Deprecate qiskit.circuit.classicalfunction

qiskit/circuit/classicalfunction/__init__.py

@@ -20,6 +20,10 @@
 Overview
 ========
 
+.. warning::
+
+    This module is deprecated as of Qiskit 1.4.0. It will be removed in the Qiskit 2.0 release.
+
 The classical function compiler provides the necessary tools to map a classical
 potentially irreversible functions into quantum circuits.  Below is a simple example of
 how to synthesize a simple boolean function defined using Python into a
@@ -111,7 +115,7 @@ def grover_oracle(a: Int1, b: Int1, c: Int1, d: Int1) -> Int1:
    ClassicalFunctionCompilerTypeError
 
 """
-
+from qiskit.utils.deprecation import deprecate_func
 from .classicalfunction import ClassicalFunction
 from .exceptions import (
     ClassicalFunctionParseError,
@@ -121,6 +125,13 @@ def grover_oracle(a: Int1, b: Int1, c: Int1, d: Int1) -> Int1:
 from .boolean_expression import BooleanExpression
 
 
+@deprecate_func(
+    since="1.4",
+    removal_timeline="in Qiskit 2.0",
+    additional_msg="Use `PhaseOracle` instead, which can be turned into a "
+    "bit-flip oracle by applying Hadamard gates on the target "
+    "qubit before and after the instruction.",
+)
 def classical_function(func):
     """
     Parses and type checks the callable ``func`` to compile it into an ``ClassicalFunction``

qiskit/circuit/classicalfunction/boolean_expression.py

@@ -15,15 +15,23 @@
 from os.path import basename, isfile
 from typing import Callable, Optional
 
+from qiskit.utils.deprecation import deprecate_func
 from qiskit.circuit import QuantumCircuit
 from qiskit.utils.optionals import HAS_TWEEDLEDUM
 from .classical_element import ClassicalElement
 
 
-@HAS_TWEEDLEDUM.require_in_instance
 class BooleanExpression(ClassicalElement):
     """The Boolean Expression gate."""
 
+    @HAS_TWEEDLEDUM.require_in_instance
+    @deprecate_func(
+        since="1.4",
+        removal_timeline="in Qiskit 2.0",
+        additional_msg="Use `PhaseOracle` instead, which can be turned into a "
+        "bit-flip oracle by applying Hadamard gates on the target "
+        "qubit before and after the instruction.",
+    )
     def __init__(self, expression: str, name: str = None, var_order: list = None) -> None:
         """
         Args:

qiskit/circuit/classicalfunction/classicalfunction.py

@@ -15,6 +15,7 @@
 import ast
 from typing import Callable, Optional
 
+from qiskit.utils.deprecation import deprecate_func
 from qiskit.circuit import QuantumCircuit, QuantumRegister
 from qiskit.exceptions import QiskitError
 from qiskit.utils.optionals import HAS_TWEEDLEDUM
@@ -23,10 +24,17 @@
 from .utils import tweedledum2qiskit
 
 
-@HAS_TWEEDLEDUM.require_in_instance
 class ClassicalFunction(ClassicalElement):
     """Represent a classical function and its logic network."""
 
+    @HAS_TWEEDLEDUM.require_in_instance
+    @deprecate_func(
+        since="1.4",
+        removal_timeline="in Qiskit 2.0",
+        additional_msg="Use `PhaseOracle` instead, which can be turned into a "
+        "bit-flip oracle by applying Hadamard gates on the target "
+        "qubit before and after the instruction.",
+    )
     def __init__(self, source, name=None):
         """Creates a ``ClassicalFunction`` from Python source code in ``source``.
 

qiskit/circuit/classicalfunction/exceptions.py

@@ -10,7 +10,13 @@
 # copyright notice, and modified files need to carry a notice indicating
 # that they have been altered from the originals.
 
-"""Exceptions for ClassicalFunction compiler"""
+"""Exceptions for ClassicalFunction compiler
+
+.. warning::
+
+    This module is deprecated as of qiskit 1.4.0 version. It will be removed in the Qiskit 2.0 release.
+
+"""
 
 from qiskit.exceptions import QiskitError
 

qiskit/circuit/library/phase_oracle.py

@@ -63,6 +63,11 @@ def __init__(
             var_order(list): A list with the order in which variables will be created.
                (default: by appearance)
         """
+        # ignore deprecation warning for BooleanExpression; implementation is changing in 2.0
+        import warnings
+
+        warnings.simplefilter("ignore", DeprecationWarning)
+
         from qiskit.circuit.classicalfunction.boolean_expression import BooleanExpression
         from qiskit.circuit.classicalfunction.classical_element import ClassicalElement
 

releasenotes/notes/deprecate-classical-function-3bf44ef26d984366.yaml

@@ -0,0 +1,12 @@
+---
+deprecations_circuits:
+  - |
+    The :mod:`qiskit.circuit.classicalfunction` and with it
+    the :class:`.ClassicalFunction`, its related :func:`.classical_function`
+    and :class:`.BooleanExpression` have been deprecated as of Qiskit 1.4 
+    and will be removed in Qiskit 2.0. This change is done to avoid a 
+    dependency on the external library `tweedledum`, which is no longer 
+    compatible with all of Qiskit's supported platforms and Python versions.
+    For a similar functionality please use the :class:`.PhaseOracle` which
+    is going to have a `tweedledum` independent implementation, and
+    the :class:`.BitFlipOracle` which will be added in Qiskit 2.0.

test/python/classical_function_compiler/test_boolean_expression.py

@@ -40,7 +40,11 @@ class TestBooleanExpression(QiskitTestCase):
     @unpack
     def test_evaluate(self, expression, input_bitstring, expected):
         """Test simulate"""
-        expression = BooleanExpression(expression)
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            expected_regex="BooleanExpression`` is deprecated as of qiskit 1.4",
+        ):
+            expression = BooleanExpression(expression)
         result = expression.simulate(input_bitstring)
         self.assertEqual(result, expected)
 
@@ -53,7 +57,11 @@ def test_evaluate(self, expression, input_bitstring, expected):
     @unpack
     def test_synth(self, expression, expected):
         """Test synth"""
-        expression = BooleanExpression(expression)
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            expected_regex="BooleanExpression`` is deprecated as of qiskit 1.4",
+        ):
+            expression = BooleanExpression(expression)
         expr_circ = expression.synth()
 
         new_creg = expr_circ._create_creg(1, "c")

test/python/classical_function_compiler/test_classical_function.py

@@ -31,7 +31,11 @@ class TestOracleDecomposition(QiskitTestCase):
 
     def test_grover_oracle(self):
         """grover_oracle.decomposition"""
-        oracle = compile_classical_function(examples.grover_oracle)
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            expected_regex="ClassicalFunction`` is deprecated as of qiskit 1.4",
+        ):
+            oracle = compile_classical_function(examples.grover_oracle)
         quantum_circuit = QuantumCircuit(5)
         quantum_circuit.append(oracle, [2, 1, 0, 3, 4])
 

test/python/classical_function_compiler/test_parse.py

@@ -35,23 +35,39 @@ def assertExceptionMessage(self, context, message):
     def test_id_bad_return(self):
         """Trying to parse examples.id_bad_return raises ClassicalFunctionParseError"""
         with self.assertRaises(ClassicalFunctionParseError) as context:
-            compile_classical_function(examples.id_bad_return)
+            with self.assertWarnsRegex(
+                DeprecationWarning,
+                expected_regex="ClassicalFunction`` is deprecated as of Qiskit 1.4",
+            ):
+                compile_classical_function(examples.id_bad_return)
         self.assertExceptionMessage(context, "return type error")
 
     def test_id_no_type_arg(self):
         """Trying to parse examples.id_no_type_arg raises ClassicalFunctionParseError"""
         with self.assertRaises(ClassicalFunctionParseError) as context:
-            compile_classical_function(examples.id_no_type_arg)
+            with self.assertWarnsRegex(
+                DeprecationWarning,
+                expected_regex="ClassicalFunction`` is deprecated as of Qiskit 1.4",
+            ):
+                compile_classical_function(examples.id_no_type_arg)
         self.assertExceptionMessage(context, "argument type is needed")
 
     def test_id_no_type_return(self):
         """Trying to parse examples.id_no_type_return raises ClassicalFunctionParseError"""
         with self.assertRaises(ClassicalFunctionParseError) as context:
-            compile_classical_function(examples.id_no_type_return)
+            with self.assertWarnsRegex(
+                DeprecationWarning,
+                expected_regex="ClassicalFunction`` is deprecated as of Qiskit 1.4",
+            ):
+                compile_classical_function(examples.id_no_type_return)
         self.assertExceptionMessage(context, "return type is needed")
 
     def test_out_of_scope(self):
         """Trying to parse examples.out_of_scope raises ClassicalFunctionParseError"""
         with self.assertRaises(ClassicalFunctionParseError) as context:
-            compile_classical_function(examples.out_of_scope)
+            with self.assertWarnsRegex(
+                DeprecationWarning,
+                expected_regex="ClassicalFunction`` is deprecated as of Qiskit 1.4",
+            ):
+                compile_classical_function(examples.out_of_scope)
         self.assertExceptionMessage(context, "out of scope: c")

test/python/classical_function_compiler/test_simulate.py

@@ -32,6 +32,10 @@ class TestSimulate(QiskitTestCase):
     @data(*utils.example_list())
     def test_(self, a_callable):
         """Tests LogicSimulate.simulate() on all the examples"""
-        network = compile_classical_function(a_callable)
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            expected_regex="ClassicalFunction`` is deprecated as of qiskit 1.4",
+        ):
+            network = compile_classical_function(a_callable)
         truth_table = network.simulate_all()
         self.assertEqual(truth_table, utils.get_truthtable_from_function(a_callable))

test/python/classical_function_compiler/test_synthesis.py

@@ -31,7 +31,11 @@ class TestSynthesis(QiskitTestCase):
 
     def test_grover_oracle(self):
         """Synthesis of grover_oracle example"""
-        oracle = compile_classical_function(examples.grover_oracle)
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            expected_regex="ClassicalFunction`` is deprecated as of qiskit 1.4",
+        ):
+            oracle = compile_classical_function(examples.grover_oracle)
         quantum_circuit = oracle.synth()
 
         expected = QuantumCircuit(5)
@@ -42,7 +46,11 @@ def test_grover_oracle(self):
 
     def test_grover_oracle_arg_regs(self):
         """Synthesis of grover_oracle example with arg_regs"""
-        oracle = compile_classical_function(examples.grover_oracle)
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            expected_regex="ClassicalFunction`` is deprecated as of qiskit 1.4",
+        ):
+            oracle = compile_classical_function(examples.grover_oracle)
         quantum_circuit = oracle.synth(registerless=False)
 
         qr_a = QuantumRegister(1, "a")

test/python/classical_function_compiler/test_typecheck.py

@@ -30,43 +30,67 @@ class TestTypeCheck(QiskitTestCase):
 
     def test_id(self):
         """Tests examples.identity type checking"""
-        network = compile_classical_function(examples.identity)
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            expected_regex="ClassicalFunction`` is deprecated as of qiskit 1.4",
+        ):
+            network = compile_classical_function(examples.identity)
         self.assertEqual(network.args, ["a"])
         self.assertEqual(network.types, [{"Int1": "type", "a": "Int1", "return": "Int1"}])
 
     def test_bool_not(self):
         """Tests examples.bool_not type checking"""
-        network = compile_classical_function(examples.bool_not)
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            expected_regex="ClassicalFunction`` is deprecated as of qiskit 1.4",
+        ):
+            network = compile_classical_function(examples.bool_not)
         self.assertEqual(network.args, ["a"])
         self.assertEqual(network.types, [{"Int1": "type", "a": "Int1", "return": "Int1"}])
 
     def test_id_assign(self):
         """Tests examples.id_assing type checking"""
-        network = compile_classical_function(examples.id_assing)
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            expected_regex="ClassicalFunction`` is deprecated as of qiskit 1.4",
+        ):
+            network = compile_classical_function(examples.id_assing)
         self.assertEqual(network.args, ["a"])
         self.assertEqual(
             network.types, [{"Int1": "type", "a": "Int1", "b": "Int1", "return": "Int1"}]
         )
 
     def test_bit_and(self):
         """Tests examples.bit_and type checking"""
-        network = compile_classical_function(examples.bit_and)
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            expected_regex="ClassicalFunction`` is deprecated as of qiskit 1.4",
+        ):
+            network = compile_classical_function(examples.bit_and)
         self.assertEqual(network.args, ["a", "b"])
         self.assertEqual(
             network.types, [{"Int1": "type", "a": "Int1", "b": "Int1", "return": "Int1"}]
         )
 
     def test_bit_or(self):
         """Tests examples.bit_or type checking"""
-        network = compile_classical_function(examples.bit_or)
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            expected_regex="ClassicalFunction`` is deprecated as of qiskit 1.4",
+        ):
+            network = compile_classical_function(examples.bit_or)
         self.assertEqual(network.args, ["a", "b"])
         self.assertEqual(
             network.types, [{"Int1": "type", "a": "Int1", "b": "Int1", "return": "Int1"}]
         )
 
     def test_bool_or(self):
         """Tests examples.bool_or type checking"""
-        network = compile_classical_function(examples.bool_or)
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            expected_regex="ClassicalFunction`` is deprecated as of qiskit 1.4",
+        ):
+            network = compile_classical_function(examples.bool_or)
         self.assertEqual(network.args, ["a", "b"])
         self.assertEqual(
             network.types, [{"Int1": "type", "a": "Int1", "b": "Int1", "return": "Int1"}]
@@ -88,5 +112,9 @@ def test_bit_not(self):
         ~False  # -1
         """
         with self.assertRaises(ClassicalFunctionCompilerTypeError) as context:
-            compile_classical_function(bad_examples.bit_not)
+            with self.assertWarnsRegex(
+                DeprecationWarning,
+                expected_regex="ClassicalFunction`` is deprecated as of qiskit 1.4",
+            ):
+                compile_classical_function(bad_examples.bit_not)
         self.assertExceptionMessage(context, "does not operate with Int1 type")

test/python/visualization/test_circuit_text_drawer.py

@@ -1397,12 +1397,16 @@ def test_text_synth_no_registerless(self):
                 "           └───┘",
             ]
         )
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            expected_regex=r"classical_function\(\)`` is deprecated as of qiskit 1.4",
+        ):
 
-        @classical_function
-        def grover_oracle(a: Int1, b: Int1, c: Int1) -> Int1:
-            return a and b and not c
+            @classical_function
+            def grover_oracle(a: Int1, b: Int1, c: Int1) -> Int1:
+                return a and b and not c
 
-        circuit = grover_oracle.synth(registerless=False)
+            circuit = grover_oracle.synth(registerless=False)
         self.assertEqual(str(circuit_drawer(circuit, output="text", initial_state=True)), expected)