Working with Numbers

In order to start irb open your terminal and type irb, then hit the return key (enter). In order to quit irb again (and get back to your system shell prompt) you can type exit or press ctrl-d, which does the same.

Exercise 1.1

In irb, calculate:

• How many hours are in a year.
• How many minutes are in a decade?
• How many seconds old are you?

Exercise 1.2

What do you think happens when you combine the following floats and integers?

Try computing these in irb:

• 3.0 / 2
• 3 / 2.0
• 4 ** 2.0
• 4.1 % 2

Is the result a float or an integer?

Exercise 1.3

Methods are a way of “doing something with an object”. E.g. in Ruby, numbers have two methods that allow you to check whether the number is odd or even.

Look through the documentation for integer numbers (called Fixnum) and find the methods that tell if a number is odd or even.

Exercise 1.4

In irb, use these methods to find out if certain numbers are odd or even. Numbers like 0, 1, 2, 99, -502 etc.

You can use a method by appending a dot . and then the method name to the object. E.g. -99.abs uses (we also say: “calls”) the method abs on the number -99.

Try for yourself what it does, and google for “ruby abs” to find the documentation for this method.