No macros in Python

[Lulu of the Lotus-Eaters]

Mike Meyer <mwm at mired.org> wrote previously:
|Ok.  You hand it an arbitrary set of python statements and a
|string. Those statements are executed with all output that would
|normally go to sys.stdout appended to the file. That output having
|been appended to the file is the only change in the i/o subsystem
|after the code has executed...

I'm not actually going to bother doing this, but we all realize this is
simple enough to do with a Python function.  It's not a function I
particularly need, but my earlier example demonstrated the general style
for writing the specified function.  Do one to your satisfaction, then
stick it in a library for later use.

|Macros don't change the syntax of the language any more than functions
|- or callable objects in general - do.

The expression:

    with_output_to_file('fname',['print x,y,z'])

matches the production:

    call ::= primary "(" [argument_list [","]] ")"

in <http://www.python.org/doc/current/ref/grammar.txt>

Show me which production matches:

    with_output_to_file "fname" : print x,y,z

If you cannot, your macro changes the syntax.  It's as simple as that.

|Another prettier way is:
|        val = (foo, bar)[pred]
|but it evaluates both foo and bar regardless of pred.

In other words, this is not semantically a ternary operator.  At least
not the one that C programmers are familiar with.  But that spelling
does have a certain elegance where the extra evaluation doesn't matter.

Yours, Lulu...

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