Chapter 3.1: If, Also If, and Otherwise

Booleans

Before introducing conditional programming, it's important to understand boolean logic.

obj x = true;
obj y = false;
obj z = null;

true is 1, and is understood as the true value. false is 0, and is understood as the false value. null is 0 as well, but is understood as the "none" or null value, meaning nothing.

You can get true or false by using boolean operators. These are different from math operators, as they compare values instead of modifying 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
• and compares two values to see if both conditions are true
• or compares two values to see if one (or both) conditions is true

Additionally, not flips a value (true -> false, false -> true)

obj x = 10 == 10; # true, 10 is equal to 10
bark(x) # 1 (true)

bark(not true); # 0 (false)

Conditions

Conditions are a way to execute code if something is true, met by a certain criteria usually from boolean operators. The if statement is a great example.

obj x = 10;

if x == 10 { # x == 10, true
    bark("x is 10!"); # since x is 10, this code will always be ran.
}

The if statement takes a comparison (or any expression) to determine if the value is true or false/null. 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 place also if statements between if and otherwise to create proper control flow for our program.

obj x = 10;

if x == 0 {
    bark("x is 0!");
} also if x == 10 { # as many 'also if' statements as necessary
    bark("x is 10!");
} also if 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!");
}