From: GOTO Kentaro <gotoken@...>
Date: 2002-09-14T04:42:32+09:00
Subject: Re: float precision

At Sat, 14 Sep 2002 02:54:56 +0900,
Daniel Bretoi wrote:
> irb(main):001:0> a = 20020912.194220
> 20020912.19
> 
> Why do I miss the last 5 digits when I try to assign a?

Those were omitted by Float#inspect method. 
irb calls #inspect for each result and reports that without quote. 

  a = 20020912.194220
  a == 20020912.19       #=> false
  a == 20020912.194220   #=> true

Give format and you will get all digits:

  irb(main):001:0> a = 20020912.194220
  20020912.19
  irb(main):002:0> sprintf("%.6f", a)
  "20020912.194220"

ieee754hack.rb explains more details of internal representation:
http://www.notwork.org/~gotoken/ruby/p/as-is/ieee754hack.rb

-- Gotoken