Subject: Re: Destructive Side Effects
From: Erik Naggum <>
Date: Sat, 17 Nov 2001 23:10:01 GMT
Newsgroups: comp.lang.lisp
Message-ID: <>

* "David McClain" <>
| Actually, this is one of the surprising things about REMF that caught my
| attention.  You are correct that most often destructive operations in
| Lisp operate in a functional manner... except for REMF (and no doubt a
| few others...)

  Why this _completely_ irrelevant hangup?  If properties were implemented
  with a hashtable, would you complain that remhash does not return a new
  hashtable instead of modifying the one you passed, too?  Oh, no, now you
  will complain about remhash.  What have I _done_?  Now Common Lisp will
  crumble because property lists _and_ hashtables are mutable objects.

  Have you noticed that when you intern a symbol in a package, you do not
  get a new package?  Or that when you read a character off a stream, you
  do not geta new stream?  Or that when you write a character to a stream,
  which modifies a file on disk, you do not get a new disk?

  That you think REMF is "destructive" is only because you are looking at
  things at too low a level for your own good and abuse the implementation
  detail that it is a list, which is again because you have not quite
  figured out how to get what you want from the language.  Even in your
  "side-effect-freeness" you actually modify memory cells in your computer,
  you know, but you would most probably argue that this is irrelevant to
  the side-effect-freeness nature of your programming language, right?
  Well, side-effect-free is actually _nothing_ but perspective.

  You only have a problem understanding how (Common) Lisp works.  Once you
  get that understanding, you will either be the type who gripes about some
  feature you do not like for the rest of your life, or you will be the
  type who can make a more informed choice about which language you want to
  spend your time on, and then leave the rest alone.  I really wonder what
  it is with Common Lisp that makes people first discover the language and
  then start to make up so many stupid problems with it just because they
  have some serious personality problems.  I mean, _none_ of the standard
  conditionals are usable by some dude, and now remf is "destructive" and
  that by itself ticks some other troll off.  Sheesh.

  Norway is now run by a priest from the fundamentalist Christian People's
  Party, the fifth largest party representing one eighth of the electorate.
  Carrying a Swiss Army pocket knife in Oslo, Norway, is a criminal offense.