def test_evaluate_where_possible_simple(self):
two_plus_two = Operation(OperationType.PLUS(),
[Variable(2.0), Variable(2.0)])
expression = Operation(OperationType.DIVIDE(),
[Variable('x'), two_plus_two])
verify(str(expression.evaluate_where_possible()), self.reporter)
def test_complex_operation(self):
two = Operation(OperationType.POSITIVE(), [Variable(2)])
negative_x = Operation(OperationType.NEGATIVE(), [Variable('x')])
op = Operation(OperationType.TIMES(), [two, negative_x])
verify(str(op), self.reporter)
def parse(self, parser):
assert isinstance(parser, Parser)
if self._operation_type in self.token_map.values():
right = parser.parse(precedence=10) # All prefixes should be evaluated before infixes
return Operation(self._operation_type, [right])
else:
return Operation(self._operation_type)
def test_evaluation_simple(self):
two_plus_two = Operation(OperationType.PLUS(),
[Variable(2.0), Variable(2.0)])
two_plus_two_divided_by_four = Operation(
OperationType.DIVIDE(), [two_plus_two, Variable(4)])
self.assertTrue(two_plus_two_divided_by_four.is_evaluatable())
self.assertAlmostEqual(two_plus_two_divided_by_four.evaluate(), 1)
def test_collected_terms_subtract(self):
x = Term(Operation(Variable('x')))
y = Term(Operation(Variable('y')), 2)
z = Term(Operation(Variable('z')))
expression1 = CollectedTerms([x, y], [1, 3])
expression2 = CollectedTerms([y, z], [-3, -2])
result = CollectedTerms.subtract(expression1, expression2)
verify(str(result), self.reporter)
def test_equation(self):
two = Operation(OperationType.POSITIVE(), [Variable(2)])
negative_x = Operation(OperationType.NEGATIVE(), [Variable('x')])
lhs = Operation(OperationType.TIMES(), [two, negative_x])
rhs = Variable(3.1415)
eq = Equation(lhs, rhs)
verify(str(eq), self.reporter)
def apply_function(equation):
if equation.lhs.operation_type.arity == 0:
equation = equation.flip()
if (equation.rhs.operation_type.arity
== 0) and (equation.rhs.operation_type.symbol == '0'):
homogenized = equation.lhs
else:
homogenized = Operation(OperationType.MINUS(),
[equation.lhs, equation.rhs])
collected = CollectedTerms.try_parse_expression(homogenized)
if collected is None:
return equation
collected = collected.as_expression
return Equation(collected, Operation(Variable(0)))
def parse(self, parser, left):
assert isinstance(parser, Parser)
assert isinstance(left, Operation)
right = parser.parse(self.precedence)
return Operation(self._operation_type, [left, right])
def apply(self, equation):
assert isinstance(equation, Equation)
assert self.is_applicable_to(equation)
assert len(equation.lhs.arguments) == 2
operand = equation.lhs.arguments[1]
lhs = equation.lhs.arguments[0]
rhs = Operation(self._inverse_type, [equation.rhs, operand])
return Equation(lhs, rhs)
def test_collected_terms_instantiate(self):
x = Term(Operation(Variable('x')))
expression1 = CollectedTerms([x], [1])
self.assertEqual(str(expression1), 'x')
expression2 = CollectedTerms([x], [5])
self.assertEqual(str(expression2), '5.0x')
expression3 = CollectedTerms([x], [-1])
self.assertEqual(str(expression3), '-x')
expression4 = CollectedTerms([x], [-12])
self.assertEqual(str(expression4), '-12.0x')
def test_evaluation_trivial(self):
two = Operation(OperationType.POSITIVE(), [Variable('2')])
self.assertTrue(two.is_evaluatable())
self.assertAlmostEqual(two.evaluate(), 2)
x = Operation(OperationType.POSITIVE(), [Variable('x')])
self.assertFalse(x.is_evaluatable())
def _substitute(self, operation, pattern):
if operation.operation_type.arity == 0:
if operation.operation_type.symbol in pattern.keys():
return pattern[operation.operation_type.symbol]
else:
return operation
to_return_op_type = operation.operation_type
to_return_arguments = list()
for sub_op in operation.arguments:
to_return_arguments.append(self._substitute(sub_op, pattern))
return Operation(to_return_op_type, to_return_arguments)
def transform(self, expression, pattern=None):
assert isinstance(expression, Operation)
if pattern is None:
assert isinstance(pattern, SubstitutionPattern)
for k in pattern.keys():
if type(pattern[k]) == str:
pattern[k] = Operation(OperationType.VARIABLE(pattern[k]))
substituted_start = self.try_transform(expression, pattern)
substituted_end = self._substitute(self._end, pattern)
return substituted_end
def test_evaluate_where_possible_complex(self):
two_plus_two = Operation(OperationType.PLUS(),
[Variable(2.0), Variable(2.0)])
two_plus_two_divided_by_four = Operation(
OperationType.DIVIDE(), [two_plus_two, Variable(4)])
three_minus_x = Operation(OperationType.MINUS(),
[Variable(3.0), Variable('x')])
seven_plus_five = Operation(OperationType.PLUS(),
[Variable(7), Variable(5)])
three_minus_x_over_seven_plus_five = Operation(
OperationType.DIVIDE(), [three_minus_x, seven_plus_five])
expression = Operation(
OperationType.TIMES(),
[two_plus_two_divided_by_four, three_minus_x_over_seven_plus_five])
verify(str(expression.evaluate_where_possible()), self.reporter)
def try_transform(self, expression, pattern=None):
assert isinstance(expression, Operation)
if pattern is None:
pattern = SubstitutionPattern(dict())
assert isinstance(pattern, SubstitutionPattern)
substituted_start = self._substitute(self._start, pattern)
if not Operation.areEqual(substituted_start, expression):
raise TransformException(
'{} substituted with {} == {} != {}'.format(
str(self._start), str(pattern), str(substituted_start),
str(expression)))
else:
return substituted_start
def flip_transformation(variable_to_force_left):
if type(variable_to_force_left) == str:
variable_to_force_left = Variable(variable_to_force_left)
assert isinstance(variable_to_force_left, Variable)
is_applicable_function = lambda x: True
subexpression = Operation(variable_to_force_left)
def apply_function(equation):
if not (equation.rhs.contains(subexpression)
): # If it appears on both sides, default to flipping
return equation
else:
return equation.flip()
return Transformation(is_applicable_function, apply_function)
def substitutes(self, expression, pattern):
assert isinstance(expression, Operation)
assert isinstance(pattern, SubstitutionPattern)
substituted_start = self._substitute(self._start, pattern)
return Operation.areEqual(substituted_start, expression)
def single_variable(equation,
variable,
print_out=False,
max_iterations=1000):
assert isinstance(equation, Equation)
if type(variable) == str:
variable = Variable(variable)
assert isinstance(variable, Variable)
assert type(print_out) == bool
assert type(max_iterations) == int
assert variable.symbol in equation.get_variables()
expected_result = Operation(variable)
condition = lambda x: (
(Operation.areEqual(x.lhs, expected_result) and variable.symbol not in x.rhs.get_variables())\
or x is None
)
distributions = [
ExpressionSubstitution(Parser.parse_expression('a * (b + c)'),
Parser.parse_expression('a * b + a * c')),
ExpressionSubstitution(Parser.parse_expression('(a + b) * c'),
Parser.parse_expression('a * c + b * c')),
ExpressionSubstitution(Parser.parse_expression('(a + b) / c'),
Parser.parse_expression('a / c + b / c')),
ExpressionSubstitution(Parser.parse_expression('a * (b - c)'),
Parser.parse_expression('a * b - a * c')),
ExpressionSubstitution(Parser.parse_expression('(a - b) * c'),
Parser.parse_expression('a * c - b * c')),
ExpressionSubstitution(Parser.parse_expression('(a - b) / c'),
Parser.parse_expression('a / c - b / c')),
]
distributions = [
Transformation.apply_all_substitution_transformations(x)
for x in distributions
]
distribute = SolverStep(
Transformation.each_transformation(distributions, False))
pre_solve = SolverStep(
Transformation.collect_like_terms_transformation())
equation = distribute.execute_step(equation)
equation = pre_solve.execute_step(equation)
branches = [equation]
executed_branches = set()
iterations = 0
no_regrets_transformations = [
Transformation.apply_all_substitution_transformations(x)\
for x in Solver.no_regrets_substitutions
]
solve_step = SolverStep(Transformation.evaluation_transformation(),
terminate_on_repeat=True)
solve_step_2 = SolverStep(
Transformation.each_transformation(no_regrets_transformations,
False))
solve_step_3 = SolverStep(Transformation.flip_transformation(variable))
solve_step_4 = SolverStep.cancellations()
solve_step.next_step = solve_step_2
solve_step_2.next_step = solve_step_3
solve_step_3.next_step = solve_step_4
solve_step_4.next_step = solve_step
while iterations < max_iterations:
if len(branches) == 0:
raise SolverException('Exhausted possible transformations.')
branch = branches[0]
branches = branches[1:]
if print_out:
print('Executing branch: {}'.format(str(branch)))
result = solve_step.execute_until(branch,
condition,
print_out=print_out)
if condition(result):
final_execute_step = SolverStep(
Transformation.evaluation_transformation())
return final_execute_step.execute_step(result)
else:
executed_branches.add(str(branch))
executed_branches.add(
str(result)) # Executed already since steps terminated
new_branches = dict()
# We don't care about the outputs of flips or cancellations
new_branch_strings = solve_step_3.previous_inputs - executed_branches
for string in new_branch_strings:
new_branches[string] = Parser.parse_equation(string)
solve_step.clear_history()
solve_step_2.clear_history()
solve_step_3.clear_history()
solve_step_4.clear_history()
for substitution in Solver.substitutions:
left_substitution_result = [
x[1]
for x in substitution.get_all_substitutions(branch.lhs)
]
right_substitution_result = [
x[1]
for x in substitution.get_all_substitutions(branch.rhs)
]
equations = [
Equation(x, branch.rhs)
for x in left_substitution_result
]
equations += [
Equation(branch.lhs, x)
for x in right_substitution_result
]
pairs = [(str(x), x) for x in equations
if str(x) not in executed_branches]
for k, v in pairs:
new_branches[k] = v
if print_out:
print("New branches from {}:\n{}\n".format(
str(branch), '\n'.join(new_branches.keys())))
branches += new_branches.values()
branches.sort(key=lambda x: len(str(x)))
iterations += 1
raise SolverException(
'Could not solve equation for a single variable. Final result: {}'
.format(str(equation)))
def test_single_variable_solver_trivial(self):
equation = Equation(Operation(Variable('x')), Operation(Variable(2)))
result = Solver.single_variable(equation, 'x')
verify(str(result), self.reporter)
def test_simple_operation(self):
simple_op = Operation(OperationType.PLUS(), [Variable(2), Variable(2)])
verify(str(simple_op), self.reporter)
