Mark Stosberg wrote:
Sometimes I use 'given' blocks to set a value. To save repeating myself
on the right hand side of the given block, I found I kept want to do this:
my $foo = given { }
...and have whatever value that was returned from when {} or default {}
populate $foo.
Isn't it still the case that the last expression evaluated within a
closure is returned by the closure? And isn't a given block just a
fancy kind of closure?
The question is whether or not a code block can be used where the
parser expects an expression; for instance, could one say:
my $foo = if condition {"BAR"} else {"BAZ"};
?
I'm no expert, but it occurs to me that allowing this could be a
parsing nightmare.
ISTR a programming construct along the lines of "eval" that is
effectively shorthand for "sub { ... }()".
It turns out pugs already allow this, through the trick of wrapping the
given block in an anonymoose sub...which is then immediately executed:
my $rm = sub { given $rm_param {
when Code { $rm_param(self) }
when Hash { %rm_param<run_mode> }
default { self.query.param($rm_param) }
}}();
Not only do you get implicit matching on the left side, you get implicit
return values on the right!
I'd just like to be able to clean that up a little to:
my $rm = given $rm_param {
when Code { $rm_param(self) }
when Hash { %rm_param<run_mode> }
default { self.query.param($rm_param) }
};
So what happens if you forget to include a default in the given?
--
Jonathan "Dataweaver" Lang
