Common Lisp Macros Without Parantheses and Unusual Call Syntax

Question

I am wondering how one writes macros in Common Lisp that allow him to part with Lisp forms in calls to the former.

For instance, suppose I have the following macro:

(defmacro define-route ((app uri method) &body body) `(setf (ningle:route ,app ,uri :method ,method) ,@body))

A call to it would look something like this:

(define-route (*app* "/" :GET) (print "Welcome to ningle using GET!"))

What if one wanted to write a macro that could be called like this:

@route(*app*, "/", :GET)

or like this:

route: *app*, "/", :GET

Is this possible? I have seen the @route syntax somewhere before but am not sure how to implement it, nor do I remember what it was called to look it up again.

Lisp macros can't do that. But if you want to develop a new programming language syntax, you can write a parser for it. If you want to do basic extensions to s-expressions, then google for 'reader macros'. — Rainer Joswig
– Rainer Joswig, Commented Apr 5, 2018 at 7:30

Ehvince · Accepted Answer · 2018-04-05 13:04:15Z

We encounter this decorator syntax (or annotations in CL) in the Caveman or Lucerne web frameworks:

@route GET "/" (defun index () (render #P"index.tmpl"))

I doubt you can do route: *app*, "/", :GET.

cl-annot is a general annotation library for CL.

It is a reader macro, more examples here: http://lisp-lang.org/wiki/article/reader-macros

ps: Snooze, by the author of Sly (and yasnippet), is a web frameworks that treats routes as usual functions, thus route parameters as usual function arguments. It also has built-in reporting of errors (in browser, in the debugger, with a custom 404 page). I liked it better than the two mentioned. No big experience with either of them.

@MadPhysicist did I already tell you about Snooze ? Just updated my answer. In my little experience it was easier and more consistant than caveman or ningle.
No, I have never heard of Snooze until now. Will check it out!

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