## Swift Subtraction Assignment Operator

In Swift, Subtraction Assignment Operator is used to compute the difference of given value in right operand from the value in left operand, and assign the result back to the variable given as left operand.

In this tutorial, we will learn about Subtraction Assignment Operator in Swift language, its syntax, and how to use this Assignment Operator in programs, with examples.

### Syntax

The syntax of Subtraction Assignment Operator is

`x -= value`

where

The expression `x -= value` computes x – value and assigns this computed value to variable x.

Therefore the expression `x -= value` is same as `x = x - value`.

## Examples

### 1. Subtraction Assignment of integer value to x

In the following program, we shall Subtract assign an integer value of 25 to variable x using Subtraction Assignment Operator.

main.swift

```var x = 70
x -= 25
print("x is \(x)")```

Output

`x is 45`

Explanation

```x -= 25

x = x - 25
= 70 - 25
= 45```

### 2. Subtraction Assignment of an expression to x

In the following program, we shall subtract and assign the value of an expression to variable x using Subtraction Assignment Operator.

main.swift

```var x = 40
var y = 5
x -= (2 + y) * 4
print("x is \(x)")```

Output

`x is 12`

Explanation

```x -= (2 + y) * 4

x = x - (2 + y) * 4
= 40 - (2 + 5) * 4
= 40 - 28
= 12```

### 3. Subtract Assignment with strings

We cannot use Subtraction assignment operator with string values.

main.swift

```var x = "Hello "
x -= "Ram"
print("x is \"\(x)\"")```

Output

## Summary

In this Swift Operators tutorial, we learned about Subtraction Assignment Operator, its syntax, and usage, with examples.