From: jweirich@...
Date: 2001-06-16T03:11:54+09:00
Subject: [ruby-talk:16502] Playing with Ruby Syntax (was: Initial thoughts about Ruby From a Smalltalk Programmer)

    Michael> Hi Everyone, I have to say I'm utterly fascinated by Ruby
    Michael> and I'm really getting in to the spirit of it.

Hi Michael.  Glad you've been enjoying Ruby.

    Michael> Procs, Blocks - a confusion. [...] One of the most
    Michael> comment extensions to Smalltalk that you might find is
    Michael> this:
    Michael>     detect: detectBlock ifFound: foundBlock ifNone: noneBlock

Yes, I agree that I have occasionally wished for the ability to easily
pass multiple blocks to a method.  However, I have found that this
limitation is not too onerous.

Here's some ideas ...

Add the following to Kernel and NilClass ...

    module Kernel
      def if_found
        yield self
        self
      end
      def if_not_found
        self
      end
    end

    class NilClass
      def if_found
        nil
      end
      def if_not_found
        yield self
        nil
      end
    end

Now you can write ...

    [1,2,3].detect { |e|
      e > 2
    }.if_found { |e|
      puts "Found #{e}"
    }.if_not_found {
      puts "Not Found"
    }

There's some minor differences between the above and the Smalltalk
version.  (1) there is some confusion between detecting "nil" and not
finding a match, and (2) I suspect the Smalltalk version returns the
value of the found/not_found block, the above returns the found item.

Although hacking Kernel and NilClass is kinda fun, I probably wouldn't
do it in real life.  I think the following code (using straight Ruby
out of the box) is still the most readable ...

    if item = [1,2,3].detect {|e| e>2}
      puts "Found #{item}"
    else
      puts "Not Found"
    end

-- 
-- Jim Weirich