Re: How the backquote and the comma really work?

[Michael Heerdegen]

Drew Adams <drew.adams@oracle.com> writes:

> So `,foo evaluates variable foo, and `',foo evaluates foo and quotes
> the result.

Yes, that's an aspect that was missing in the mental model: backquote
works recursively, i.e. unquoting at deeper list levels is handled as
well.

> (setq titi `',foo) ; => 'bar

Whereby we don't want to conceal that the "'" is also a reader macro:
'thing -> (quote thing).

Here is the expression the reader generates for "`',foo":

  (read "`',foo") ==> (\` (quote (\, foo)))

(be sure to eval with print-quoted nil, the default).


Michael.