Numbers

Introduction

Ruby has several different types of objects for representing numbers. We're going to focus on two:

• Fixnums
• Floats

Fixnums represent integers: 1, 3, 10, 90332... Floats represent numbers with decimal points: 1.3, 10.0, 9.00000001...

Checkout the Fixnum and Float documentation. Bookmark these pages! Look at the "Methods" column on the left-hand side.

Operations

Ruby can perform all the standard mathamatical operations:

    puts 40 + 2 # Addition:       will print 42
    puts 49 - 7 # Subtraction:    will print 42
    puts 2 * 3  # Multiplication: will print 6
    puts 6 / 2  # Division:       will print 3
    puts 2 ** 3 # Exponentiation: will print 8

Integer Division

When we divide two integers in ruby, our answer also has to be an integer. For example:

    puts 6 / 2  # will print 3
    puts 7 / 2  # will print 3, ignoring the remainder of 1
    puts 11 / 3 # will print 3, ignoring the remainder of 2

Try this in pry!

Ruby only calculates the number of whole times that a divisor can divide another number. Aka.. it rounds down.

The Modulo Operator

If we are interested in the remainder, we can use the modulo operator:

    puts 6 % 2 # will print 0, 6 is divided evenly by 2
    puts 7 % 2 # will print 1, there is a remainder of 1 when 7 is divided by 2
    puts 11 % 3 # will print 2, there is a remainder of 2 when 11 is divided by 3

Try this in pry!

To force a floating-point answer, we can make one of our operands a Float:

    puts 7.0 / 2 # will print 3.5
    puts 7 / 2.0 # will print 3.5

Shorthand

Ruby has a nice shorthand for combining arithmetic with variable assignment:

    a = 5
    a -= 2
    puts a # ==> 3

Try these in pry!

Order of Operations

So far, we have seen expressions with one operator. What happens if we chain more than one together? Let's try this in pry:

    puts 4 - 2 * 5

Just like in mathematics, ruby follows a pre-determined order when deciding which operations to carry out first. Remember this one from algebra? The mnemonic is:

PEMDAS --> "Please Excuse My Dear Aunt Sally"

The table above specifies the order in which mathematical operations are carried out. Parentheses have the highest precedence. addition/subtraction, the lowest.

Other Useful Methods