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Ruby Basics

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Numeric Types

2:32 with Jay McGavren

Programming languages use strings a lot, but they use numbers even more often. Numbers in Ruby can be used in all the math operations that other programming languages support. But unlike in most other languages, numbers in Ruby are also objects. That means they have lots of useful methods attached to them, just like with strings.

Here we have some code that assigns the integer 12 to a variable named whole_number, and the fractional number 12.34 to a variable named fractional_number. That dot within the numbers is important, because it decides which of Ruby's two most common numeric classes the number gets assigned to.

whole_number = 12
fractional_number = 12.34
p whole_number.class # Fixnum [Integer in Ruby 2.4 and later]
p fractional_number # Float
  • If we set fractional_number to 12.0, it'll still be treated as a Float. The key is whether it contains a decimal place or not.
  • The distinction between Fixnum/Integer and Float classes is important, partly because it affects what methods are available on a number.
  • If the number in your code has a decimal point, it's a Float. Otherwise, it's a Fixnum/Integer.

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    [MUSIC] 0:00
    Programming languages use strings a lot, but they use numbers even more often. 0:04
    Numbers in Ruby can be used in all the math operations that other programming 0:10
    languages support. 0:13
    But unlike in most other languages, numbers in Ruby are also objects. 0:15
    That means they have lots of useful methods attached to them, 0:20
    just like with strings. 0:23
    Here we have some code that assigns the integer 12 to a variable 0:25
    named whole_number, and 0:30
    the fractional number 12.34 to a variable named fractional_number. 0:31
    That dot within the numbers is important, because it decides which of Ruby's 0:35
    two most common numeric classes the number gets assigned to. 0:40
    Let's print out the class for each of these numbers, so 0:43
    we'll call the class method on the value and 0:46
    store it in each of those variables, save that, try running it, 0:50
    The value in whole_number is a Fixnum, which is a kind of integer. 0:57
    The value in fractional_number is a Float, as in a floating point number. 1:02
    Let's try setting fractional_number to 12.0, and 1:08
    see if it's still treated as a Float. 1:10
    It looks like it is. 1:16
    They key is whether the number contains a decimal place or not. 1:17
    The distinction between Fixnum and Float classes is important 1:21
    partly because it affects what methods are available on a number. 1:25
    Let's bring up a search engine and do a search for ruby fixnum. 1:29
    Just like before, one of the top hits will be a Ruby documentation site. 1:34
    Here on the side we see the even method that we've been calling previously. 1:39
    So let's try calling it on whole_number. 1:45
    Whole_number.even?, don't forget the question mark at the end, save that, 1:49
    and try running it, and we get the result true, because 12 is a whole number. 1:56
    For fun, let's try calling it on fractional_numbers as 2:03
    well, Dot even question mark. 2:05
    Save it, run it. 2:13
    The call to even works for whole_number, but it fails for fractional_number, 2:15
    because that method doesn't exist on the Float class. 2:19
    So remember, 2:22
    it's important to know whether a number in Ruby is a Fixnum or a Float. 2:23
    If the number in your code has a decimal point, it's a Float. 2:27
    Otherwise, it's a Fixnum. 2:30

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