From: Christian Boos <cboos@...>
Date: 2002-08-15T16:08:11+09:00
Subject: RE: Is this array operation correct?



> -----Original Message-----
> From: George Ogata [mailto:g_ogata@optushome.com.au]
> Sent: Thursday, August 15, 2002 4:14 AM
> To: ruby-talk ML
> Subject: RE: Is this array operation correct?
> 
> 
> > Then, do something like:
> > 
> >  Array.new(3).map { [] }
> > 
> > Is there something shorter/more efficient?
> 
> If you don't like using Array.new, you can #map to a Range:
> 
> (1..3).map{[]}
> 
> (Dunno about efficiency, here.)
> 
> If you're going to map to a fresh Array, though, you may as well use the 
> in-place version:
> 
> Array.new(3).map!{[]}
> 
> 

# Really basic benchmarking (for 1.6.5 ) ...
def time_it
  GC.start
  now  = Time.now
  yield
  Time.now - now
end

time_it { Array.new(100000).map {[]} }
0.611
time_it { Array.new(100000).map {[]} }
0.631
time_it { (1..100000).map {[]} }
0.471
time_it { (1..100000).map {[]} }
0.471
time_it { Array.new(100000).map! {[]} }
0.351
time_it { Array.new(100000).map! {[]} }
0.361


Using map! seems the fastest way, thanks for the tip!

-- Christian