Subject: Re: how to validate input?
From: Erik Naggum <>
Date: 2000/04/25
Newsgroups: comp.lang.lisp
Message-ID: <>

* Fernando <spamers@must.die>
| Do you know why this was left out of the standard?  Comming
| from a Scheme background, it sounds a bit weird to me...

  coming from a Scheme background, it should be easy for you to explain why
  Scheme needs it so badly and what implementation costs are associated
  with this requirement.  then you should consider whether there are any
  needs in Common Lisp that are unfulfilled without it, like there would be
  in Scheme without it, and whether they are worth the costs.  please note
  that proper tail recursion is closely related to first-class continuations.

  incidentally, it is never productive to ask why things are "left out" of
  a standard unless you know that that was what happened.  tail recursion
  is simply a non-issue in most languages, and where it matters, it had
  been a choice of the compiler writers and optimization settings, not a
  hard requirement in a standard.

  that said, one reason to leave out random "good ideas" from a standard is
  that requiring something that nobody needs in doesn't mean people will
  abide by it, but it does mean they will have to start to ignore parts of
  the standard for _good_ reasons.  this is very, very bad when it happens.