how to convert a fraction to float in ruby

Question

I have a string \"1/16\" I want to convert it to float and multiply it by 45. However, I dont get the desired results.

I am trying in

Answer 1

@Farrel was right, and since Ruby 1.9 includes Rational and String has a to_r-method things are easier:

puts ("1/16".to_r * 45).to_f  #=> 2.8125
puts ("1/16".to_r * 45).to_f.round(2) #=> 2.81

In 2.0 it became even easier with a rational literal:

1/16r # => (1/16)

Answer 2

This is the most understandable answer I can think of:

def toFloat(fract)

   str = fract.to_s
   parts = str.split("/")

   numerator = parts[0].to_f
   denominator = parts[1].to_f

   return numerator / denominator

end

puts toFloat(3/4r) # 0.75

puts toFloat(2/3r) # 0.666666666666...

Answer 3

Looks like you're going to have to parse the fraction yourself. This will work on fractions and whole numbers, but not mixed numbers (ie: 1½ will not work.)

class String
  def to_frac
    numerator, denominator = split('/').map(&:to_f)
    denominator ||= 1
    numerator/denominator
  end
end

"1/16".to_frac * 45

Answer 4

Use Rational

>> (Rational(*("1/16".split('/').map( &:to_i )))*45).to_f
=> 2.8125