# -*- coding: utf-8 -*-
# This code is part of Qiskit.
#
# (C) Copyright IBM 2019, 2020.
#
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
#
# Any modifications or derivative works of this code must retain this
# copyright notice, and modified files need to carry a notice indicating
# that they have been altered from the originals.
"""Variable interface"""
from enum import Enum
from typing import Tuple, Union, Any
from .quadratic_program_element import QuadraticProgramElement
from ..exceptions import QiskitOptimizationError
from ..infinity import INFINITY
class VarType(Enum):
"""Constants defining variable type."""
CONTINUOUS = 0
BINARY = 1
INTEGER = 2
[docs]class Variable(QuadraticProgramElement):
"""Representation of a variable."""
Type = VarType
def __init__(self, quadratic_program: Any, name: str,
lowerbound: Union[float, int] = 0,
upperbound: Union[float, int] = INFINITY,
vartype: VarType = VarType.CONTINUOUS) -> None:
"""Creates a new Variable.
The variables is exposed by the top-level `QuadraticProgram` class
in `QuadraticProgram.variables`. This constructor is not meant to be used
externally.
Args:
quadratic_program: The parent QuadraticProgram.
name: The variable name.
lowerbound: The variable lowerbound.
upperbound: The variable upperbound.
vartype: The variable type.
Raises:
QiskitOptimizationError: if lowerbound is greater than upperbound.
"""
if lowerbound > upperbound:
raise QiskitOptimizationError("Lowerbound is greater than upperbound!")
super().__init__(quadratic_program)
self._name = name
self._lowerbound = lowerbound
self._upperbound = upperbound
self._vartype = vartype
@property
def name(self) -> str:
"""Returns the name of the variable.
Returns:
The name of the variable.
"""
return self._name
@property
def lowerbound(self) -> Union[float, int]:
"""Returns the lowerbound of the variable.
Returns:
The lower bound of the variable.
"""
return self._lowerbound
@lowerbound.setter
def lowerbound(self, lowerbound: Union[float, int]) -> None:
"""Sets the lowerbound of the variable.
Args:
lowerbound: The lower bound of the variable.
Raises:
QiskitOptimizationError: if lowerbound is greater than upperbound.
"""
if lowerbound > self.upperbound:
raise QiskitOptimizationError("Lowerbound is greater than upperbound!")
self._lowerbound = lowerbound
@property
def upperbound(self) -> Union[float, int]:
"""Returns the upperbound of the variable.
Returns:
The upperbound of the variable.
"""
return self._upperbound
@upperbound.setter
def upperbound(self, upperbound: Union[float, int]) -> None:
"""Sets the upperbound of the variable.
Args:
upperbound: The upperbound of the variable.
Raises:
QiskitOptimizationError: if upperbound is smaller than lowerbound.
"""
if self.lowerbound > upperbound:
raise QiskitOptimizationError("Lowerbound is greater than upperbound!")
self._upperbound = upperbound
@property
def vartype(self) -> VarType:
"""Returns the type of the variable.
Returns:
The variable type.
"""
return self._vartype
@vartype.setter
def vartype(self, vartype: VarType) -> None:
"""Sets the type of the variable.
Args:
vartype: The variable type.
"""
self._vartype = vartype
[docs] def as_tuple(self) -> Tuple[str, Union[float, int], Union[float, int], VarType]:
""" Returns a tuple corresponding to this variable.
Returns:
A tuple corresponding to this variable consisting of name, lowerbound, upperbound and
variable type.
"""
return self.name, self.lowerbound, self.upperbound, self.vartype