Forum: Ruby hand over block to a submethod

hi @ all,

lets assume I have two methods in class Func

class Func

  def self.mean(array)
    return 0 if(array.size == 0)
    if(block_given?)
      return array.map{|x| yield(x)}.sum.to_f / array.size
    end
    return array.sum.to_f / array.size
  end



  def self.variance(array)
    return 0 if array.size == 0
    avr = Func.mean(array) #HOW TO HAND OVER A BLOCK???

    if(block_given?)
      return array.map { |i| (yield(i) - avr)**2 }.sum / array.size
    end
    return array.map { |i| (i - avr)**2 }.sum / array.size

  end

end


my problem is, that i have to hand over the block given to variance to
the mean method. is this possible and if yes how?

thanks in advance

greets bernhard

On Tue, Sep 11, 2012 at 12:31 PM, bernhard stoecker
<lists@ruby-forum.com> wrote:
>     end
>       return array.map { |i| (yield(i) - avr)**2 }.sum / array.size
>
> thanks in advance
>
> greets bernhard
>
> --
> Posted via http://www.ruby-forum.com/.
>

1.9.2p290 :001 > def test
1.9.2p290 :002?>   if block_given?
1.9.2p290 :003?>     puts "I have a block"
1.9.2p290 :004?>     yield
1.9.2p290 :005?>     else
1.9.2p290 :006 >       puts "no block"
1.9.2p290 :007?>     end
1.9.2p290 :008?>   end
 => nil
1.9.2p290 :011 > def other &blk
1.9.2p290 :012?>   puts "passing block"
1.9.2p290 :013?>   test &blk
1.9.2p290 :014?>   end
 => nil
1.9.2p290 :015 > other
passing block
no block
 => nil
1.9.2p290 :018 > other {puts "I'm the block"}
passing block
I have a block
I'm the block
 => nil

Jesus.

On Tue, Sep 11, 2012 at 12:31 PM, bernhard stoecker
<lists@ruby-forum.com> wrote:
> my problem is, that i have to hand over the block given to variance to
> the mean method. is this possible and if yes how?

You can reference the block passed to the current method with & and
also use that notation to forward it to another method:

def m1(a,b,c,d, &bl)
  m2(x, y, z, &bl)
end

def m2
  yield 1
end

Kind regards

robert

cool! thanks to you guys