X-Git-Url: https://svn.cri.ensmp.fr/git/linpy.git/blobdiff_plain/ddefc755b0637b08a0a2788be3a0678b52942f5b..6d08d8c0a84c1ffa31f5eb16e33b340727f46175:/linpy/polyhedra.py?ds=sidebyside diff --git a/linpy/polyhedra.py b/linpy/polyhedra.py index bfc7efe..f802151 100644 --- a/linpy/polyhedra.py +++ b/linpy/polyhedra.py @@ -37,8 +37,9 @@ __all__ = [ class Polyhedron(Domain): """ A convex polyhedron (or simply "polyhedron") is the space defined by a - system of linear equalities and inequalities. This space can be - unbounded. + system of linear equalities and inequalities. This space can be unbounded. A + Z-polyhedron (simply called "polyhedron" in LinPy) is the set of integer + points in a convex polyhedron. """ __slots__ = ( @@ -56,28 +57,31 @@ class Polyhedron(Domain): 0 <= x <= 2, 0 <= y <= 2 can be constructed with: >>> x, y = symbols('x y') - >>> square = Polyhedron([], [x, 2 - x, y, 2 - y]) + >>> square1 = Polyhedron([], [x, 2 - x, y, 2 - y]) + >>> square1 + And(0 <= x, x <= 2, 0 <= y, y <= 2) It may be easier to use comparison operators LinExpr.__lt__(), LinExpr.__le__(), LinExpr.__ge__(), LinExpr.__gt__(), or functions Lt(), Le(), Eq(), Ge() and Gt(), using one of the following instructions: >>> x, y = symbols('x y') - >>> square = (0 <= x) & (x <= 2) & (0 <= y) & (y <= 2) - >>> square = Le(0, x, 2) & Le(0, y, 2) + >>> square1 = (0 <= x) & (x <= 2) & (0 <= y) & (y <= 2) + >>> square1 = Le(0, x, 2) & Le(0, y, 2) It is also possible to build a polyhedron from a string. - >>> square = Polyhedron('0 <= x <= 2, 0 <= y <= 2') + >>> square1 = Polyhedron('0 <= x <= 2, 0 <= y <= 2') Finally, a polyhedron can be constructed from a GeometricObject instance, calling the GeometricObject.aspolyedron() method. This way, it is possible to compute the polyhedral hull of a Domain instance, i.e., the convex hull of two polyhedra: - >>> square = Polyhedron('0 <= x <= 2, 0 <= y <= 2') - >>> square2 = Polyhedron('2 <= x <= 4, 2 <= y <= 4') - >>> Polyhedron(square | square2) + >>> square1 = Polyhedron('0 <= x <= 2, 0 <= y <= 2') + >>> square2 = Polyhedron('1 <= x <= 3, 1 <= y <= 3') + >>> Polyhedron(square1 | square2) + And(0 <= x, 0 <= y, x <= y + 2, y <= x + 2, x <= 3, y <= 3) """ if isinstance(equalities, str): if inequalities is not None: