SDR should return itself (C++)

[ctrl-z-9000-times]

Currently in python, the SDR class returns itself after most method calls. This allows several method calls to be chained onto one line. For example:

X = SDR( 1000 ).randomize( .02 )

Currently in C++, the SDR class returns void after most method calls. It should be simple to change the SDR class to return SDR *this and allow clever one liners like:

X = (new SDR({ 1000 }))->randomize( .02 )