, as that
is fixed in the C++ type.
Thus, is it a programmer mistake to call SetCdr on
a leaf ? Should the object assert its non-leaf-ness ?

Regards,
		Stefan