Re: Quick question on subroutine declaration syntax
On Tue, Oct 30, 2001 at 03:59:30PM +1100, Damian Conway wrote: (Though I *do* harbour a secret desire to resurrect - as a type specifier: sub foo (@args) - rettype Hmm... I would have expected is to come in here: sub foo (@args) is IO::Handle my $bar - int; Hmm... This, I think is very different. Now you're getting into casting, and I fear a Perl6 that has casting. Next, we'll have to start considering the various types of casting that C++ provides (static, dynamic, etc). Did you think of - as forcing the my expression to return a certain type or to say that $bar is of type int or to say that $bar is whatever it is, but will always be forced into an int when its value is taken (much like the behavior of Perl6 hash keys)? I could see each of those being useful, but I'm not sure they are all neccessary. -- Aaron Sherman [EMAIL PROTECTED] finger [EMAIL PROTECTED] for GPG info. Fingerprint: www.ajs.com/~ajs6DC1 F67A B9FB 2FBA D04C 619E FC35 5713 2676 CEAF Write your letters in the sand for the day I'll take your hand In the land that our grandchildren knew. -Queen/_'39_
Re: Quick question on subroutine declaration syntax
Aaron wrote:
sub foo (@args) - rettype
Hmm... I would have expected is to come in here:
sub foo (@args) is IO::Handle
It would have to be:
sub foo (@args) is type(IO::Handle)
or something, I think. Unless Larry decides that every class/module
name is implicitly also the name of a trait that confers that type on
a referent.
Personally I suspect he may prefer to stick with type-before-name:
my Dog $spot;
sub Dog hot {...}
rather than:
my $spot is Dog;
sub hot is Dog {...}
since using class/module names as auto-traits could lead to many unexpected
clashes in the traits namespace.
my $bar - int;
Hmm... This, I think is very different. Now you're getting into
casting, and I fear a Perl6 that has casting. Next, we'll have to
start considering the various types of casting that C++ provides
(static, dynamic, etc).
No, this is nothing to do with casting. It's merely an alternative syntax for:
my int $bar;
Did you think of - as forcing the my expression to return a certain
type or to say that $bar is of type int or to say that $bar is whatever
it is, but will always be forced into an int when its value is taken
(much like the behavior of Perl6 hash keys)?
The middle one.
The thinking is that a - would indicate what the preceding referent
was expected to evaluate to. So:
sub foo - Bar; # foo() expected to evaluate to a Bar
my $foo - Bar; # $foo expected to evaluate to a Bar
# and, indeed, restricted to aceepting
# a Bar on assignment
It's no different from:
sub Bar foo;
my Bar $foo;
except syntactically.
(And that's why it's probably a bad idea)
Damian
Re: Quick question on subroutine declaration syntax
For a typed subroutine with named parameters, is the declaration syntax
(sans property declaration) going to be:
'sub' type ident '(' paramlist ')' block
(in, say, Parse::RecDescent)? I'm thinking about how to add subroutines
to BabyPerl*, and I need to know if I'm at least right about the
placement of 'type'.
Larry hasn't said, but it's a pretty good bet it will be like that.
(Though I *do* harbour a secret desire to resurrect - as a type specifier:
sub foo (@args) - rettype
{
...
}
my $bar - int;
#etc.
;-)
Damian
