In response to a challenge, I decided to actual solve the problem. Here it is. The lyrics are here: http://www.99-bottles-of-beer.net/lyrics.html
ten := {{ n:=0 },{ n:=1 },{ n:=2 },{ n:=3 },{ n:=4 },{ n:=5 },{ n:=6 },{ n:=7 },{ n:=8 },{ n:=9 }}
hundred := (ten join ten[{nn:=n}]) [ {neg := -10*nn-n,nnn := 10*nn+n}] [nnn>0]
line1 := hundred [{ neg, text := nnn || " bottle" || if(nnn=1,"","s") || " of beer on the wall, " ||
nnn || " bottle" || if(nnn=1,"","s") || " of beer."}]
line2 := hundred [{ neg:=neg+0.5, text := "Take one down and pass it around, " || (nnn-1) || " bottle" ||
if(nnn=2,"","s") || " of beer on the wall."}]
line3 := "No more bottles of beer on the wall, no more bottles of beer."
line4 := "Go to the store and buy some more, 99 bottles of beer on the wall."
(line1 union line2) [$] [{text}] union {{text:=line3},{text:=line4}}
The first two lines just generate the sequence. Later there will be a better way to do that. The 4 lines of text are dictated by the song lyrics. Most of the program is fiddly details to precisely match the song lyrics as published, and get the lines in the right order. The end result is a relation containing the song lyrics in the correct order, which is then simply printed.
I found this quite a fascinating exercise. I had to implement IF(,,) but I think the only other control structure needed is user-defined recursive functions. The result is a programming paradigm quite unlike any that I’m familiar with, and surprisingly powerful. And weird.