Peter Siebel - Practical Common Lisp

AspectL is an interesting project insofar as AspectJ, its Java-based predecessor, was written by Gregor Kiczales, one of the designers of Common Lisp's object and metaobject systems. To many Lispers, AspectJ seems like Kiczales's attempt to backport his ideas from Common Lisp into Java. However, Pascal Costanza, the author of AspectL, thinks there are interesting ideas in AOP that could be useful in Common Lisp. Of course, the reason he's able to implement AspectL as a library is because of the incredible flexibility of the Common Lisp Meta Object Protocol Kiczales designed. To implement AspectJ, Kiczales had to write what was essentially a separate compiler that compiles a new language into Java source code. The AspectL project page is at http://common-lisp.net/project/aspectl/.

Or to look at it another, more technically accurate, way, Common Lisp comes with a built-in facility for integrating compilers for embedded languages.

Lisp 1.5 Programmer's Manual (M.I.T. Press, 1962)

Ideas first introduced in Lisp include the if/then/else construct, recursive function calls, dynamic memory allocation, garbage collection, first-class functions, lexical closures, interactive programming, incremental compilation, and dynamic typing.

One of the most commonly repeated myths about Lisp is that it's "dead." While it's true that Common Lisp isn't as widely used as, say, Visual Basic or Java, it seems strange to describe a language that continues to be used for new development and that continues to attract new users as "dead." Some recent Lisp success stories include Paul Graham's Viaweb, which became Yahoo Store when Yahoo bought his company; ITA Software's airfare pricing and shopping system, QPX, used by the online ticket seller Orbitz and others; Naughty Dog's game for the PlayStation 2, Jak and Daxter, which is largely written in a domain-specific Lisp dialect Naughty Dog invented called GOAL, whose compiler is itself written in Common Lisp; and the Roomba, the autonomous robotic vacuum cleaner, whose software is written in L, a downwardly compatible subset of Common Lisp. Perhaps even more telling is the growth of the Common-Lisp.net Web site, which hosts open-source Common Lisp projects, and the number of local Lisp user groups that have sprung up in the past couple of years.

Superior Lisp Interaction Mode for Emacs

If you've had a bad experience with Emacs previously, you should treat Lisp in a Box as an IDE that happens to use an Emacs-like editor as its text editor; there will be no need to become an Emacs guru to program Lisp. It is, however, orders of magnitude more enjoyable to program Lisp with an editor that has some basic Lisp awareness. At a minimum, you'll want an editor that can automatically match ()s for you and knows how to automatically indent Lisp code. Because Emacs is itself largely written in a Lisp dialect, Elisp, it has quite a bit of support for editing Lisp code. Emacs is also deeply embedded into the history of Lisp and the culture of Lisp hackers: the original Emacs and its immediate predecessors, TECMACS and TMACS, were written by Lispers at the Massachusetts Institute of Technology (MIT). The editors on the Lisp Machines were versions of Emacs written entirely in Lisp. The first two Lisp Machine Emacs, following the hacker tradition of recursive acronyms, were EINE and ZWEI, which stood for EINE Is Not Emacs and ZWEI Was EINE Initially. Later ones used a descendant of ZWEI, named, more prosaically, ZMACS.

Practically speaking, there's very little likelihood of the language standard itself being revised—while there are a small handful of warts that folks might like to clean up, the ANSI process isn't amenable to opening an existing standard for minor tweaks, and none of the warts that might be cleaned up actually cause anyone any serious difficulty. The future of Common Lisp standardization is likely to proceed via de facto standards, much like the "standardization" of Perl and Python—as different implementers experiment with application programming interfaces (APIs) and libraries for doing things not specified in the language standard, other implementers may adopt them or people will develop portability libraries to smooth over the differences between implementations for features not specified in the language standard.

Steel Bank Common Lisp

CMU Common Lisp

SBCL forked from CMUCL in order to focus on cleaning up the internals and making it easier to maintain. But the fork has been amiable; bug fixes tend to propagate between the two projects, and there's talk that someday they will merge back together.

The venerable "hello, world" predates even the classic Kernighan and Ritchie C book that played a big role in its popularization. The original "hello, world" seems to have come from Brian Kernighan's "A Tutorial Introduction to the Language B" that was part of the Bell Laboratories Computing Science Technical Report #8: The Programming Language B published in January 1973. (It's available online at http://cm.bell-labs.com/cm/cs/who/dmr/bintro.html.)

These are some other expressions that also print the string "hello, world":

(write-line "hello, world")

or this:

(print "hello, world")

Well, as you'll see when I discuss returning multiple values, it's technically possible to write expressions that evaluate to no value, but even such expressions are treated as returning NILwhen evaluated in a context that expects a value.

I'll discuss in Chapter 4 why the name has been converted to all uppercase.

You could also have entered the definition as two lines at the REPL, as the REPL reads whole expressions, not lines.

SLIME shortcuts aren't part of Common Lisp—they're commands to SLIME.

If for some reason the LOAD doesn't go cleanly, you'll get another error and drop back into the debugger. If this happens, the most likely reason is that Lisp can't find the file, probably because its idea of the current working directory isn't the same as where the file is located. In that case, you can quit the debugger by typing qand then use the SLIME shortcut cdto change Lisp's idea of the current directory—type a comma and then cdwhen prompted for a command and then the name of the directory where hello.lispwas saved.

http://www.flownet.com/gat/jpl-lisp.html

Before I proceed, however, it's crucially important that you forget anything you may know about #define-style "macros" as implemented in the C pre-processor. Lisp macros are a totally different beast.

Using a global variable also has some drawbacks—for instance, you can have only one database at a time. In Chapter 27, with more of the language under your belt, you'll be ready to build a more flexible database. You'll also see, in Chapter 6, how even using a global variable is more flexible in Common Lisp than it may be in other languages.

One of the coolest FORMAT directives is the ~Rdirective. Ever want to know how to say a really big number in English words? Lisp knows. Evaluate this: