Logic: If/Else And Operators

Quick reference

• 00:01 Okay, in this video, I want to start to look at multiple comparisons,
• 00:06 multiple conditionals.
• 00:08 And in the last video, we looked at a basic if else statement,
• 00:11 where we're just testing for one thing, is a greater than b?
• 00:14 If it is, do this, if it's not, do something else.
• 00:18 But oftentimes, you need to test against more than one thing at once, right?
• 00:22 And you can do that in a couple of different ways using the and
• 00:26 operator or the or operator.
• 00:27 In this video, we're going to look at the and operator.
• 00:29 In the next video, we're going to look at the or operator.
• 00:31 They're very similar but subtly different.
• 00:33 So let's come through here and
• 00:34 let's just get rid of this else statement just to make this a little less confusing.
• 00:37 So here we see if a is greater than b,
• 00:40 then we just want to output this to the screen.
• 00:42 And if we run this, we know what's going to happen,
• 00:45 it's going to say 20 is greater than 19, all right?
• 00:48 So what if we want to test more than one thing?
• 00:51 Well inside of here, we can use the and operator, which is the double and sign.
• 00:56 And now, after that we can run another comparison.
• 01:00 So we could say && a = b, right?
• 01:05 So if a is greater than b and it equals b, then print this out.
• 01:10 Now, obviously this is not going to evaluate to true
• 01:13 because a can't be greater than n and equal to b.
• 01:16 So that's kind of weird, but if we run this, we can see sure enough, no, right?
• 01:22 So maybe this is a bad example.
• 01:25 So let's say if a is greater than b and
• 01:29 a is greater than 100, right?
• 01:33 Okay, that's still going to evaluate to false.
• 01:36 We run this, nothing happens, right?
• 01:39 So let's go ahead and change this.
• 01:40 Let's change this to 200.
• 01:42 Now a is greater than b, 200 is greater than 19 and a is greater than 100.
• 01:50 So here if we run this and notice it says 200 is greater than 19, right?
• 01:56 So in order for this double and operator to evaluate to true,
• 02:02 both of these conditions must evaluate to true.
• 02:06 And that's the difference between and and or,
• 02:08 we'll talk about that a little bit in the next video.
• 02:11 So that's and.
• 02:12 You can do it all on one line like we've done here or you can break this apart.
• 02:17 A lot of times you see something like this because it's just sort of easier
• 02:22 to read maybe.
• 02:23 I don't know, if we save this and run it,
• 02:26 really we're going to get the exact same output 200 is greater than 19.
• 02:31 It's just a matter of style really.
• 02:33 If it's going to be not very complicated, I might do it all on one line.
• 02:40 If you're going to have multiple and statements, it might make sense
• 02:44 to break them apart like this, just so it's a little easier to read.
• 02:48 Again, that's just a matter of personal style.
• 02:51 And as a coder you'll develop into your own style what you like to do.
• 02:56 But here we can have as many of these as we want.
• 03:00 So you can say and a is less than 1000, right?
• 03:03 It doesn't matter how many we do, they still all have to evaluate to true
• 03:08 in order for this whole thing to evaluate to true when we're using and.
• 03:13 So if we save this and run it, again we're going to get the same thing,
• 03:19 200 is greater than 19.
• 03:21 Because 200 is greater than 19, 200 is greater than 100, and
• 03:26 200 is less than 1000.
• 03:28 So all three of these things are true, so it evaluates to true.
• 03:31 So that's how you can use multiple comparisons,
• 03:34 multiple conditionals in your if statements using and.
• 03:37 In the next video we'll look at or.

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