 As I record this video, I respectfully acknowledge that I am standing on the unceded traditional territory of the Comox First Nation. And this video is all about the way jig represents empty shapes. So I've declared variables ahead of time. Jig has been loaded, as you can see in the first line. And A just has an empty line. That's what the textual display shows me. B down here, but if I go back up to A, there is what jig shows me. And what jig shows me is there is this outline around a clear white space. And the white space immediately, I happen to know, means that there's nothing but zeros in the shape. That shape has nothing but zeros in it. And I can verify that by clicking on it. And I get an integer of shape zero. So that is what A actually is. And it would just skip a line, because it's got one line that's empty. That's shape zero. So now let's take a look at B. Hit return on B, and it just goes to the next line. So a bit different than A. It doesn't skip down a line, it just goes right to the next line. So why is it to be doing that? Well, in this case, I see a really dark shape here. And whenever I've got a non-zero leading axis, that's when I've made it darker. So right away, I know the very first number in the shape is going to be non-zero. I can verify that. And the shape is actually 101. So it's got one table with no lines, and it's one item long. If it had a line, it would be one item long. It doesn't have lines. And that's why it immediately goes to the next line. There are no lines to show. So whereas A, it was a zero shape, it was an empty line. When you have a zero in these two leading indices, that means there's no lines to show. You go right to the next line. We'll start to see that happen more often too. So let's just get rid of that. And where were we down here? C. Let's take a look at C. And C does the same thing. Just jumps to the next line. But when we look at Jig, now it's doing it in a slightly different way. You'll notice this is wider. Because this is still dark, we know it's got a non-zero leading axis. I click on this, I see that the four means that it's wider. There would be more items. Now, of course, there are no lines, which is why it jumps to the next line. But because it's four, it's going to be wider. So Jig is able to show me some visual information that tells me exactly what I'm dealing with. D looks exactly the same. This is getting a bit repetitive, isn't it? Well, it's different. This time, it's another clear space. What does a clear space tell me? It tells me there's nothing but zeros in the shape. So again, I can verify that. The shape is zero, zero. So it's got no items and no lines. Jumps to the next line. And this little shape is actually one that's very commonly used in J to immediately return nothing. So if you get to an end of a function you want to act like it's not returning anything, and just go to the next line ready for the next input, you return a shape of zero, zero. No lines, no items, and it just jumps down. And that's quite common. But that's what it looks like in J. It's white because it's zero, zero in the inside. In here, the shape, nothing but zeros. And that's the way Jig represents it. Now let's do E. E return is the same thing. So let's see what's different about this one. OK, now this one again, it's a lighter gray. What that tells me is the leading axis is not non-zero. So there's going to be a zero in the leading axis. If there was a non-zero in the leading axis it would be a darker gray. The medium gray means the leading axis is zero. So I know leading axis is zero, and I look at this width and I know it's going to be wider. So let's see, the shape is zero, four. The leading axis is zero, and the width is four because there would be four items, but there's no lines. So that's why it just jumps to the next line. So let's put in F. Same thing again. Well, what's different about this one? Let's see. Oh, OK. In this one, I can see that the leading axis is non-zero because it's darker. So that tells me this looks like it's the same width four. So I'm guessing at this that the items in the shape are four and they are. The zero in the middle is what makes it an empty shape and the three leading is what makes this darker in Jig. But when you go to the textual version, it's just doing the same thing. It's just jumping down a line. Nothing more than that. So there's not a lot that it's showing. Well, let's go to the next one. Oh, now this is different again. So you see how far it jumped down here? All the way down, I'll put an H down here just to mark it. But down to there. So now let's see what Jig says. OK, so Jig looks at this and says, OK, this is interesting. It's got a non-zero leading edge. It's also really skinny. So that makes me think that there's probably no items in the rows. So that last item in the shape or last axis in the shape is a zero. That's why it's so narrow. And then the two in the one, well, the two gives you the non-zero leading axis and the one is just there in the middle. So that's why you get that kind of a shape. But it's really skinny because there are no items in the row. Now let's look at H. OK, we're back to this thing where we've got no lines to show. Let's see what we've got, actually, though. OK, now here we've got dark. So it's got a non-zero leading axis. Again, it's wide, so we know from experience this is probably about width 4. And it's empty. So there's at least one zero in the shape. And there's the zero that comes in the shape. It's four items, which is the widths wider. Four items in a row, but there are no rows. And there's one table. And then there's one, what do you call them, extra tables? Maybe it's a brick. I can't remember how they go in the higher dimensions. But the point is it's darker because that leading dimension is non-zero. So that's jig. It shows you a lot more information visually than what the textual representation of stuff can in J. And that really makes it valuable if you happen to be dealing with empty shapes. Because empty shapes can really value up. If the number of dimensions is wrong, you're going to get length errors. Things like that are going to happen. But jig will show you right away what's going on and why things are working the way they are. So hope that helps you out and you have a good sense of how empty shapes are represented in jig.