# Source code for ufl.equation

"""The Equation class, used to express equations like a == L."""
# Copyright (C) 2012-2016 Anders Logg and Martin Sandve Alnæs
#
# This file is part of UFL (https://www.fenicsproject.org)
#
# SPDX-License-Identifier: LGPL-3.0-or-later
# Export list for ufl.classes
__all_classes__ = ["Equation"]
[docs]class Equation(object):
"""Equation.
This class is used to represent equations expressed by the "=="
operator. Examples include a == L and F == 0 where a, L and F are
Form objects.
"""
def __init__(self, lhs, rhs):
"""Create equation lhs == rhs."""
self.lhs = lhs
self.rhs = rhs
def __bool__(self):
"""Evaluate bool(lhs_form == rhs_form).
This will not trigger when setting 'equation = a == L',
but when e.g. running 'if equation:'.
"""
# NB!: pep8 will say you should use isinstance here, but we do
# actually want to compare the exact types in this case.
# Not equal if types are not identical (i.e. not accepting
# subclasses)
if type(self.lhs) != type(self.rhs): # noqa: E721
return False
# Try to delegate to equals function
if hasattr(self.lhs, "equals"):
return self.lhs.equals(self.rhs)
elif hasattr(self.rhs, "equals"):
return self.rhs.equals(self.lhs)
else:
raise ValueError("Either lhs or rhs of Equation must implement self.equals(other).")
__nonzero__ = __bool__
def __eq__(self, other):
"""Compare two equations by comparing lhs and rhs."""
return isinstance(other, Equation) and self.lhs == other.lhs and self.rhs == other.rhs
def __hash__(self):
"""Hash."""
return hash((hash(self.lhs), hash(self.rhs)))
def __repr__(self):
"""Representation."""
return f"Equation({self.lhs!r}, {self.rhs!r})"