Function CAR in LISP program returns the first element in a list.
(car '(a b c d)) Returns a
Function CDR would return everything but the first element in a list.
(cdr '(a b c d)) returns (b c d)
There are of course many variations of this.
(cadr '(a b c d)) Returns b
Working from the inside out is the same as (car (cdr '(a b c d)))
I would insist to reintroduce "Lot of Insane and Stupid Parenthesis" somewhere this is a famous joke and has also its place in Wikipedia. Ericd 20:27 Apr 14, 2003 (UTC)
It is in there. Paragraph 2 of "Syntax". It's "Lots of Irritating Superfluous Parentheses", btw (sometimes also "Lots of Isolated Silly Parenthesis".) -- CYD
I propose that this page should be entitled Lisp programming language for two reasons: First, the spelling "LISP" (in capitals) does not seem to be used among current practitioners of the language. (See for instance the newsgroup comp.lang.lisp and the work of Paul Graham.) Second, this will bring it in line with the other pages of the form "Name programming language" while preserving distinction from the word for the speech impediment. --FOo 00:40 7 Jun 2003 (UTC)
- I don't think we need programming language. In fact, many article has no programming language suffix. Take Fortran, C Plus Plus and so on. -- Taku 00:47 7 Jun 2003 (UTC)
- Hmm. LISP is its proper name, and since it's an acronym, it seems to me more appropriate to keep it in caps. Perl, for example, is in lowercase, since it was backronymed, and is not really supposed to be in caps. COBOL remains uppercase, without the "programming language" suffix. Fortran has no suffix either. Convention seems to say leave it as is... -- Wapcaplet 00:58 7 Jun 2003 (UTC)
- "LISP" is long-obsolete; look at 2nd edition Common Lisp the Language from 1990 for instance, it's always spelled "Lisp", in contrast to 1st ed., which used small caps. I'd personally prefer Lisp (programming language) because someday we might have spiffy software that filters ()-disambiguators in article headings and such, but Lisp programming language is OK too. Stan 01:12 7 Jun 2003 (UTC)
- There already is such a thing: the magic piping trick. For example, typing [[spin (physics)|]] gives you spin. Unlike the names of other programming languages, Lisp has another meaning, i.e. a speech defect. Therefore, the article should be named Lisp (programming language). -- CYD
- Since there is an obvious ambiguity, I have no objection to rename this to Lisp programming language. Please don't use (programming language) because that style is not used usually. -- Taku 01:53 7 Jun 2003 (UTC)
According to the convension about naming programming language, we don't put pre-diambiguation programming language. It is debatable but is an agreement that seems reached. I am not sure which one LISP or Lisp. To me LISP sounds rather antiquated but I am not sure. -- Taku 01:19 7 Jun 2003 (UTC)
- To me, spelling it "LISP" reeks of either a botched transliteration from small-caps (as with "UNIX", see the jargon file) or a usage on all-caps terminals or filesystems. Bleah. I recognize the "Foo programming language" (rather than "Foo (programming language)") convention for languages whose names have another meaning (like Python, C, and Lisp, and unlike Fortran) --FOo 03:55 7 Jun 2003 (UTC)
I agree that this should be moved to "Lisp programming language". The lower case form is much more common. -- Minesweeper 17:33 7 Jun 2003 (UTC)
Which variants of Lisp have native Unicode support? --Hirzel
- http://www.cliki.net/Unicode%20and%20Lisp -- Taku 02:17 12 Jun 2003 (UTC)
- Thank you for the answer!
The article says:
A minimal Lisp needs just a few functions implemented in C or machine language.
* car * cdr * cons * quote * eq * cond * a mechanism to define functions
Is there an open source C (or Pascal, Basic or whatever implementation) which shows how this is done? A lisp version is found here (use link McCarthy's original implemenation) --Hirzel 08:08 1 Jul 2003 (UTC)
- Is "cond" really necessary? I think if you define "true" and "false" appropriately, you could implement cond. Also, is it possible to implement gt and lt if you only have eq?
- Yes. You need some means of making a branch, or conditional statement -- either cond or if can provide this. As for eq, it is not used for arithmetical equality, but rather for determining whether two symbols are the same. Arithmetic doesn't enter into it -- this is a minimal set of operations for list and program-code manipulation, not for arithmetic. Anyhow, arithmetic can be implemented (slowly!) in terms of lists or functions, as by using a W-representation or Church integers. --FOo 15:04, 7 Aug 2003 (UTC)
- Forgive my notation, but True can be defined as "\ x . x" and False as "\ x ." where "\" is lambda. Then cond would be unnecessary because True and False would take care of it. Of course, if you're using eager evaluation, this isn't quite true, because "(False foo)" will still evaluate foo (which doesn't matter if it's referentially transparent).P3d0 15:15, 7 Aug 2003 (UTC)
- It wouldn't be Lisp anymore then; "cond" is the fundamental conditional construct shared by all Lisp versions. Stan 16:10, 7 Aug 2003 (UTC)
- Have a little imagination. If I can get the effect of "cond" using lambda calculus, I'm sure someone smarter than me can get the syntax in a similar fashion. Lambda calculus is Turing-equivalent on its own, and doesn't need a "cond" primitive to get that way. --P3d0 11:27, 8 Aug 2003 (UTC)
- This is an article on Lisp, not alternate possibilities for Lisp-like languages. The purpose of the encyclopedia is to describe things as they are, not as they could be, unless the hypothetical somehow elucidates. For instance, one could make a comment that "cond is not strictly necessary under some evaluation regimes" or some such, and in fact there is an interesting little bit of history about how these particular primitives came to be chosen. Stan 13:45, 8 Aug 2003 (UTC)
- It wouldn't be Lisp since Lisp cond and if are defined as having conditional evaluation of arguments. For that matter, it should be theoretically possible to make a Lisp system solely out of NAND gates (including flip-flops for memory), but that does not mean that NAND constitutes a Lisp system. --FOo 14:03, 8 Aug 2003 (UTC)
- I'm sorry, I must not understand what you mean by "minimal" then. If I can implement cond using elements that are already in the language, then I don't need cond, right? I'm almost certain I could define cond in terms of "a mechanism to define functions" (ie. lambda calculus), making it redundant in a minimal Lisp. If you really don't believe me, I'll take the time to actually do this, though I'm not a lambda calculus expert, so it will take some effort. If it's just the concept of "minimal" that we disagree on, then that may be easier to resolve. --P3d0 15:15, 8 Aug 2003 (UTC)
- If you dropped any of these functions, a Lisp programmer would say "this isn't Lisp anymore", so "minimal" is the right word. It doesn't matter what lambda calculus is capable of (by that standard, car/cdr/cons aren't necessary either), because this is about Lisp the language as it is normally understood. If you want to write about some other language that looks like Lisp but has fewer primitives, publish an article about it in Dr. Dobbs and then we'll reference it here. Stan 15:31, 8 Aug 2003 (UTC)
- Ok Stan, I think I see where you are coming from. Whether cond is defined by lambda calculus, or is provided as a primitive, the fact remains that it must be defined somehow in any language that claims to be Lisp. So I yield. :-)
- Incidentally, CYD, do you think a Turing machine could implement an interpreter for cond, including the syntax? If so, lambda calculus can do it too, because lambda calculus is Turing-equivalent. --P3d0 03:48, 9 Aug 2003 (UTC)
- My point is that it is probably syntactically impossible, since cond uses some special syntactic rules that are treated specially by the Lisp interpreter. In other words, you'd have a problem getting the input into your "Turing machine" without encountering an interpreter error. Of course, I'd be happy to agree that you were correct if you can show us how to implement cond with lambda. -- CYD