From: William James <w_a_x_man@...>
Date: 2006-08-02T18:25:09+09:00
Subject: Re: golfing Eratosthenes

William James wrote:
> Daniel Baird wrote:
> > On 8/2/06, Daniel Baird <danielbaird@gmail.com> wrote:
> > > Hi all,
> > >
> > > I've been golfing around with the sieve of Eratosthenes.  Here's what
> > > I've got so far:
> > >
> > > a=(2..100).to_a;p a.each{|c|a.map!{|d|c&&d&&c<d&&d%c==0?nil:d}}.compact
> > >
> > > It's already under 80 chars, but I'd still love to remove the
> > > definition of the array a, and do the whole thing with no semicolons.
> > > Any suggestions?
> > >
> >
> > Improvement:
> >
> > a=(2..100).to_a;p a.each{|c|a.reject!{|d|c<d&&d%c==0}}
> >
> > .swapped to reject, and now I don't have to test for c and d being
> > nil, or do the final  compact.  Seems ok even though I'm editing the
> > array I'm looping through..
>
> p (2..100).inject([]){|a,n|a.any?{|i|n%i==0}?a:a<<n}
  p (2..100).inject([]){|a,n|a.any?{|i|n%i<1}?a:a<<n}