Ruby check if even number, float

Question

I want to check if the number is even! I tried the following:

a = 4.0
a.is_a? Integer

=> false

a.even?

=> undefined method for Float

S

Answer 1

If you are unsure if your variable has anything after the decimal and would like to check before converting to integer to check odd/even, you could do something like this:

a = 4.6
b = 4.0

puts a%1==0 && a.to_i.even? #=> false
puts b%1==0 && a.to_i.even? #=> true

Additionally, if you want to create an even? method for the Float class:

class Float
  def even?
    self%1==0 && self.to_i.even?
  end
end

a = 4.6
b = 4.0

a.even? #=> false
b.even? #=> true

Answer 2

Just keep in mind how numbers are converted:

(4.0).to_i # same as Integer(4.0)
=> 4
(4.5).to_i
=> 4
(4.9).to_i
=> 4

Using round may be safer:

(4.0).round
=> 4
(4.5).round
=> 5
(4.9).round
=> 5

Then of course you can call even as @Yu Hao wrote:

(4.5).round.even?
=> false

You can also easily observe known floats 'feature':

(4.499999999999999).round.even?
=> true
(4.4999999999999999).round.even?
=> false

Answer 3

Make it an Integer then:

a = 4.0
a.to_i == a && a.to_i.even?  #=> true