0:00:01.250,0:00:03.667
Here's where we left off[br]with our coin-flipping game.

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We started out by generating[br]a random number between 0 and 1,

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and then rounding that number[br]to the nearest integer.

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So this gave us a number[br]that was either 0 or 1.

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And then we illustrated[br]our super-realistic coin with this ellipse

0:00:15.909,0:00:18.908
that was either purple or yellow,[br]depending on what the number was.

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And here's the code where we did that.

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So we said if integer is equal to 0[br]set the fill code to be purple,

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otherwise, set it to yellow.

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And then we draw the coin down here.

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But now I've decided[br]that actually my coin has 3 sides.

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Yep, a 3-sided coin.

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So let's add that third side.

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I'm going to start by making[br]a number between 0 and 2,

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so after we round that, it will give me[br]an integer that's either 0, 1, or 2.

0:00:41.533,0:00:45.608
But if we look at our drawing code,[br]we're only accounting for 2 cases here.

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So if integer is 0, make it purple,[br]otherwise, make it yellow.

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But now, otherwise can mean[br]either 1 or 2.

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But wait, what if I did the same thing[br]that we did before,

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but inside this else block?

0:00:56.675,0:01:00.748
So I'm just going to say:[br]if integer is equal to 1,

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then set the fill color to be yellow,[br]like it was before,

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else, we will set the fill color [br]to be red.

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Red's pretty good.

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So what this means is,

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if integer is equal to 0,[br]set the color to be purple,

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otherwise, if it's 1,[br]we will make it yellow;

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otherwise, that is,

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if it wasn't 0, it wasn't 1,[br]it must be 2, we'll make the color red.

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I press restart a bunch of times.[br]It works! Woohoo!

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So then if I wanted[br]to add more sides to my coin,

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I can go up here, make it 0 to 3,[br]and then go deeper into this else block

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and add more if-else's[br]and so on and so forth,

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until I have a bazillion nested blocks.

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And only then will I realize this code[br]is disgusting! I mean gross!

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Code is supposed to be easy to read[br]and pretty, not as ugly as possible.

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So here's what we're going to do:

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Whenever you have[br]just a single if statement

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or an if-else statement[br]inside an else block,

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so that means we're not doing[br]anything else outside of these blocks,

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we're not setting the stroke color,

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we don't have anymore[br]if statements, nothing.

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All we have is that one if statement,[br]and maybe it comes with an else block.

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Then we can actually combine[br]this condition with the line before

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and say, else if integer is equal to 1,[br]then set the fill color to yellow.

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And then this last else block[br]isn't nested anywhere,

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just comes at the very end all by itself.

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Great! So now what this means is

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if integer is equal to 0,[br]set the color to purple,

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otherwise, if integer is equal to 1,[br]set it to yellow,

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otherwise, so if both of these were false,[br]then set it to red.

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I press restart a bunch of times,[br]you can see it still works.

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Great! And the cool thing about this is[br]we can have as many else-if's as we want,

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which makes it really easy for me[br]to add more sides to my coin.

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So let's do that now: I'm going to make[br]a number between 0 and 3,

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and then just add one more else block

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that says else if integer is equal to 2

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we'll set the fill color to... well,[br]it's red before so we can keep it red.

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And then this last else block will be[br]for when an integer is equal to 3,

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it will make it blue. Great!

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All right.

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So in order to do this, you always have[br]to start with an if statement,

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and then you can have[br]as many else-if's as you want,

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and then this last guy is optional.

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We can actually do without it,

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and then it's possible[br]that all of these will be false,

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so none of these blocks gets executed.

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But as long as we have that there,

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then exactly one of these blocks[br]will be run.

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Cool? Now this is a case[br]where it doesn't really matter

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if you say if else-if else-if else,

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or just use plain old if statements[br]like we had in the beginning,

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so if integer is equal to 3.

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And that's because it's never possible

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for integer to equal 0,[br]and then also 1, 2, or 3.

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Great. So these conditions[br]are all mutually exclusive.

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Only one of these blocks[br]will ever get run anyway.

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But that's not always the case.

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What if we try to make a game[br]like this without rounding to an integer?

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So I'm going to get rid of this part[br]where we round it,

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and the other part[br]where we draw it to the screen.

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And let's make up[br]some new rules to my game.

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So I'm still generating[br]a number between 0 and 3,

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put some more tick marks[br]on our number line.

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So let's say that if the number falls[br]between 0 and 1, we will make it purple.

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Oh, that doesn't look like a 'p' at all.[br]You get the idea. OK.

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And then if it's between 1 and 2,[br]we can make it yellow.

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And if it's between 2 and 3,[br]we will make it red.

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Great. So let's see how we can do that[br]with if and else-if's.

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So I can start out by saying[br]if number is less than 1,

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so if it's less than 1,

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and I know it's between 0 and 3,[br]then it must be in this range,

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then I'll set the fill color to be purple.

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Otherwise, if the number is less than 2,

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I can set the fill color[br]to be yellow, 255...

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And otherwise,[br]I'll set the fill to be red.

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Great! And it works just as intended.

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So if the number was less than 1,[br]then again, it's in this range.

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Otherwise it's greater than or equal to 1,[br]but it's also less than 2,

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so that puts it in this range,[br]so we're going to set the color to yellow.

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Otherwise, it must be greater[br]than or equal to 2,

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so it's going to fall in that range.

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And here's a case

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where we couldn't just say[br]if number is less than 2,

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and if number is less than 3,

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because if number is less than 1,[br]then it's definitely is less than 2

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and it's also going to be less than 3.

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So our coin[br]is always going to end up red.

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And that's why in this case,[br]it's really helpful to have else-if.