Section 6 - Relational Operators.md

Booleans

A boolean is a data type that can only hold two values: true and false. Just like the other data types we've seen, you can assign them to variables.

local boolean1 = true
local boolean2 = false

⚠️ Booleans are case-sensitive!

Relational Operators

A relational operator compares two operands and returns a boolean value based on the result. Here's a list of Lua's relational operators:

Operator	Description	Example	Result
==	Equal To: Checks if two operands are equal	5 == 5	true
~=	Not Equal To: Checks if two operands are not equal	8 ~= 8	false
>	Greater Than: Checks if the left operand is greater than the right operand	10 > 3	true
<	Less Than: Checks if the left operand is less than the right operand	10 < 3	false
>=	Greater Than or Equal To: Checks if the left operand is greater than or equal to the right operand	5 >= 5	true
<=	Less Than or Equal To: Checks if the left operand is less than or equal to the right operand	15 <= 8	false

⚠️ Relational Operators aren't Assignment Operators!
Many beginners confuse the assignment operator (=) with the equal to operator (==). Remember, the assignment operator assigns a value to a variable, while the equal to operator checks if two values are equal.

Using a relational operator is similar to using arithmetic operators. Here's an example:

local myValue = 90
print(myValue > 100)

Running this will print out "false". We assign myValue the value 90, then we print out whether it's greater than 100. Since 90 is not greater than 100, the expression evaluates to false.

Here's another example:

local myValue = 40 >= 35
print(myValue)

Running this will print out "true". We assign the result 40 >= 35 to the variable. Since 40 is greater than 35, the expression evaluates to true, and that is stored in myValue.

You can also compare strings.

local fruit1 = "Apples"
local fruit2 = "Bananas"
print(fruit1 == fruit2)

Running this will print out "false" because the values of fruit1 and fruit2 are not equal.

Relational Operators with Two Different Types

When comparing two operands with different data types, you can use the equal to operator (==) or the not equal to operator (~=). For example:

print(5 == "5")

Running this will print out "false" because the two operands have different data types (number and string), so their values cannot be equal.

However, you cannot use other relational operators to compare operands with different data types. For example:

print(5 <= "5")

This code will cause an error because you cannot compare a number with a string using the less than or equal to operator.

Relational Operators with Strings

We've went over that you can use == and ~= to compare strings. But what happens if you use other relational operators?

In Lua, when you compare two strings using other relational operators, they are compared in alphabetical order. For example:

local string1 = "red"
local string2 = "blue"
print(string1 > string2)

Running this will print "true" as "red" comes alphabetically after "blue".

String comparisons are case-sensitive. If two characters have the same letter but different cases, the lowercase letter is considered alphabetically greater. For example:

local string1 = "Red"
local string2 = "red"
print(string1 > string2)

Running this will print out "false" because the lowercase "r" in string2 is considered alphabetically greater than the uppercase "R" in string1.

Quiz

Do not run these code snippets.

1.) What does this print?

print(true == false)

Solution

false

2.) What does this print?

local myVariable = 2 + 5
print(myVariable <= 7)

Solution

true

3.) What does this print?

local myCurrentValue = 10

print(myCurrentValue + 5 > 20)

Solution

false

4.) What does this print?

local variable1 = 5
local variable2 = variable1 >= 5
print(variable2)

Solution

true