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D.13.2.9 cycleLength

Procedure from library polymake.lib (see polymake_lib).

Usage:
cycleLength(boundary,interior); list boundary, intvec interior

Assume:
boundary is a list of integer vectors describing a cycle in some convex lattice polygon around the lattice point interior ordered clock wise

Return:
string, the cycle length of the corresponding cycle in the dual tropical curve

Example:
 
LIB "polymake.lib";
==> Welcome to polymake version
==> Copyright (c) 1997-2015
==> Ewgenij Gawrilow, Michael Joswig (TU Darmstadt)
==> http://www.polymake.org
// the integer vectors in boundary are lattice points on the boundary
// of a convex lattice polygon in the plane
list boundary=intvec(0,0),intvec(0,1),intvec(0,2),intvec(2,2),
intvec(2,1),intvec(2,0);
// interior is a lattice point in the interior of this lattice polygon
intvec interior=1,1;
// compute the general cycle length of a cycle of the corresponding cycle
// in the dual tropical curve, note that (0,1) and (2,1) do not contribute
cycleLength(boundary,interior);
==> -4*u11+u00+u02+u22+u20