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# Operators
We have seen the four basic math operations in elementary school: addition, subtraction, multiplication, and division. In Swift, we can use operators to perform these operations.
### Basic Operators
```swift
var a = 0
a = a + 10
a = a - 5
a = a * a
a = a / 10
```
The following lines are equivalent:
These operators are self-explanatory; however, if we were to take a closer look at the the line `a = a / 10` we can notice that the output is `2` instead of `2.5`. The reason for this is because the type of `a` is an `Int`. If we were to perform these operations on `a`, then we must also use an `Int`.
Then, how do we get the value `2.5`? Because the type of `a` is an `Int`, then we must introduce a new variable of type `Double` or `Float` since we cannot change the type of a variable once initialized. We would also need to make sure that the values in which we apply these operators on must also be a `Double` or `Float`.
Let's take a look at the line `Double(a)`. This is known as **type casting**. Because `a` is an `Int` and we needed a `Double`, `Double(a)` converts the value `2` to `2.0`. Note that this **does not** change the type of `a`. It only produces a value to be used for that operation.
One more common operator we may see is the **modulus** operator (`%`). This is similar to the `/` operator except we return the remainder.
### Common Operators
The following is a list of common operators that we are likely to use.
| `>` | greater than | `\|\|` | or |
| ---- | ------------------------ | ------ | --- |
| `>=` | greater than or equal to | `&&` | and |
| `<` | less than | `!` | not |
| `<=` | less than or equal to | | |
| `==` | equal to | | |
| `!=` | not equal to | | |
### String Interpolation
**String interpolation** is a way of combining variables and constants inside a string. Take a look at this example:
```swift
var name = "Vin"
"My name is \(name)."
```
Of course, we could have used the `+` operator to concatenate these strings together.
The problem with this approach is efficiency especially if we want to concatenate multiple variables. Another issue with using `+` is that Swift does not allow types such as `Int` or `Float` to be glued with a `String`.
We could cast `age` to a `String` but that would be expensive.
Using string interpolation is a lot more efficient and looks cleaner too!