Step 5: Booleans

Another basic data type in Ruby is the boolean. Booleans are actually the most basic type in programming, and correspond to the concepts of true and false.


To demonstrate the concept of the boolean type, paste the following into and hit "run".

1 == 1

On the right-hand side of the REPL, you can see that this expression evaluates to true. The expression is asking the computer if the number 1 is equal to the number 1, which is obviously true.

Here we've also introduced the == operator. In Ruby, == is a comparison operator that tests to see if the values on the left and right of the operator are equal, and returns true if they are and false if they aren't.

Now try this:

1 == 2

This expression evaluates to false, because as we know 1 and 2 are different numbers. Finally, try the following. What do you think it will return?

1 == "1"

This expression evaluates to false because the number 1 and the string "1" are two different things.

false == false
# => true
true == false
# => false
true == "true"
# => false

Pay attention to the last expression above, and note again that just like with strings and numbers, the string "true" and the boolean true are not equivalent.