On 5/1/07, Smylers <[EMAIL PROTECTED]> wrote:
What are the situations in which a programmer really needs to open
something but doesn't know wether that thing is a file, a directory, or
a URL? I'm still unpersuaded this is sensible default behaviour.
Lots of times. It's an agnosticism, meaning that you can write a
module which opens things and it doesn't have to know what it's
opening; as a matter of fact, it doesn't even have to know what kinds
of things it's *capable* of opening. That's powerful.
The point is, even though opening a file and opening a URL are
reasonably different things, they are both the same logical operation,
so they can be abstracted. Not abstracting them will either cause
modules to have to take a "type of file" parameter whenever they take
a file, or will lead to code like this:
my $fh = do given $file {
when /<url>/ { openurl($file) }
default { open($file) }
}
And the programmer of this module may not have been aware that he
could operate on directories, even though it's just some sort of line
processing module.
Anyway, my point is that the concept of opening something is
abstractable, and not abstracting it means that everyone has to
abstract it separately.
And please don't argue from the standpoint of security holes. Security
holes are possible in every language which talks to the outside world.
Taint mode is a pretty good way to keep security holes out of a
complex, rich language like Perl. But if you really want to be free
of security holes, you either have to make a language which doesn't do
anything, or make a language in which everyone can be an expert within
an hour.
Luke
