##
## It contains the allocation to the variable coxeter_lcorder of the 
## order relation on the left cells, inherited from the preorder relation
## <=_L on the group. What we output is the hasse diagram of this ordering
## (or rather of the dual ordering) : for each cell, we print the list
## of cells that lie immediately above it (recall that {e} is the *largest*
## element in the left cell ordering.) As always, cells are represented
## by their index number in the list which is output by lcells; in this
## file, we produce the abstract ordering on the integers {1, ..., N}, where
## N is the number of left cells.
##
## Note that the enumeration ordering we use on cells is not compatible with
## the (reversed) left cell ordering, in the sense that edges in our hasse
## diagram do not always go to elements with a smaller index. It would be
## possible to re-sort the cells so that this would be true, but we have
## refrained from doing that for the sake of consistency.
##
