Re: Workings of UNIVERSAL::can

[Somni]

The algorithm is a simple symbol table search in method resolution order.

If the method is not in the symbol table (perhaps it's loaded with AUTOLOAD, or otherwise loaded after the ->can call) it won't be found. If it's loaded via AUTOLOAD, the module itself will need to overload can so it can answer effectively for those functions; this is somewhat tricky to get right, as you need to allow the search to continue further up the tree as necessary.

You mentioned later that ->can is not seeing your C++ functions. Unless these are exposed to the Perl level, they won't be in the symbol table; but then again, you shouldn't be able to call them from Perl, either, so finding them with ->can is simply wrong. If this is the case, you'll need to elaborate more as to what's going on.

[Anonymous Monk]

The algorithm is a simple symbol table search in method resolution order.

Hi :D

Actually :) Method resolution order is not an algorithm (or an actual order) or any more than symbol table search is an algorithm.

Or put another way, a sort-algorithm is not an actual algorithm, but a bubble-sort-algorithm is an sort-algorithm; is an algorithm.

Perl's default method-resolution-order, algorithm , is a linear-depth-first-search.

You can change that in modern perls with the mro pragma to C3 linearization

[Somni]

The fact that mro is changeable is why I said method resolution order, and not a specific order.

Taken individually, each of the items is not an algorithm. Taken together (symbol table search in method resolution order), it is an algorithm, though ill-specified due to the variable of which mro is in effect.

[Anonymous Monk]

Taken individually, each of the items is not an algorithm. Taken together (symbol table search in method resolution order), it is an algorithm, though ill-specified due to the variable of which mro is in effect.

No, taken together, it is still not an algorithm. An algorithm is well-defined by definition.

Also, its just repeating the question back at the original poster. The answer might work for "how do I print $foo?" (well, you print $foo;), but not here.