TeX quines

Quine is a program, which outputs its own source code. I wrote several quines in Plain TeX. The shortest one I found is q. (64 characters + banner). IniTeX version: i. Some older attempts: q.1, q.2, q.3, q.4. Here's one which prints itself to the dvi file. It too has an iniTeX variant.

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Unlambda resources

I wrote several interpreters for the wonderful Unlambda programming language by David Madore.

• unl.c: this one is written in C. It is the fastest Unlambda interpreter I know about, and I also tried to make it less buggy than other extant Unlambda interpreters in C. It is accompanied by unlc, a simplistic Unlambda-to-C compiler (written in Perl).
• unl.lisp, unlt.lisp: these are written in Common Lisp. The first one is as simple as possible, it may serve as an inspiration if you want to write an interpreter yourself (in fact, all of my Unlambda interpreters are based on this one). The second one implements a handy debugging extension. It understands new primitive functions “t” and “n”, which behave as “i”, except that `tF evaluates the form F in a tracing mode, while `nF disables tracing during evaluation of F.
• unl.pl: this one is written in Perl, and is not particularly interesting.
• unl.pro: and this one is in Prolog.
• unl.ps: yes, this is an Unlambda interpreter written in PostScript.

I also wrote an Unlambda interpreter in Unlambda, which you can find on the Comprehensive Unlambda Archive Network.

Some Unlambda programs:

• oneliners: cat.unl, tac.unl (this is character-based tac, not line-based)
• ROT13: rot13.unl
• Sierpiński’s triangle: sierp.unl
• von Neumann integers: omega.unl

Finally, eliminate is a lambda elimination tool (written in Perl).