Tutorial
========
+This section a short introduction to some of LinPy's features.
+For a comprehensive description of its functionalities, please consult the :ref:`reference`.
+
+
+.. _tutorial_polyhedra:
+
Polyhedra
---------
>>> square1 = Le(0, x, 2) & Le(0, y, 2)
>>> square1
-And(Ge(x, 0), Ge(-x + 2, 0), Ge(y, 0), Ge(-y + 2, 0))
+And(0 <= x, x <= 2, 0 <= y, y <= 2)
LinPy provides comparison functions :func:`Lt`, :func:`Le`, :func:`Eq`, :func:`Ne`, :func:`Ge` and :func:`Gt` to build constraints, and logical operators :func:`And`, :func:`Or`, :func:`Not` to combine them.
Alternatively, a polyhedron can be built from a string:
>>> square2 = Polyhedron('1 <= x <= 3, 1 <= y <= 3')
>>> square2
-And(Ge(x - 1, 0), Ge(-x + 3, 0), Ge(y - 1, 0), Ge(-y + 3, 0))
+And(1 <= x, x <= 3, 1 <= y, y <= 3)
The usual polyhedral operations are available, including intersection:
->>> inter = square1.intersection(square2)
+>>> inter = square1.intersection(square2) # or square1 & square2
>>> inter
-And(Ge(x - 1, 0), Ge(-x + 2, 0), Ge(y - 1, 0), Ge(-y + 2, 0))
+And(1 <= x, x <= 2, 1 <= y, y <= 2)
convex union:
>>> hull = square1.convex_union(square2)
>>> hull
-And(Ge(x, 0), Ge(y, 0), Ge(-x + y + 2, 0), Ge(x - y + 2, 0), Ge(-x + 3, 0), Ge(-y + 3, 0))
+And(0 <= x, 0 <= y, x <= y + 2, y <= x + 2, x <= 3, y <= 3)
and projection:
->>> square1.project([y])
-And(Ge(x, 0), Ge(-x + 2, 0))
+>>> proj = square1.project([y])
+>>> proj
+And(0 <= x, x <= 2)
Equality and inclusion tests are also provided.
Special values :data:`Empty` and :data:`Universe` represent the empty and universe polyhedra.
False
+.. _tutorial_domains:
+
Domains
-------
An example of domain is the set union (as opposed to convex union) of polyhedra ``square1`` and ``square2``.
The result is a :class:`Domain` object.
->>> union = square1 | square2
+>>> union = square1.union(square2) # or square1 | square2
>>> union
-Or(And(Ge(-x + 2, 0), Ge(x, 0), Ge(-y + 2, 0), Ge(y, 0)), And(Ge(-x + 3, 0), Ge(x - 1, 0), Ge(-y + 3, 0), Ge(y - 1, 0)))
+Or(And(x <= 2, 0 <= x, y <= 2, 0 <= y), And(x <= 3, 1 <= x, y <= 3, 1 <= y))
>>> union <= hull
True
Unlike polyhedra, domains allow exact computation of union, subtraction and complementary operations.
->>> diff = square1 - square2
+>>> diff = square1.difference(square2) # or square1 - square2
>>> diff
-Or(And(Eq(x, 0), Ge(y, 0), Ge(-y + 2, 0)), And(Eq(y, 0), Ge(x - 1, 0), Ge(-x + 2, 0)))
+Or(And(x == 0, 0 <= y, y <= 2), And(y == 0, 1 <= x, x <= 2))
>>> ~square1
-Or(Ge(-x - 1, 0), Ge(x - 3, 0), And(Ge(x, 0), Ge(-x + 2, 0), Ge(-y - 1, 0)), And(Ge(x, 0), Ge(-x + 2, 0), Ge(y - 3, 0)))
+Or(x + 1 <= 0, 3 <= x, And(0 <= x, x <= 2, y + 1 <= 0), And(0 <= x, x <= 2, 3 <= y))
+
+.. _tutorial_plot:
Plotting
--------
.. figure:: images/union.jpg
:align: center
-3D plots are also supported.
+3D plots are also supported:
>>> import matplotlib.pyplot as plt
>>> from matplotlib import pylab