Luke Palmer <[EMAIL PROTECTED]> writes:
> This is for everyone: <<EOA4
>
> In Perl, this problem comes up most often when people say "Why do I
> have to put a semicolon after do {} or eval {} when it looks like a
> complete statement?"
>
> Well, in Perl 6, you don't, if the final curly is on a line by itself.
> That is, if you use an expression block as if it were a statement
> block, it behaves as one. The win is that these rules are consistent
> across all expression blocks, whether user-defined or built-in. Any
> expression block construct can be treated as either a statement or a
> component of an expression. Here's a block that is being treated as a
> term in an expression:
> $x = do {
> ...
> } + 1;
>
> However, if you write
> $x = do {
> ...
> }
> + 1;
> then the + will be taken erroneously as the start of a new statement.
> (So don't do that.)
>
> Note that this special rule only applies to constructs that take a
> block (that is, a closure) as their last (or only) argument. Operators
> like sort and map are unaffected. However, certain constructs that
> used to be in the statement class may become expression constructs in
> Perl 6. For instance, if we change BEGIN to an expression construct we
> can now use a BEGIN block inside an expression to force compile-time
> evaluation of a non-static expression:
> $value = BEGIN { call_me_once() } + call_me_again();
>
> On the other hand, a one-line BEGIN would then have to have a
> semicolon.
>
> EOA4
>
> 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.
--
Piers
"It is a truth universally acknowledged that a language in
possession of a rich syntax must be in need of a rewrite."
-- Jane Austen?
