Piers Cawley writes:
: Hmm... making up some syntax on the fly. I sort of like the idea of
: being able to do
:
: class File;
: sub foreach ($file, &block) is Control {
: # 'is Control' declares this as a control sub, which, amongst
: # other things 'hides' itself from caller. (We can currently
: # do something like this already using Hooks::LexWrap type
: # tricks.
Maybe, but we'll need more explicit parsing control for other things,
so this may fall out of that.
: open my $fh, $file or die $!; POST { close $fh }
More like:
my $fh = open $file or die;
: while (<FILE>) {
: my @ret = wantarray ?? list &block() :: (scalar &block());
: given $! {
: when c::RETURN { return wantarray ?? @ret :: @ret[0] }
: }
: }
That "given $!" would have to be a CATCH, or the code would never be
executed on a control exception.
: This is, of course, dependent on $! not being set to a RETURN control
: 'exception' in the case where we just fall off the end of the block.
I'd say that's correct.
: It's also dependent on being able to get continuations from caller
: (which would be *so* cool
Hmm, might not need to go that far.
: > allow this:
: >
: > File.foreach('/usr/dict/words') { print }
:
: Sounds plausible to me.
We're not using Ruby syntax here. Any closure is a real argument with
a real formal argument name, and is called via ordinary &block(...)
syntax, not yield.
: > or would the prototype be (&file, &block)?
:
: I prefer the ($file, &block) prototype.
I don't see why it would ever be &file. It's just a string.
: > And would this:
: >
: > my $caller = caller;
: > File.foreach('/usr/dict/words') {
: > print $caller eq caller ? "ok" : "not ok"
: > }
: >
: > be ok or not ok? It has to be ok if mywhile is going to emulate a
: > while loop.
:
: In theory there's nothing to stop you writing it so that that is the
: case. I'd like it to be as simple as adding an attribute to the
: function declaration (and if it isn't that simple out of the box, it
: will almost certainly be, if not trivial, at least possible to write
: something to *make* it that simple...)
Precisely.
Larry
