From: Paul Brannan <pbrannan@...>
Date: 2002-04-23T05:44:32+09:00
Subject: Re: Ruby as Smalltalk

Oops, a small bug in the code I posted produces:

  p false.ifFalse { true }.ifTrue { 42 }.endIf #=> 42

The following should fix it:

  class Object
    class Invalid; end
    def ifTrue(x=Invalid); IfProxy.new(yield, realSelf(x)); end
    def ifFalse(x=Invalid); realSelf(x); end
    def endIf; self; end
    def realSelf(x); (x == Invalid) ? self : x; end
  end
  
  class FalseClass
    def ifTrue(x=Invalid); realSelf(x); end
    def ifFalse(x=Invalid); IfProxy.new(yield, realSelf(x)); end
  end
  
  class NilClass
    def ifTrue(x=Invalid); realSelf(x); end
    def ifFalse(x=Invalid); IfProxy.new(yield, realSelf(x)); end
  end
  
  class IfProxy
    def initialize(x, t); @x = x; @t = t; end
    def ifTrue(x=Invalid, &b); @t.ifTrue(@x, &b); end
    def ifFalse(x=Invalid, &b); @t.ifFalse(@x, &b); end
    def endIf; @x; end
  end

(Unfortunately, it's not quite the same as the real if/then/else/end,
since it doesn't return nil if the condition is false and you don't
supply an else).

Would anyone care to golf with this?

Paul