[Swig-devel] MATLAB's "No Input Argument Constructor Requirement"

[Joel A. <j.a...@gm...>]

Hi,

I'm working on the MATLAB module now (will return with a status report
soon), but in the meantime I've got a style question.

In the current version of the module, MATLAB's so-called "No Input Argument
Constructor Requirement" is violated. This is a requirement that it should
be able to call a class constructor without an argument and essentially
just set default arguments:

a = Foo();

If we implement the "No Input Argument Constructor Requirement", the code
gets much cleaner and more efficient (no need to create a bunch of
temporary objects). The problem is that this syntax is now being used to
wrap the default C++ constructor.

Does it make sense to let the default constructor be called with a static
method instead (note that "default" is a keyword in C++, but not in MATLAB,
so a very suitable name):

a = Foo.default();

An alternative is to have the call to the default constructor be "lazy",
i.e. called the first time a member function is called:

a = Foo(); % <== Foo's C++ constructor not yet called
disp(a);  % <== Foo's C++ constructor will be called here

Any thoughts on this?

A mostly working of the above (with and without lazy constructor calls) can
be found at: https://github.com/jaeandersson/swig/issues/31

Joel