Backquote macro in LFE

[oubiwann]

This is from an email that Robert sent, and it's a great idea:

I was looking through some of the examples you refer to in the LFE page when I remembered that LFEs backquote macro even works with tuples . So you can use a tuple "pattern" which expands into code to build a tuple. For example:

`#(ok ,reply) ==> (tuple 'ok reply))

With that you could write the callbacks to the ping_pong server as:

(defun init (args)
  `#(ok ,(make-state pings 0)))

(defun handle_call (req from state)
  (let* ((new-count (+ (state-pings state) 1))
         (new-state (set-state-pings state new-count)))
    `#(reply #(pong ,new-count) ,new-state)))

It of course also works in patterns. This is clearer and more concise for those who know about it but I don't think that this is something to drop on the poor unsuspecting reader from the beginning, but a section on the backquote macro would be good to have somewhere.

[oubiwann]

There was a recent email that went out to the list that ended up being a bit of a tutorial along these lines:

• https://groups.google.com/d/msg/lisp-flavoured-erlang/WajwPK4TbX0/QNdRL6Jgn14J

That might make a good starting point...

[oubiwann]

@rvirding has done some good work on this for the "official LFE tutorial" here:

• https://github.com/lfe/tutorial

The published tutorial is currently available here:

• https://lfe.gitbooks.io/tutorial/content/

The section on macros with info on the backquote is here:

• https://lfe.gitbooks.io/tutorial/content/macros/backquote.html