Course of Raku / Essentials / Numbers

# Operations with numbers

There is no doubt you already know some of the operations you can do with Raku numbers. Just to mention that the symbol of the *operation* is called an *operator*. The objects on which we perform operations are called *operands*.

## Arithmetics

Operator |
Operation |

`+` |
Addition |

`-` |
Subtraction |

`*` |
Multiplication |

`/` |
Division |

As Raku supports Unicode really well, some of these operators have non-ASCII equivalents:

`×` |
Multiplication |

`÷` |
Division |

To change the order of execution, use parentheses:

```
say 3 * 4 + 5; # 17
say 3 * (4 + 5); # 27
```

## Modulo

The modulo operator is `%`

as in many other languages.

`%` |
Modulo |

It returns the remainder of the integer division of two numbers, so `10 % 3`

is `1`

. Note that `-10 % 3`

is `2`

as the result of the operation is defined as the difference between the first number and the rounded-down division multiplied by the second number. So, `$a % $b`

is equivalent to `$a - $b * floor($a / $b)`

.

## Divisibility

Raku adds a useful operator to test if the number is divisible by another number.

`%%` |
Divisibility |

This is an infix operator that needs two operands: `10 %% 3`

. If the first operand is divisible by the second operand, the result is a Boolean `True`

. Otherwise, `False`

.

## Integer operations

There are special operations that return integer results. Their operators are words instead of symbols.

`div` |
Integer division |

`mod` |
Integer modulo |

The `div`

operator rounds down the result, so `10 div 3`

is `3`

, and `-10 div 3`

is `-4`

.

Both `div`

and `mod`

expect integer operands. So, the following program will not work if you uncomment the lines marked as `Error`

:

```
say 10.3 % 3; # OK
# say 10.3 mod 3; # Error
say 10.3 / 3.3; # OK
# say 10.3 mod 3.3; # Error
```

## Power

There are two ways of getting the result of *x* to the power of *y*. First, you can use the `**`

operator:

```
say 3 ** 4; # 81
```

Second, you can use superscript digits, for example:

```
say 3⁴; # 81
```

It is possible to put more than one superscript digit to get the value of power bigger than 9. For example:

```
say 2¹⁵; # 32768
```

Negative power is not a problem either:

```
say 2 ** (-2); ## 0.25
say 2⁻²; # 0.25
```

Notice that the result of the last two expressions is a `Rat`

number.

## Operations with assignment

All the operations support the shortcut syntax when you need to update the variable. Let us demonstrate it on the example of `+`

.

The full form

```
$a = $a + $b;
```

is equivalent to:

```
$a += $b;
```

## Course navigation

← Numbers / Floating-point numbers | 💪 Exercises: Numbers →