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We'll start working with operators that we're most familiar with  addition, subtraction and other basic mathy stuff.
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[MUSIC]

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Every programming language allows you to perform basic math like addition,

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subtraction, division and multiplication.

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To achieve these tasks, we use operators.

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An operator is a special symbol or

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phrase that you used to check, change or combine values.

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Operators can be separated into three categories.

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Unary operators.

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These operate on a single target.

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We also have binary operators, ones that operate on two targets and

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ternary operators, those with three targets.

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We'll start with binary operators because they're ones we're most familiar with.

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We've already used an operator or two in this course.

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Let's look at one that I'm sure we all know.

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This is the addition operator.

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It is a binary operator,

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because as we defined earlier, binary operators operate on two targets.

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In this case, our two targets are numbers that we add together.

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The values that operators affect are called operands.

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So in our case, the two numbers are called operands,

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a combination of an operator with operands is called an expression.

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So this line of code that we see here is an expression.

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There are many binary operators most of which you are familiar with

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from basic math.

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The one we just saw, the addition operator, where we also have

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a subtraction operator, division, multiplication and a remainder operator.

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When I was in school I had to learn long division.

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You remember that?

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Feels like forever ago.

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In long division, if you divided 10 by 3,

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3 would fit into 10 three times and you would get a remainder of 1.

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That is what the remainder operator does, it tells us given a number and

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its divisor what is the remainder that is left over.

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It is sometimes also known as the modulo operator.

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While the point of this operator may seem silly, it's actually quite useful.

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If we took a number and a divisor 2 and use the remainder operator.

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If the remainder is 0, well, now we know that this is an even number.

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Those are the main binary operators we'll look at for now, they're pretty simple.

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Something that's interesting to know but not at all necessary

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is that these operators we looked at are called infix operators.

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An infix operator is one that goes in between two operands.

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All binary operators are infix operators.

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So if you're confused about the syntax when writing it out,

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remember that they go in between the values they're working on.

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Let's start by playing around with binary operators for a bit.

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We'll add another page to our playground to talk about operators first.

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So like before click on the first icon in the second set here

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to open up the project navigator.

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And then using the plus button below, the Add button, let's add a new page.

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We're going to call this one operators.

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Let's add a comment in here.

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We're going to talk about binary operators first.

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Okay, so let's say we have the height and width of a room in feet.

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Yeah, yeah, I know not everyone lives in the US and uses feet.

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Don't worry, we'll work around that.

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So let's create a new constant height and we'll assign it an integer value.

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So say 12 and I'll add a comment, we'll say in feet.

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We also need the width for this example.

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So we'll say let to create a constant, width for

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the name and we'll assign another integer value.

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Now remember I can also explicitly write out the type like so

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and we'll add another comment in saying in feet.

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Now to calculate the area of the room which is a rectangle,

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we can simply multiply the height and the width.

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Let's do this and assign this to a constant called area.

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We'll assign this new value.

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So we'll say let area equal height times width.

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So this is the multiplication operator, which is the asterisk symbol.

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And it's a binary operator which goes in between two operands like so.

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Now the unit of measurement for this is area in square feet,

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now like I said we don't all use square feet.

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So let's try and convert this into square meters.

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Let's add another comment here.

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So we'll say one square meter equal

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one square foot divided by 10.764.

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Okay, so to get this area in square feet

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into meters square, we can create a new constant.

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We'll call this areaInMeters and

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we'll simply divide the area by 10.764.

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Okay, when you try this, you'll see that we get an error and

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this is because of a conflict between the types.

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Now I don't have an error symbol over here but

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you can see in my console that there is a bunch of stuff going on.

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And you can bring up your console by clicking on the second icon in this set

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of three, the second set.

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Okay, so what's going on here?

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The height and width values are of type int since they're whole numbers.

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And since we're multiplying them to get a value for

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area, Swift infers that the area should also be of type int.

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Now we can't simply combine two types willynilly.

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In real life you could.

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You can simply divide this area which would be 120 by 10.764.

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We know what to do, but the compiler doesn't.

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We cannot divide an int by a value of type double

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because Swift doesn't know which type the answer should be.

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Should the value be an integer value?

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In which case, Swift will go ahead and round off the answer and

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cut off the values after the decimal point.

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Or should it be a double.

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Now we can solve this for Swift by changing the values for height and width

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to be double by either adding decimal points or explicitly specifying the value.

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So we'll say let height double, let width double.

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And now everything should resolve itself.

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So pretty simple stuff as you just saw, we use the multiplication and

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division operators.

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But it's important to know that unlike in the real world,

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you have to be careful about what types you use.

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You can't simply divide an integer by a double or even multiply it.

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In the next video, let's take a look at some other binary operators.
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