Question

Maybe the title is confusing, but I will try to explain with examples:

Given a float with precision = 2, I want to be able to round either to its closes integer, or to its closest .5. Examples:

Given: 4.12 --> 4
       4.24 --> 4
       4.25 --> 4.5
       4.33 --> 4.5
       4.53 --> 4.5 
       4.65 --> 4.5 
       4.75 --> 5
       4.84 --> 5

What would be a good way to do this in Ruby?

Answer 1

Multiply by 2, round, divide by 2.

[4.12, 4.24, 4.25, 4.33, 4.53, 4.65, 4.75, 4.84].map do |x|
  r = (x * 2).round / 2.0
  r.to_i == r ? r.to_i : r
end

=> [4, 4, 4.5, 4.5, 4.5, 4.5, 5, 5]