From: Matthew Kerwin <matthew@...>
Date: 2012-06-14T14:24:13+09:00
Subject: Re: sqrt of rational numbers

Dan Connelly wrote in post #1064519:
> I was a bit surprised when I ran the following
>
> ...
>
> Now it works:
>

On 14 June 2012 14:33, Adam Ms. <lists@ruby-forum.com> wrote:
> No. You broke it. Read the Rational() docs.

I'm only butting in here because I'm genuinely interested; how
precisely is it broken?  I read through
http://www.ruby-doc.org/core-1.9.3/Rational.html and I can't see
anything in Dan's patched Math#sqrt() that defies anything in the
Rational() docs.  Unless I'm not reading the right docs?

Further from what I can see about how Rational reduces floating point
numbers to ratios of integers, checking that the parts of the rational
are perfect squares isn't necessary as the rationalised form has the
same precision as a floating point number.  However in terms of
pretty,
  Math.sqrt(Rational(16,9)) # => (4/3) is nice, but
  Math.sqrt(Rational(17,9)) # => (1547401413261741/1125899906842624)
is much uglier (to me) than 1.3743685418725535

-- 
  Matthew Kerwin, B.Sc (CompSci) (Hons)
  http://matthew.kerwin.net.au/
  ABN: 59-013-727-651

  "You'll never find a programming language that frees
  you from the burden of clarifying your ideas." - xkcd