[Python-Dev] A Hygienic Macro System in Python? (original) (raw)

Samuele Pedroni pedroni@inf.ethz.ch
Mon, 18 Mar 2002 22:37:56 +0100

From: Jeremy Hylton <jeremy@zope.com>

On Mon, 18 Mar 2002 16:10:40 -0500 Tom Emerson <tree@basistech.com> wrote: > I find using 'unless' makes some things more readable. To > learn the > internals of the compiler I've been adding an unless > statement to > Python, but one shouldn't need to do this in order to add > useful > constructions like this.

Funny you should pick this example! I have been struggling with a collection of C code where the author used an UNLESS() macro. I find it obscures the program logic significantly. In part, I'm sure it's because I don't use it in any of my own C code, so it's an oddball control flow constructs to my eyes. I'm not sure that I'd like to see Python programmers acquire to many ways to spell if :-).

You're right, but even some Common Lispers would find adding sligthly different flavors of control structures, a contrived use of macros.

The point of macros is to add mini-languages such that you're main language is embedded in them. The macros of CL GUI systems are examples of that, or templating macros, and some resource handling macros.

Anyway I have toyed myself with the idea of adding macros to Python, but the conclusion is that macros do not fit in Python's ecology, or at least that you should design them from scratch trying radical new ideas. Python is not a Lisp-like language, it is probably more like Smalltalk, that means that anonymous blocks would be more natural (probably still not natural enough).

regards.