> Luke Palmer wrote:
> > [quote from A4]
> > To me, this looks like it has answers to all these questions.
>
> Up to a point. Look at the discussion of given/when in the same
> Apocalypse. Here's some example code from A4:
>
>
> given $! {
> when Error::Overflow { ... }
> when Error::Type { ... }
> when Error::ENOTTY { ... }
> when /divide by 0/ { ... }
> ...
> }
>
> Look, closing braces, ending statements, not on a line by
> themselves. There's code like this all through the apocalypse and its
> associated Exegesis, so it looks to me like C<< rx/\} \s* \n/ >> is
> the regex for 'end of statement'. Either that or we're back with a
> pile of special cases, which I thought the Apocalypse was supposed to
> be eliminating.
That's because C<when>s are statements. Statements don't need to be
terminated. In C (or even Perl 5) you don't need to write:
if (a < b) { foo(); };
That's because the grammar says that conditionals (and loops) are
statements all by themselves, because this doesn't make sense:
1 + if (a < b) { foo(); } / 2;
But in Perl 6, things are moving around. Perl 6 needs the ability for
users to program such interfaces with subs, which I<are> expressions. So,
according to Damian, if a sub's last argument is a closure, it can (but
not necessarily will) act like a statement rather than an expression.
>From what I understand of his message, this has nothing to do with
whitespace.
I don't know the exact semantics, if they are what I think they are, then
I disagree.
sub cond_if ($condition, &code) {...} # returns something
cond_if ($x < $y) { $y }
for @a; @b; @c; # ...
This requires infinite lookahead to parse. Nobody likes infinite
lookahead grammars.
Personally, I liked the A4 decision the best ('}' on a line by itself),
and I think otherwise there's too many ambiguities like this one.
However, if an elegant solution has been (or is going to be) found, I'm
all ears.
Luke
