Redmine

Hello
Methods permutation and combination are defined for array but it make more sense to define them for enumerable.
Here is sample implementation which for simplicity works only with blocks.

module Enumerable
  def perm(n)
    comb(n){|ary|
      ary.permutation{|p| yield(p)}
    }
  end
  def comb(n,&m)
    ary=[]
    e=to_enum.with_index
    _comb(e,n-1,1.0/0.0,ary,m)
  end

  def _comb(e,n,bound,ary,m)
    e.each{|el,i|
      return if i>=bound
      ary[n]=el
      if n==0
        m.call(ary)
      else
        _comb(e,n-1,i,ary,m)
      end
    }
  end

end
[1,2,4,3,5].comb(2){|a| puts a.inspect}
(1..4).comb(2){|a| puts a.inspect}
(1..4).perm(2){|a| puts a.inspect}