You need to round the number in the array. ruby

Question

I have my code as

out = 0.step(10, 0.1 ).to_a
puts out

and when i run it some numbers are output as 5.1000000001, please tell me how to round these numbers so that the output would be 5.1

Output image

Answer 1

Use 0r.step(10r, 0.1r) for exact calculation (use .to_f at print time) since Rational numbers don't have the same precision issues that floating point numbers do. E.g.

0r.step(10r, 0.1r).map(&:to_f)

Alternately (and equivalently, for languages that don't have rationals), use integers and divide when you need them:

0.upto(100).map { _1 / 10.0 }

Dividing as the last operation instead of cumulatively adding minimises the floating point error.

While it is much better to not have an error in the first place, using one of the above methods, you could also try to rescue your inexact numbers by rounding:

0.step(10, 0.1).map { _1.round(1) }

Answer 2

Alternatively, if the numbers are close enough for the sake of the calculations you're doing, and the issue is only with printing, you can simply format them as you see fit.

out = 0.step(10, 0.1).to_a

out.each do |n|
  printf "%.2f\n", n
end