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Comment by thebigshane | Hacker News Reader

Related: ITA Software's Carl de Marcken discussing their use of Common Lisp for Orbitz from 2001 with a 2002 update.

Snippet:

  ITA Software is slowly replacing the industry's hardware 
  and software with Common Lisp code running on Linux PCs, 
  that uses relatively involved algorithms that show off 
  our academic CS background.

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Yes, it looks like (besides the leftover "ITA" comment in the guide!) that this is simply the ITA guidelines. From Carl's remarks, you can tell that ITA is not a 'normal' Lisp program. Most Lisp programs do not preallocate ~5K of data structures and fail-fast if they exceed that, for example.

Compare to the more conventional Norvig style guide (who is also of course at Google today, coincidentally): http://www.cs.umd.edu/~nau/cmsc421/norvig-lisp-style.pdf (PDF)

ITA actually has two large Lisp systems. One of them is the insanely optimized fare search system (QPX) that does all the crazy things described in the link. The other is the airline reservation system which is a much more conventionally coded Lisp system.

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