pairwise concatenation

pairwise concatenation

[haahr]

well, i offered a prize two weeks ago for the best use of pairwise  
concatenation in rc.  i got exactly one response, which noted that simple  
concatenation of a^b was really the pairwise concatenation of two n-element  
lists, where n==1; the author of this response said that it was not an  
entry into the contest, so i won't have to be picky and try to disqualify  
the entry as against the spirit of the rules.

therefore, i am extending my offer, and upping the prize.  to the first  
person who sends me a real, non-trivial use of rc's pairwise concatenation  
(that is, concatenation of two n-element lists, for n > 1), i will give  
either

	a shrink wrapped, licensed copy of adobe illustrator for the
	platform of your choice. (mac, pc, and next are available now;
	many x/dps versions to be available within the next year.)

		or

	a cash prize of US$100.

(winner's choice.)

this offer is open ended; the first example that Byron and i can agree on  
as being a potential real-world use of pairwise concatenation will win.   
examples which are constructed solely for the purpose of entering them into  
this contest are acceptable, but you have to convince me that someone would  
have a good reason for using the construct in real life.

paul