# -*- coding: utf-8 -*-
# This code is part of Qiskit.
#
# (C) Copyright IBM 2017.
#
# 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.
"""
Classical register reference object.
"""
import itertools
from qiskit.circuit.exceptions import CircuitError
from .register import Register
from .bit import Bit
[docs]class Clbit(Bit):
"""Implement a classical bit."""
def __init__(self, register, index):
"""Creates a classical bit.
Args:
register (ClassicalRegister): a classical register.
index (int): the index to insert the bit
Raises:
CircuitError: if the provided register is not a valid :class:`ClassicalRegister`
"""
if isinstance(register, ClassicalRegister):
super().__init__(register, index)
else:
raise CircuitError('Clbit needs a ClassicalRegister and %s was provided' %
type(register).__name__)
[docs]class ClassicalRegister(Register):
"""Implement a classical register."""
# Counter for the number of instances in this class.
instances_counter = itertools.count()
# Prefix to use for auto naming.
prefix = 'c'
bit_type = Clbit
[docs] def qasm(self):
"""Return OPENQASM string for this register."""
return "creg %s[%d];" % (self.name, self.size)