> Mailing-List: contact [EMAIL PROTECTED]; run by ezmlm
> Date: Thu, 31 Oct 2002 22:36:58 -0800
> From: Michael Lazzaro <[EMAIL PROTECTED]>
> X-Accept-Language: en,pdf
> Cc: [EMAIL PROTECTED]
> X-SMTPD: qpsmtpd/0.12, http://develooper.com/code/qpsmtpd/
>
> Larry Wall wrote:
> > Please don't think of C<bit> as a boolean type. There is no boolean
> > type in Perl, only a boolean context. Or looking at it from the
> > other direction, *every* type is a boolean type.
>
> Er... dang. While I certainly agree with the concept in principle, I'm
> having a hard time sticking to it when I'm writing beginner-level docs.
> Suppose I'm declaring something like:
>
> class Appliance {
>
> has bit $.is_plugged_in;
> has bit $.is_turned_on;
> has bit $.has_ul_approval;
> }
>
> I'm declaring three attributes that are specifically always either true
> or false. They can *only* be true/false, or yes/no, or 1/0 -- they have
> no other possible values, and I want to declare them in such a way as to
> clearly enforce that behavior. C<$.is_plugged_in> is never "5" or
> "timmy" -- only true or false, period! By definition, my _intention_ is
> therefore to declare these three attributes as containing "boolean" values.
I suppose, since anything can have the "true" or "false" properties,
you could roll your own boolean type like so:
class bool { }
Then
my bool $electricity;
Can contain nothing at all. But it can be true or false, since
"everything is a boolean." I like that idea. You would use it (a tad
awkwardly) as such:
$electricity but= true if $plug;
$electricity but= false if $short_circuit;
Luke
