Python syntax in Lisp and Scheme

[Greg Ewing (using news.cis.dfn.de)]

Daniel P. M. Silva wrote:

> Haven't some people implemented an entire class system as one huge macro?

YES! Been there, done that -- about 3 or 4 times, actually.
I went through a bit of a phase where writing OO implementations
for Scheme was one of my principal hobbies. :-)

By the way, Scheme was my Favourite Cool Language for quite
a while. Then I discovered Python, and while I still appreciate
all the things about Scheme that I appreciated then, I wouldn't
want to go back to using it on a regular basis now. So it's not
a given that any person who likes Scheme must inevitably dislike
Python!

I do "get" macros, and I appreciate having them available in
languages like Scheme, where they seem to fit naturally. But
I can't say I've missed them in Python, probably because Python
provides enough facilities of its own for constructing kinds of
mini-languages (keyword arguments, operator overloading,
iterators, etc.) to satisfy my needs without having to resort
to macros.

And I do regard macros as something that one "resorts" to, for
all the reasons discussed here, plus another fairly major one
that nobody has mentioned: Unless both the macro system and
the macros written in it are *extremely* well designed, error
reporting in the presence of macros of any complexity tends to
be abysmal, because errors get reported in terms of the expansion
of the macro rather than what the programmer originally wrote.

ALL macro systems of any kind that I have ever used have suffered
from this - cpp, C++ templates, Lisp/Scheme macros, TeX,
you name it. I'd hate to see Python grow the same problems.

-- 
Greg Ewing, Computer Science Dept,
University of Canterbury,	
Christchurch, New Zealand
http://www.cosc.canterbury.ac.nz/~greg