/frames 16 def 

%include /u/rs/book3/pslib/tools.ps
%include /u/rs/book3/pslib/example.ps

/bubblesort
 { 1 1 N 1 sub { dup 
                N 1 sub exch -1 exch 1 add {dup 1 sub compareswap} for 
                N 1 sub SUBFILEx
              } for
 } def

LL RR SUBFILE
bubblesort 
LL RR SUBFILE

----------------------------
T 147pt Bubble sorting example

Large keys percolate over to the left in bubble sort.  Each key is
exchanged with the one on its right until a large one is encountered.
In particular, the largest key makes it to the end of the file on the
first pass: First the {\F S} moves to the {\F T}, then the {\F T} to
the {\F X}, then the {\F X} to the end of the file. Then the next
largest makes it to its final position on the second pass, etc.