On Fri, Jan 13, 2006 at 11:42:13PM +0000, Luke Palmer wrote:
: On 1/13/06, Dave Whipp <[EMAIL PROTECTED]> wrote:
: > What happens if I simply abandon the attempt at anonymous MMD and use a
: > named multi-sub, instead:
: >
: > {
: > my multi sub process_arg("-f", Str $f is rw) {
: > $f .= absolute_filename
: > }
: > my multi sub process_arg("--quux", Str arg1, Str arg2) { ... }
: > ...
: > my multi sub process_arg(Str _) {} # skip unrecognised args
: >
: > for @*ARGV: &process_arg;
: > }
:
: Oh, that's a clever way to process arguments. A module could probably
: turn that into a nice declarative option parsing library.
:
: Unfortuately, it the form you've written above, that doesn't work.
: That's because process_arg does not have a well-defined arity, so
: "for" doesn't know how many elements to pull of the list each time.
: In order to do that correctly, there would have to be some very fine
: communication between for and the signature pattern matcher.
:
: I could definitely see a library doing this though:
:
: getopts @*ARGV,
: -> '-f', Str $f is rw {...},
: -> '--quux', Str $arg1, Str $arg2 {...},
: -> $ { }; # ignore
:
: It is likely doable without any magic too wicked, too.
That doesn't seem sufficiently general. I'd rather see some context
that can apply a signature to the head of a list and treat the
"unslurped" part as unmatched. Maybe a "for" loop could be taught
to supply such a context, or a "when". Or maybe it's just the result
of embedding a sig inside a rule, or of matching a sig using ~~.
Basically, we just have to find a way to treat the sig as a pattern
that isn't anchored at the end.
Larry
