| Subject: | Re: Using commas in POE::Preprocessor macros |
| Date: | Wed, 29 Sep 2004 17:07:45 -0400 |
| To: | "Westendorf, John" <JWestendorf [...] ea.com> |
| From: | Rocco Caputo <rcaputo [...] pobox.com> |
On Wed, Sep 29, 2004 at 12:34:34PM -0700, Westendorf, John wrote:
Show quoted text
> Mr. Caputo:
>
> Hi, my name is John Westendorf, and I am thinking of using
> POE::Preprocessor macros in my current Perl project. Is there a
> special
> meta-character or anything to allow me to input commas into a
> macro? So,
> in a simplistic example, I could have a line like
>
> {% macro "blahblah comma-meta-character blahblah" %}
>
> which would send in "blahblah , blahblah" as the first macro argument?
> Thanks!
>
> - John Westendorf
Good morning, John.
In an ideal world, the macro parser would know Perl syntax and detect
that the comma is in a literal string. Parsing Perl is terribly NOT
easy, however. It is sensible to run screaming when faced with the
need for it.
Adding to the macro syntax is interesting. Some really fantastic (but
off-topic) things can be done with that. It doesn't seem right that
strings must be modified when they're used in macro invocations,
though.
Perhaps the preprocessor could recognize different separator
characters. If the macro name is immediately followed by a valid
separator, then that's used to separate the invocation parameters.
{% macro ; "blahblah , blahblah" %} # separate with semicolon
{% macro , "blahblah , blahblah" %} # separate with comma (default)
{% macro | "blahblah , blahblah" %} # separate with pipe
That's extensible, and it doesn't put the onus of parsing Perl on
POE::Preprocessor, but it can break existing code in obscure
situations (where | is the first parameter, for example).
Backward compatibility can be preserved, though, if separators are
only permitted to contain commas:
{% macro ,, "blahblah , blahblah" %} # separate with ",,"
{% macro ,,, "blahblah , blahblah" %} # separate with ",,,"
{% macro ,,,, "blahblah , blahblah" %} # separate with ",,,,"
etc.
What do you think?
--
Rocco Caputo - http://poe.perl.org/