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Neat TYPEP Trick #
hacking, May 15th 2012

How do you test if an object is a cons that has the desired symbol in the car?

(typep x '(cons (eql :foo)))

Sure,

(and (consp x) (eq :foo (car x)))

is essentially just as short...

I still find cons types neat, even if they're a nightmare when it comes to type derivation, but that's a different matter. Some nightmares aren't all bad.

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Nikodemus Siivola, <nikodemus@random-state.net>
Vaasankatu 6 C 49, 00500 Helsinki, Finland
+358 44 2727 526

Why Common Lisp?

Read all about the features of Common Lisp. Then get your bearings sorted out by having a look at the Nikodemus' Common Lisp FAQ.

Projects

I'm involved in more open source projects than I care to count. Here are the ones I think need more googlejuice.

Alexandria is a popular Common Lisp utility library. Depending on it doesn't make life of your users any harder: they are likely to already use code that depends on it.
Esrap is a packrat parser for Common Lisp. It's mostly feature complete, though the cache is currently a bottleneck for large parsing jobs.
Linedit is a readline-style line-editor for Common Lisp. It's not under active development, but it is expected to work and still maintained.
Osicat is a lightweight operating system interface library for Common Lisp. I think it seriously needs more publicity.
Pileup is a portable, performant, and thread-safe binary heap for Common Lisp. Not rocket science, but does the job.
sb-cga is a computer graphics algebra library for SBCL. Works fine already, and there's a CCL port too, but there are still things I want to improve.
sb-cpu-affinity is an interface to the Linux CPU affinity masks for SBCL. If someone needs this on another implementation, porting should actually not be very hard.
sb-daemon provides process daemonization for SBCL. Destined to become on SBCL contrib Real Soon Now.
SBCL is an open source Common Lisp compiler capable of generating code on par with C. Most of the time it is within a small factor of C, but if you know what you're doing then comparison to C is quite reasonable. I'm one of the current developers and maintainers.
Screamer provides a nondeterministic choice-point operator, a backtracking mechanism, and a forward propagation facility for Common Lisp. It was originally developed by by Jeffrey Mark Siskind and David Allen McAllester. It is very nifty. I maintain a copy under MIT-license.
Slime is a Superior Lisp Interaction Mode for Emacs. If you're using Common Lisp, you really want to use Slime as well. I'm a minor contributor, mostly puttering around the SBCL backend, and only occasionally braving the elisp side of the codebase.

Recommendations

If you are looking for lisp libraries, use Quicklisp and look no further.

Life

I practise historical fencing at School of European Swordmanship Helsinki, and keep a separate training diary about that.

...I do other stuff as well, but that's none of your business. :)

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