Before we move on to variables, we’ll quickly look at a few of the things that you found out in the previous exercise:
6 / 2
#=> 3
5 / 2
#=> 2
5.0 / 2
#=> 2.5
5 % 2
#=> 1
If you give ruby integers (whole numbers), it will do integer division. For example, 5 / 2 gives 2 as it is the largest whole number of times you can remove 2 from 5. The partner to integer division is the remainder 5 % 2, giving 1. Together these two operations tell you that 2 goes twice into 5 with remainder 1. If you give ruby decimals it will do normal division. Everyone gets caught out by this at some point.
2.even?
#=> true
The line above is actually pretty special. We’ve just asked the value 2 a question and it’s responded. In programming terms, this works because 2 is an object - something that contains both data and methods that can query/manipulate the data. In this case, even? is the method that we called. In ruby all values are objects. This is unusual and isn’t true in many other programming languages. We’ll leave it at that for the time being, but you’ll learn more about this later.
"hello " + "world"
#=> "hello world"
"don't shout".upcase
#=> "DON'T SHOUT"
Here you met a third type of value: "hello" is a string. As you see here, you can add strings together. Like all ruby values, strings are also objects and therefore have methods. Here we used the upcase method, to change the string into uppercase. You can find out more about the methods that strings have in the ruby docs.
"Bob" + 3
# TypeError: can't convert Fixnum into String
# from (irb):1:in `+'
Oh dear! Turns out that you can’t add a string to an integer. Have another read of the message that irb gave you. Can you figure out what it is saying? When something goes wrong, ruby tries to be as helpful as it can. Learning to interpret the errors that ruby gives is an important part of learning to become a programmer.
The ^ operator in the optional challenge is bitwise exclusive or.