Tom asked how we'd deal with variadic subroutines without sacrificing
compile-time information (i.e. parameter lists).
Below I've indicated how RFC 128 would handle the cases he lists.
To recap: RFC 128 proposes that parameters may be given a C<:repeat>
attribute to make them variadic within a specified range of repetitions.
> I still almost always end up first using no protos and then employing
> extensive run-time comparisons, such as this sequence might illustrate:
>
> confess "need args" unless @_;
sub foo( $arg: repeat{1,} ) {...}
> confess "need even args" unless @_ % 2 == 0;
sub foo( %args ) {...}
> confess "keys mustn't be refs"
> if grep { ref }, @_[map { 2*$_} 0.. int($#_/2)] }
One can't express negative conditions via parameter list.
I suppose that if user-definable attributes were available one
might be able to write:
sub foo( ( $key:notref, $value) : repeat{1,} ) {...}
> confess "values must be hashrefs"
> if grep { reftype($_) ne 'HASH' }, @_[map {1+2*$_} 0.. int($#_/2)] }
sub foo ( ($key, \%hash) : repeat{1,} ) {...}
# or:
sub foo ( ($key, HASH $hashref) : repeat{1,} ) {...}
> confess "values must be Frobulants"
> if grep { $_->isa("Frobulant") }, @_[map {1+2*$_} 0.. int($#_/2)] }
sub foo ( (Frobulant $key, $value) : repeat{1,} ) {...}
> Could the prototype people please report whether Tim Bunce's issues with
> prototypes have been intentionally/adequately addressed?
I'm not a prototype person (in fact RFC 128 makes it a hanging offence
to use that confusing word in connection with parameter lists! ;-)
Could someone please recapitulate Tim's issues?
Damian
