constructor matrix(void), should it exist?

[Jari Häkkinen]

See also #53 and #169

Should this constructor exist? What is the idea of having it? If one creates a matrix as "matrix m;" there is only one way to check if it is valid. Check whether m.gsl_matrix_p() is NULL or not. Is this well designed?

Peter sees no point in having an empty matrix (vector).

Peter, as spokesman of Markus, one point of having the the void constructor is to send the object into functions (in C-style)

Markus says, well Peter himself is inventing functions like matrix::nan(matrix&) which is a case where one typically needs to use the void constructor first before calling nan.

[Peter]

see ticket #53

[Jari Häkkinen]

It is decided that size() should check if gsl_matrix is NULL, zero is returned.

[Peter]

(In [732]) fixes #42