Re^2: Function Prototype Context Conversion

[tadman]

Well, it is clear the way Perl operates, but that is merely one interpretation of how it could be done. What burned me was that I do this sort of thing all the time with regular, unprototyped functions. It just goes to show you never can be too careful when programming.

I suppose the unfortunate thing is that Perl doesn't differentiate between "scalars" and scalar-like things in the same way that it differentiates between "arrays" and lists. Using prototypes to merely mandate how many paramters should be passed to a function doesn't seem to be the best way to go about it anyway.

Maybe I'm too shell oriented, where I expect things to be automatically expanded before being processed. Meaning, something like this:

% /bin/foo foo_a foo_b foo_c

Where there you have three distinct parameters being passed to /bin/foo and it will complain if it doesn't have, let's say, at least two.

% /bin/foo foo_?

Now here there's technically one element being passed to the shell, which expands it into a list before being proccesed. Same thing goes if you had a variable $FOO which was 'foo_a foo_b foo_c' of course.

In summary, I suppose the only way to do this reliably is something like this:

sub foo
{
      croak "foo() only takes one argument" if (@_ > 1);
      print "$_[0]\n";
}

But you're not likely to see that put into general practice any time soon.

I understand that Perl and the shell are two different things, so this whole thing is really just one big assumption that I made.

The only reason I would even think of Perl functions and command-line programs as the same thing is the whole laissez-faire way of handling arguments that Perl has. They're not typed (normally), they're not named, heck, they're not even declared unless you use prototypes! In that regard, I was figuring that @_ would operate along the same lines as @ARGV since the two are so alike in that respect.

[Abigail-II]

It all has to do with compile time and run time. Prototyping has a compile time effect, while the number of elements in an array isn't known till run time. I fail the see the relevancy of your shell example. Prototyping changes the way perl parses Perl. Expecting no changes when using prototypes is a mistake (if you don't want changes, don't change your code! ;-)).

Abigail