
lex_le(+List1, +List2)

   List1 is lexicographically less or equal to List2

Arguments
   List1               List of integers or domain variables
   List2               List of integers or domain variables

Type
   library(fd_global_gac)

Description
    	Imposes a lexicographic ordering between the two lists. 
	I.e. either is the first element of List1 strictly smaller
	than the first element of List2, or the first elements are
	equal and the lexicographic order holds between the two list
	tails. A non-existing element (i.e. when the end of list is 
        reached)is strictly smaller than any existing element.

    This is currently a prototype -- the constraint has not been tested
    very extensively and little effort has been spent to optimise performance.
    We welcome any feedback on using this constraint.

        This constraint is known as lex_lesseq in the global constraint
        catalog. The implementation here maintains generalised arc
        consistency and uses the algorithm described in:
        Z. Kiziltan, 'Symmetry Breaking Ordering Constraints, Ph.D thesis,
        Uppsala University, 2004.



