Ruby Number Methods

One of the biggest advantages of making the Ruby Monkey library was going through all of the Ruby methods for numbers, strings, arrays and hashes. I learnt about so many methods I had no idea existed and discovered some really useful ones. In this post I'm going to look at some of my favourites.

between?

This lets you check if a number is between 2 values inclusive.

So instead of this:

  n >= 10 && n <= 20

You can just write:

  n.between?(10,20)
  => true

digits

This simply returns an array of the digits in the number, from smallest to largest.

29.digits
=> [9,2]

gcd and lcm

These stand for greatest common divisor and lowest common multiple respectively.

The GCD of two (or more) numbers is the highest number that is a divisor (or factor) of all the numbers provided, so for example:

8.gcd(12)
=> 4

This is because the common divisors of 8 and 12 are 1,2 and 4 ... and 4 is the highest.

If two numbers are coprime then their GCD will be 1:

12.gcd(25)
=> 1

The LCM of two numbers is the lowest number that is a multiple of them both, in the game FIZZ BUZZ this will be the first number you say FIZZ BUZZ on:

3.lcm(5)
=> 15

When numbers are coprime the LCM is just the product of the two numbers, but it gets trickier when they have common factors:

12.lcm(30)
=> 60

ordinalize

This one is actually only in Rails as it's part of Active Support, but it's nice to use.

This will just return a string with the correct suffix appended to the number, for example:

1.ordinalize
=> "1st"

Always useful if you're dealing with positions etc.