rwmj on A nice, little known C feature: Static array indices in parameter declarations

Comment on A nice, little known C feature: Static array indices in parameter declarations parent

Larry Wall (author of Perl) used this as an argument for "sigils", that is, putting $/@/% in front of every variable.

http://stackoverflow.com/questions/1091634/why-do-perl-varia...

(I merely state this as fact and offer no judgement!)

Deleted my previous comment because it was wrong (I was saying that it didn't help with the names of subroutines). It appears you can even have subroutines named after keywords, but only as long as you put "&" in front of it when you call it:

    sub while
    {
        print "It works!\n";
    }

    &while();

I guess it is still the case that you can break perl code by adding keywords, if it collides with a subroutine that is called with the "&" symbol. Seems most code doesn't use "&" though, but it's a relatively quick fix.

leviathan 13y

Calling a sub with & has a special meaning, it exposes the current argument list @_ to the called sub. That's why you don't see it in most code.

drivers99 13y

I did not know that. Interesting. However, it only works if you call the sub without parentheses like this: &foo

Calling it with parentheses like &foo() would make @_ empty inside of foo. (Or if you said &foo("whatever") it would pass that as @_ instead.)

    sub while
    {
            print "@_\n";
            &foo();
    }

    sub foo
    {
            print "@_\n";
    }

    &while("a","b","c");

produces:

    a b c
    (blank line)

as the output, and

    sub while
    {
            print "@_\n";
            &foo;
    }

    sub foo
    {
            print "@_\n";
    }

    &while("a","b","c");

produces:

    a b c
    a b c

as the output. At any rate, back to the original topic: it still doesn't prevent new keywords from potentially colliding. Oh well.

tolmasky 13y

I prefer the objective-c method of putting @ in front of every keyword.

dietrichepp 13y

Well, I might be upset if this were true for all keywords.

    @static @inline @unsigned @int ilog2(@unsigned @int x)
    {
        @for (@unsigned @int i = 0; i < 32; i++)
            @if ((x >> i) == 0)
                @return i;
        @return 32;
    }

I'm a bit dizzy looking at that code, let me sit down for a moment.

redial 13y

I believe the @ is used only by the obj-c keywords and not the ones from C. So it'll be something more like this

    @autoreleasepool{
        for (int index = 0; index < 100; index++){
            int error = [MyObject performSelector:@selector(addCoolFilterToImage:)];
            if (error) {
                return 32;
            }
        }
    }

dietrichepp 13y

Yeah, that was kind of my point.

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