orf (a Common Lisp version of ||=)

I've recently been programming in ruby and one of the handy operators I've
been using has been ||= .

If you haven't seen it before think of it in terms of += .
So x ||= 3 is equivalent to x = x || 3.

I've found this pretty useful in a couple of cases and decided to write a
CL implementation of it. I give you ORF.



(defmacro orf (place value &environment env)
 (multiple-value-bind (vars vals store-vars writer reader)
   (get-setf-expansion place env)
 `(let* (,@(mapcar 'list vars vals)
         (,@store-vars (or ,reader ,value)))
    ,writer)))

So now (orf x 3) === (setf x (or x 3))

with the minor caveat that x will only being evaluated once.

Truly, Lisp is the Borg of programming languages.

darjeeling

This looks as if it could be quite interesting.

The ability to convert Ruby to Common Lisp (or ideally just load ruby files) should put paid to complaints about the lack of libraries in CL.

Of course it could turn out to be absolutely nothing but I'm going to keep an eye on it.