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Re: [Axiom-developer] lispdoc

From: Kai Kaminski
Subject: Re: [Axiom-developer] lispdoc
Date: Wed, 16 May 2007 12:18:44 +0200

On May 16, 2007, at 11:20 AM, Martin Rubey wrote:

Ralf Hemmecke <address@hidden> writes:

see <>

I think that won't help me much. But could someone tell me about a few
conventions used in naming identifiers.
A quick overview of the common conventions (and some not so common ones) can be found at

I already know that |blah| keeps blah from being capitalized, but are the bars
part of the identifier?


When do people use identifiers that are surrounded by *, for example


The stars are only a convention, as you noticed already.

A special variable is dynamically scoped - as opposed to the usual lexical scoping in lisp. It is introduced via (defvar *this-is-a-special- variable*)
Or (defparameter *foo* ...). There is a subtle difference, which you probably don't care for, unless you develop your Lisp in an interactive way, which is somewhat difficult with the Axiom sources.

Think of a special variable as a global variable.

What about a colon in front of an identifier? For example,
(array-element-type (make-array 10 :element-type 'character))

As far as I know this is also a convention, namely for keyword arguments.
This isn't quite correct. A symbol that starts with a colon is always interned in the KEYWORD package, rather than the current package. Keyword symbols are used for keyword arguments in functions:

(defun foo (bar &key baz (bam 3))

(foo 3 :bam 7 :baz 9)

You couldn't write (foo 3 bam 7 baz 9) instead, hence it is not a convention in this case.

Keyword symbols are also often used (this is by convention) for things like

(defun find-extremum (list max-or-min)

(find-extremum '(1 2 3 4 5) :max)

Finally keyword symbols are often used in DSLs, like this example from cl-who (

(with-html-output (*http-stream*)
    (:head (:title "My Homepage"))
    (:body (:h1 "hello world"))))


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