Dear Forum,
This is to annonunce the availability of a function to
check if a given graph is a line graph, and if yes, then
to actually construct such a graph.
The functions to perfom this have been deposited in
http://www-gap.dcs.st-and.ac.uk/~gap/Info/deposit.html
file "invling.g"

#########################################################################
#                         invling.g
#                               Copyright 1996-1997 D.V.Pasechnik
#                                                   SSOR/TWI, TU Delft
#                                                   Mekelweg 4
#                                                   2628 CD Delft
#                                                   The Netherlands
#                                      e-mail: d.pasechnik@twi.tudelft.nl
#########################################################################
# it comes "as is" - no warranty whatsoever.
#########################################################################
#
# the function InverseLineGraph(G)
#
# constructs the original graph V for a given
# line graph G, or returns false if G is not a line graph.
# G is assumed to be connected.
# V.names are the cliques of G chosen as vertices of V.
#
# After [Leh] P.Lehot, J. of ACM 21(1974) pp 569-575
#
# GRAPE is required.
#                               

Hope it might be useful.
Please don't try it on very large graphs, as it does not
use the automorphism group to make computations faster
(contrary to the general GRAPE phylosophy :-( )

Regards,
Dima
d.pasechnik@twi.tudelft.nl

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