Barry Margolin <email@example.com> wrote:
| firstname.lastname@example.org (Rob Warnock) wrote:
| > Actually, this is *NOT* true!! You still need to recompile the code
| > to get the effect of any changes in the functional abstraction behind
| > the macro, since the macro (and hence the function behind it) is only
| > called during the macro-expansion phase of compilation, and is *not*
| > called at runtime! See the following for the official verbiage: ...
| It depends on how the macro is written. It's possible to design some
| macros so that they simply expand into a call to a function, and that
| function can be redefined at run time.
| I remember that many macros in the Symbolics table and presentation
| system were written something like this:
| (defmacro with-table ((stream &rest options) &body body)
| #'(lambda (,stream) ,@body)
| The macro is so trivial that it virtually never needs to be redefined.
| All the real work takes place in the function WITH-TABLE-INTERNAL, which
| can be redefined on the fly.
Sure, many "WITH"-style macros are of this style, and I've written
plenty of those myself. One set in particular was for wrapping a
"container" HTML web page around some locally-specified content.
E.g., a call to:
...[some HTOUT or CL-WHO code]...)
(normal-results-page (http-request-stream *http-request*)
(with-html-output (s s t)
...[some HTOUT or CL-WHO code]...)))
Clearly one could change the layout of the header/footer/sidebars of
such pages by redefining the NORMAL-RESULTS-PAGE *without* recompling
ot reloading any code containing uses of WITH-NORMAL-RESULTS-PAGE.
So my comment [to which you replied] was overly general. Mea culpa.
But I was mainly trying to warn about those macros that do source
code *rewriting*, for which the "underlying function" is the rewriting
algorithm itself, and which are usually of the form:
(defmacro my-macro (macro-args...)
or possibly with some very simple rearranging of the MACRO-ARGS before
calling the expansion function.
Those macros do indeed require that any binding forms calling them
be recompiled [or, for those interpreters that always do at least
ANSI CL "minimal compilation", reloaded] when the expansion function
Rob Warnock <email@example.com>
627 26th Avenue <URL:http://rpw3.org/>
San Mateo, CA 94403 (650)572-2607