Subject: Re: quest for pass-by-reference semantics in CL
From: Erik Naggum <>
Date: Thu, 02 May 2002 16:51:17 GMT
Newsgroups: comp.lang.lisp
Message-ID: <>

* Frode Vatvedt Fjeld <>
| Aren't you just redefining the meaning of pass-by-value here? Is there
| any system that isn't pass-by-value under your definition?

  Look, this is getting annoying.  The reference that is intended in the
  term pass-by-reference is not the value of the variable (storage cell),
  it is the variable (storage cell) itself.  This has been the established
  meaning of these terms basically forever.  You are seriously confused if
  you think pointers as such constitute references.

  There are three very, very common ways to pass arguments to functions:

1 Pass by value: The value of the variable (storage cell) is extracted by
  the caller and passed to the callee.  This also means that all arguments
  to a function are just values and a function call can just evaluate all
  arguments in order and pass the values to the callee.  This is precisely
  what Common Lisp specifies.

2 Pass by reference: The variable (storage cell) is passed to the callee,
  which can read or write to it.  This means that you cannot call a
  function with the value of another function call without storing it in a
  variable.  Fortran has _traditionally_ been pass-by-reference.  Ada has
  out parameters.  C++ has references (coincidence? not!).

3 Pass by name: The expression itself is passed to the callee, which will
  re-evaluate it with the values of subexpressions captured in the call.
  (They actually pass closures much like I and Joe and Pierre offered with
  the setter/reference macro.)  This is what Algol and Simula can do.

  This is (or should have been) CS 101 material.  Please just learn it and
  avoid confusing others who might have no education at all and are likely
  to listen to bogosities.  Having to clean up after such confusions is
  both annoying and wasteful when you could have avoided the "information
  pollution" in the first place.
  In a fight against something, the fight has value, victory has none.
  In a fight for something, the fight is a loss, victory merely relief.

  70 percent of American adults do not understand the scientific process.