relationalai.experimental.solvers.implies()
implies(left: SolverExpression, right: SolverExpression) -> SolverExpression
Returns a solver expression representing a logical implication: if left
is true, then right
must also be true.
Both left
and right
must be binary-valued solver expressions, such as binary variables or logical comparisons.
Must be called in a Model.rule()
or solvers.operators()
context.
Parameters
Section titled “Parameters”Name | Type | Description |
---|---|---|
left | SolverExpression | The condition that riggers the implication. Must evaluate to a binary value (True /False or 1 /0 ), such as a binary variable or a logical comparison. |
right | SolverExpression | The outcome enforced when left is true. Must also evaluate to a binary value. |
Returns
Section titled “Returns”A SolverExpression
object.
Example
Section titled “Example”Use implies()
with the SolverModel.constraint()
method to encode a dependency between two conditions:
import relationalai as raifrom relationalai.experimental import solvers
# Create a RAI model.model = rai.Model("WeeklyShiftAssignment")
# Declare entity types and properties.
# Entity types.Employee = model.Type("Employee")Shift = model.Type("Shift")Day = model.Type("Day")Available = model.Type("Available")Scenario = model.Type("Scenario") # All possible employee–shift–day combinations.Assignment = model.Type("Assignment") # A Scenario that is assigned.
# Properties.Employee.name.declare()Shift.name.declare()Shift.capacity.declare()Available.employee.declare()Available.day.declare()Scenario.employee.declare()Scenario.shift.declare()Scenario.day.declare()
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# Define sample data.
# Employees.with model.rule(dynamic=True): for name in ["Alice", "Bob", "Carol", "Dave", "Eve"]: Employee.add(name=name)
# Shifts.with model.rule(): Shift.add(name="Morning").set(capacity=2) Shift.add(name="Evening").set(capacity=3)
# Days of the week.with model.rule(dynamic=True): for name in ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]: Day.add(name=name)
# Employee-day availability.with model.rule(dynamic=True): # Alice works weekdays only for name in ["Mon", "Tue", "Wed", "Thu", "Fri"]: Available.add(employee=Employee(name="Alice"), day=Day(name=name)) # Bob works all days Available.add(employee=Employee(name="Bob"), day=Day()) # Carol works weekends only for name in ["Sat", "Sun"]: Available.add(employee=Employee(name="Carol"), day=Day(name=name)) # Dave works Mon/Wed/Fri for name in ["Mon", "Wed", "Fri"]: Available.add(employee=Employee(name="Dave"), day=Day(name=name)) # Eve works Tue/Thu/Sat for name in ["Tue", "Thu", "Sat"]: Available.add(employee=Employee(name="Eve"), day=Day(name=name))
# All possible employee–shift–day combinationswith model.rule(): Scenario.add(employee=Employee(), shift=Shift(), day=Day())
# Create a SolverModel instance from the model.solver_model = solvers.SolverModel(model)
# Define solver variables.
# Scenario assignment: binary variable for each employee–shift–day combination.with model.rule(): scenario = Scenario() solver_model.variable( scenario, type="zero_one", name_args=["assigned", scenario.employee.name, scenario.day.name, scenario.shift.name], )
# Define solver constraints.
# If an employee is assigned the morning shift, they are not assigned the evening shift on the same day.with solvers.operators(): works_morning = Scenario(shift=Shift(name="Morning")) works_evening = Scenario( shift=Shift(name="Evening"), employee=works_morning.employee, day=works_morning.day ) solver_model.constraint( solvers.implies(works_morning, solvers.not_(works_evening)) )