Chapter 3.1: If, Also If, and Otherwise

Conditions

It is very common that programmers use conditions in their code. Conditions are a way to execute code if something meets a certain criteria. The if statement is a great example.

obj x = 10;

if x == 10 { # '==' is a operator to check if something equals another value
    bark("x is 10!"); # since x is 10, this code will always be ran inside the 'if' block.
}

== is what we call a boolean operator. These are different from math operators, as they compare two values instead of changing them.

• == compares two values to see if they are the same
• != compares two values to see if they are not the same
• > compares two values to see if one is greater than another
• < compares two values to see if one is less than another
• >= compares two values to see if one is greater than or equal to another
• <= compares two values to see if one is less than or equal to another

The if statement takes a comparison (often called an expression) to determine if the value is true or false. If true, run the code, otherwise ignore and continue.

obj x = 10;

if x != 20 {
    bark("thank goodness, x is not 20!");
}

You might also want to run code if the first if statement fails. That can be done with the otherwise statement, following a if statement.

obj x = 10;

if x == 11 {
    bark("x is 11!");
} otherwise {
    bark("x is anything but 11!");
}

otherwise is often thought of as the "default" case. If any comparisons above are not true, otherwise will run. That means we can sandwich alsoif statements between to create proper control flow for our program!

obj x = 10;

if x == 0 {
    bark("x is 0!");
} alsoif x == 10 { # as many 'alsoif' as you like!
    bark("x is 10!");
} alsoif x == 20 {
    bark("x is 20!");
} otherwise {
    bark("x is anything but 0, 10, or 20!");
}

Your Challenge 🤔

Use an if statement to determine if x is greater than or equal to 10, then output the message "Control flow is easy!"

Answer

obj x = 10;

if x >= 10 {
    bark("Control flow is easy!");
}