How would I construct a capture literal that has both an invocant and
at least one positional argument? How do I distinguish this from a
capture literal that has no invocant and at least two positional
arguments?
Gut instinct: if the first parameter in a list is delimited from the
rest using a colon instead of a comma, treat it as the invocant;
otherwise, treat it as the first positional argument.
This would mean that the rules for capturing are as follows:
* Capturing something in scalar context: If it is a pair, it is
captured as a named argument; otherwise, it is captured as the
invocant.
* Capturing something in list context: Pairs are captured as named
arguments; the first non-pair is captured as the invocant if it is
followed by a colon, but as a positional argument otherwise; all other
non-pairs are captured as positional arguments.
So:
$x = /$a; # $$x eqv $a
$x = /:foo; # %$x eqv { foo => 1 }
$x = /($a,); # @$x eqv ( $a ); is the comma neccessary, or are the
() enough?
$x = /($a:); # $$x eqv $a
$x = /(:foo); # %$x eqv { foo => 1 }; assuming that adverbs can go
inside ().
$x = /($a, $b) # @$x eqv ($a, $b)
$x = /($a: $b) # $$x eqv $a; @$x eqv ($b)
$x = /:foo ($a: $b, $c):bar<baz> <== $d, $e <== flag => 0; # results
on next three lines:
# $$x eqv $a
# @$x eqv ($b, $c, $d, $e)
# %$x eqv { foo => 1, bar => 'baz', flag => 0 }
Note that this approach makes it impossible for a pair to end up
anywhere other than as a named argument in the capture object; while
this makes sense when the capture object is being used as a proxy
argument list, it makes less sense when it is being used as the
equivalent of perl 5's references, and thus is probably a bug.
--
Jonathan "Dataweaver" Lang
