From: matz@... (Yukihiro Matsumoto)
Date: 2000-07-07T12:05:06+09:00
Subject: [ruby-talk:03890] Re: Array.uniq! returning nil

Hi,

In message "[ruby-talk:03882] Re: Array.uniq! returning nil"
    on 00/07/06, Aleksi Niemel� <aleksi.niemela@cinnober.com> writes:

|> Basicly one should use copying (non-bang) version of the
|> methods.  
|
|Why's that so? I mean it's a nice policy, but then we should be using it as
|consistenly (and much) as possible. But that's not good for performance.

Well, modifying may cause confusion.  For example,

  a = "my name is matz."
  b = a
  a.sub!(/matz/, "Aleksi")
  puts a
  # prints "my name is Aleksi", it's OK.
  puts b
  # prints "my name is Aleksi", too.  it may be confusing.

Bang methods should be used by the expert who is taking one's risk.
That's why bang-methods contains ugly bang sign.

If I create these methods from scratch, it is possible for me to make
the bang methods always return self.  But CHANGING behavior will crash
fair amount of programs.  Only options I can think of are:

  (a) introduce new methods (but not gsub!? please)
  (b) introduce additional optional argument (as Hugh proposed in
      [ruby-talk:03863])

|I can see:
|
|  a = ["fo", "ha"].collect do |txt| txt+"r" end
|
|should have been (forced and) coded as
|
|  addR = proc do |txt| txt+"r" end
|  a = ["fo", "ha"].collect(addR)
|
|In the latter example the self-modifying part is splitted.

This chunk of code does not contain self-modifying part.

|Well, my strongest argument is yet to come. If the difference between method
|and method! would be just the fact the latter modifies in-place, it'd be:
|1) easy to learn
|2) easy to remember
|3) and most of all, very easy to make performance changes to the existing
|   code

If bang-methods does not have nasty (well, kinda) side-effect, I'd
love to make them default (non-bang) to enhance total performance.
But sadly we have to choose either performance or side-effect.  Only
thing I can do is put the warning sign (both name and behavior) to
tell them it's relatively (and slightly) danger.

							matz.