From: Paul Lutus <nospam@...>
Date: 2006-12-06T07:30:07+09:00
Subject: Re: number format

Bernard Kenik wrote:

> You can use the number.round method, but this doesn't take a number of
> decimal places.
> 
> To round 1.234 to 1.23 use this code:
> x = 1.234
> x = x * 100 # -> 123.4
> x = x.round -> 123
> x = x / 100.0 => 1.23
> 
> At least, that's the best method I can find from the Ruby docs...

Second reply to the second copy of this identical post. This is not a good
idea. The problem is that Ruby's numbers are stored internally in binary
form, and this multiply -- truncate -- divide process will not work as
intended for a lot of numbers.

It is better to retain the full resolution of binary numbers internally, and
simply print the number with the desired number of decimal places:

--------------------------------

#!/usr/bin/ruby -w

0.upto(10) do
  n = rand() * 100
  printf("%5.02f\n",n)
end
--------------------------------

Output:

18.64
61.11
58.18
61.80
93.98
50.86
55.28
44.93
87.23
 1.38
11.63

-- 
Paul Lutus
http://www.arachnoid.com