From: Pedro Silva <ei04065@...>
Date: 2008-09-06T08:59:01+09:00
Subject: Request: arguments by reference

Would be possible to include the option to pass arguments by reference
instead of by value?

  def swap(a, b)
    tmp = a
    a = b
    b = a
  end

  a = "A"
  b = "B"
  swap(a, b)
  puts a, b # "A", "B"

Because Ruby passes arguments by value any attribution will change only
the arguments not the variables. My sugestion is to use some way of
indicating that the argument is a reference and that would allow the
above example to work.
I don't know if this will mess things up, but I guess the difference is
only instead of creating a new variable, "tell" the intrepeter to use
the variable passed as argument. But that can break something...

I know the above example can be done like 'a, b = b, a', but this always
obliges to set things directly and never allow to use functions, that,
in my opinion, is a limitation. The actual way forces the programmer to
know if any particular method creates or not a new object. For instance:

  def append_str(str, append)
    str << append
  end

  def add_str(str, add)
    str += add
  end

  a = "A"
  b = "B"

  append_str(a, " + something")
  add_str(b, " + nothing")

  puts a, b # "A + something", "B"

<< operator changes the object itself so a will be changes, += creates a
new object so b won't be changed. Taking into account that Ruby uses
mainly references for each object (fixnum and company are the
exceptions) I hope this would be possible to include.
-- 
Posted via http://www.ruby-forum.com/.