> Date: 20 Jan 2003 20:30:07 -0000
> From: Smylers <[EMAIL PROTECTED]>
>
> It seems that when chaining together functions, omitting C<< <~ >>
> operators gives the same result in the familiar Perl 5 standard
> function-call syntax:
>
> @foo = sort { ... } <~ map { ... } <~ grep { ... } <~ @bar;
> @foo = sort { ... } map { ... } grep { ... } @bar;
>
> Left-right pipelines make sense to me. I'm not yet sure how much I'd
> use them, but there are times when I find it a little odd to have data
> flowing 'upstream' in code, and reversing this could be nifty.
Agreed.
> However right-left pipelines don't seem to add much to the language,
> while becoming something else to have to learn and/or explain.
> (Damian's explanation of what C<< <~ >> does to code seemed
> significantly more involved than that of C<< ~> >>.)
It's simple: it's a backwards dot. The invocant goes on the right
and the method and arguments go on the left.
$foo.bar($baz);
-or-
bar $foo: $baz;
is the same as:
bar $baz <~ $foo;
And you see now what this gives us. It gives us the ability to place
the invocant (almost) anywhere we want: On the left, in between, or
on the right. I think it's fortunate that we can't put it between
arguments...
> And an alternative spelling for the assignment operator[*0] doesn't
> strike me as something Perl is really missing:
>
> $msg <~ 'Hello there';
> $msg = 'Hello there';
Yeah, I didn't see much gain in this bit. But it's an expectable
generalization from ~>.
> I realize that there's a symmetry between the two operators, but that
> isn't a convincing reason for having them both. People are used to data
> flow in one direction; it seems reasonable only to have an operator when
> wanting to change this, to make it go in the opposite direction.
>
> What benefit does C<< <~ >> bring to the language?
Again, it provides not just a "null operator" between to calls, but
rather a rewrite of method call syntax. So:
map {...} <~ grep {...} <~ @boing;
is not:
map {...} grep {...} @boing;
But rather:
@boing.map({...}).grep({...});
Which will be defined to mean the same thing, but in many cases this
won't be true. Another example:
print "Starting server\n" <~ open "> $logfile";
The important thing is that it's starting the server, not that it's
writing that to the logfile.
I personally think that this could add something to readability at
times. Maybe not as much as ~>, but every once in a while.
Luke
