From: "Hal E. Fulton" <hal9000@...>
Date: 2003-06-19T08:31:31+09:00
Subject: Re: question on blocks and iterators

----- Original Message -----
From: "Markus Jais" <info@mjais.de>
Newsgroups: comp.lang.ruby
To: "ruby-talk ML" <ruby-talk@ruby-lang.org>
Sent: Wednesday, June 18, 2003 6:18 PM
Subject: question on blocks and iterators


> hello
>
>
> at the end is a sample code
> this does not work as I want. I want to use each_if
> to yield only the elements that support a certain criteria and then
> do something with this elements. but
> here the output is:
>
> ../bl.rb
> e: 5
> e: 8
> e: 9
> 2
> 4
> 5
> 8
> 9
>
> I do not want the numbers 2 and 4 to be printed
>
> I could save the elements in an array and return it but I was wondering if
> there is another possibility

A couple of minor changes (see comments) and this works:

class Array

    def each_if(b)             # no &
        each do |e|
            if b.call(e)
                print "e: ", e, "\n"
                yield e
            end
        end
    end

end


a = [2, 4, 5, 8, 9]

a.each_if(proc { |x| x > 4 }) { |e| puts e }
# one block above is passed as a param

But you could also simply do

a.select {|x| x>4 }.each {|e| puts e}

Couldn't you? The print is just for debugging, right?

Hal