From: Colin Bartlett <colinb2r@...>
Date: 2010-01-02T21:08:02+09:00
Subject: Re: Rounding float in ruby via .round

On Sat, Jan 2, 2010 at 2:13 AM, Phillip Gawlowski <pg@thimian.com> wrote:
> Hmmm..
> irb(main):001:0> RUBY_VERSION  #=> "1.9.1"
> irb(main):002:0> 3.14567534.round  #=> 3
> irb(main):003:0> 3.14567534.round 3  #=> 3.146

I didn't know 1.9 had extended Float#round. That's useful. Thank you
for the information.

But I'm not sure that Float#round should be allowed to have
non-integer arguments:

# IRB Ruby 1.9.1
n = 9876.54321
  f = 1.75
  r = Rational(7, 4)   #=> (7/4)
  c = Complex(f, 0)    #=> (1.75+0i)
  ci = Complex(f, 2)   #=> (1.75+2i)
n.round     #=> 9877
n.round 0   #=> 9877
n.round -1  #=> 9880
n.round 1   #=> 9876.5
n.round f   #=> 9876.5
n.round r   #=> 9876.5
n.round c   #=> 9876.5
n.round ci  # RangeError: can't convert 1.75+2i into Integer

# it's nice that Integer#round is consistent with Float#round
i = 9876
i.round     #=> 9876
i.round 0   #=> 9876
i.round -1  #=> 9880
i.round 1   #=> 9876.0

# Rational#round: an opportunity for someone?
r = 9876 + Rational( 54321, 100000 ) #=> (987654321/100000)
r.to_f     #=> 9876.54321
r.round    #=> 9877
r.round 1  # ArgumentError: wrong number of arguments(1 for 0)