04-first-functions.md

First Functions

Let's take a look at some predefined basic functions, how to use them and learn how we can define our first own functions.

Defining Values

x = 42 defines the variable x to hold the value 42.

Any variable can only be defined once¹!

We can also use truth values: True and False (capitalized!)

Basic Calculation

Basic calculations work as expected

• 1 * 2
• 2 / 2
• 3 + 1
• 1 - 3

3 + 1 * 20 vs. (3 + 1) * 20

Truth values

• True && False
• True || False
• not False

Comparisons

Comparisons also work as expected.

• 5 == 5
• 3 > 2
• 1 >= 10
• 2 /= 2 (note that not !=)

Define our own

Let's define some functions of our own.

double x = x * 2

six = double 3

isThree x = x == 3

isOneMore x y = x - 1 == y

result = isOneMore 3 6

1. Except in GHCi where defining a value again overwrites previous definitions for convenience ↩