1.4 Integer
Ruby differentiates between whole numbers, or Integers, and decimal numbers, or Floats.
7.class # => Integer
7.0.class # => Float(In fact, you can always call the method .class on any object, ever, at any time, to ask it what class it is.)
We’ll learn about integers first.
1.4.1 Syntax
Integers begin with a digit (0-9) and end when Ruby meets anything other than a digit (a space, a comma in an array, a closing parentheses at the end of method arguments, etc) — except for underscores, which you can use as a delimiter if it helps to understand the number:
10000000 # Is this 1 million? 100 million?
10_000_000 # Ah, it's easier to tell now.1.4.2 Methods
Let’s experiment with some common methods for Integers:
+ - * / % ** (math)
We, of course, have the standard math methods, like the calculator language. These methods all have the same syntactic sugar that the String versions did, so we can say 12 + 5 rather than 12.+(5) (thankfully).
Try each of the following:
12 + 5
12 - 5
12 * 5
12 / 5Whoa! Did you get what you expected for that last one?
It turns out that the Integer version of division will only return another Integer, and so / only returns the whole part (like in elementary school). If you want the remainder, you have to use the % (called the “modulus”) operator. Try this:
12 % 5Another maybe unexpected thing: raising a number to a power, e.g. 32, is not done using the ^ like in many other computing environments. Instead, use the double-star ** operator:
3 ** 2Once you’ve played with the REPL, it’s time to move into the graded project environment.
Open the GitPod Integer project for this chapter and start with the exercise math.rb:
LTI{Load assignment}(https://github.com/bpurinton-appdev/integer-chapter/tree/bp-additions)[MV4dKHMwdAFhfRn752YW3TAY]{KBpPhe42o6wDRi35rWagKY4F}(20)[integer_project]
For a GitPod refresher, see here.
odd? and even?
The .odd? and .even? methods return true or false based on whether the number is, well, odd or even. Don’t be thrown off by the question mark at the end of the method name — it’s nothing special, just another letter. Rubyists like to end method names with a question mark when methods return true or false.
p 7.odd?Return to the GitPod Integer project and work through odd.rb
rand
There’s another special method like p that we are allowed to call “in space”, i.e. not on the right side of a dot
This is another method defined on Kernel, so the longhand would be Kernel.rand(6)., called rand. It returns a random number, and is very useful for all kinds of stuff, everything from games to statistical analysis:
rand(6) # => returns a random integer between 0 and 5Somewhat oddly, rand(n) will return a random integer between 0 and n - 1 rather than between 1 and n. That may seem surprising, but it’s actually pretty handy because a lot of times what we want to do is generate a random offset and it’s convenient for that to include 0 as a possibility.
Give it a try:
# random number between 0 and 8
p rand(9)to_s
We often will want to combine our Integers with Strings when crafting output for our users. Give it a try:
lucky_number = rand(100)
p "Your lucky number is" + lucky_numberUh oh! RTEM!
It turns out that String’s + method can only add two strings together, not a string and an object of some other class. So, a lot of times we’ll need to convert an Integer into a String prior to output. Fortunately Integer has a handy method, to_s (or “to string”), that does just that:
p 98.to_sto_f
Similarly, there’s a to_f (or “to float”) method to convert an Integer to a Float, which is often handy for doing math, as we’ll see next.
BENP: maybe combine to_i, to_f and to_s here in a gitpod exercise / modify integer_birth_year. integer_birth_year could move to dates chapter
Return to the GitPod Integer project and work through birth_year.rb