I wonder whether it would be possible to make these special "one of
several" macros look a little more like the regular syntax. After all,
it's basically just an OR-op that the caller can hook into to specify
which alternative to choose.
Consider the case when there's just a simple alternative between two
modules, Email::Foo and Email::Bar. In the current proposal, it would
require three macros:
def foo = Email::Foo
def bar = Email::Bar
def foo_or_bar := [ :foo :bar ]
When really, we might rather it looked like a real OR-op:
choice foo_or_bar = Email::Foo (foo) || Email::Bar (bar)
For the more complicated cases, one might still prefer a macro for each
piece, in which case the 'name' of each alternative could default to
the name of the macro:
def mysql = DBD::mysql && DateTime::Format::mysql
def pg = DBD::pg && DateTime::Format::pg
choice db = {mysql} || {pg}
# the above is shorthand for: choice db = {mysql} (mysql) || {pg}
(pg)
-Ken
On Oct 16, 2004, at 4:42 AM, Randy W. Sims wrote:
Yeah, that still applies. It will have to be implemented differently
since we're using straight expressions. Right now, the best approach I
can think of is to allow two types of macros to be created.
1. A simple macro that can be substituded into the tree.
eg. def mysql = DBD::mysql && DateTime::Format::mysql
2. A special macro that represents a set of alternative options.
eg. def db := [ :mysql :pg ]
Option 2 would enable commandline options of the form: --use-mysql &&
--use-pg (or similar)
or something like that. I'm not sure I really like it. It's much more
complicated to implement this way.
A complete expression might look something like:
requires => q[
def mysql = DBD::mysql && DateTime::Format::mysql
def pg = DBD::pg && DateTime::Format::pg
def db := [ :mysql :pg ]
DateTime && {db} && Other::Stuff
];
Details subject to change...
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