From: Dave Anderson <anderson@...>
Date: 2009-11-01T06:50:13+09:00
Subject: Re: In-place parameter modification

Rick Denatale wrote:
...
> Objects are instances of classes, and typically have state, in some
> cases like Fixnums the only state is really the object's identity, and
> such objects are immutable, if two such objects have different state,
> then they MUST be different objects.  There is only one 1 object and
> one 5 object.  Symbols are similar in that there is only one instance
> of symbol with a particular value.

Thanks for the fascinating and valuable insights, Rick. I didn't realize 
what a can of worms I was opening here. And it's nice to know that 
someone here remembers Fortran II, although that might make you a good 
candidate for a Men-In-Black neurolizer. ;-) As an old hand at C++, this 
variable/value/type stuff is a very worthwhile lesson.

One practical thing I can draw out of this is the difference between 
these two functions:

  def X_1( str )
    str[0] = 'X'
  end

  def X_2( str )
     str = 'X' + str[ 1..-1 ]
  end

The X_1 function alters the passed-in object in place, while the X_2 
function modifies a local copy. I don't recall reading this in the 
literature anywhere.
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