Added get_qasm support for ControlledGates

bqskit/ir/gates/composed/controlled.py

@@ -9,6 +9,7 @@
 
 from bqskit.ir.gate import Gate
 from bqskit.ir.gates.composedgate import ComposedGate
+from bqskit.ir.location import CircuitLocation
 from bqskit.qis.unitary.differentiable import DifferentiableUnitary
 from bqskit.qis.unitary.unitary import RealVector
 from bqskit.qis.unitary.unitarymatrix import UnitaryMatrix
@@ -286,6 +287,23 @@ def __init__(
             ctrl_U = np.kron(self.ctrl, U) + self.ihalf
             self._utry = UnitaryMatrix(ctrl_U, self.radixes)
 
+    def get_qasm(self, params: RealVector, location: CircuitLocation) -> str:
+        """
+        Override default `Gate.get_qasm` method.
+
+        If the target gate is a standard gate, this function will output
+        qasm in the form 'c+<gate_qasm>'. Otherwise an error will be raised.
+
+        Raises:
+            AttributeError: If the target gate is non-standard.
+        """
+        qasm_name = 'c' * self.num_controls + self.gate.qasm_name
+        return '{}({}) q[{}];\n'.format(
+            qasm_name,
+            ', '.join([str(p) for p in params]),
+            '], q['.join([str(q) for q in location]),
+        ).replace('()', '')
+
     def get_unitary(self, params: RealVector = []) -> UnitaryMatrix:
         """Return the unitary for this gate, see :class:`Unitary` for more."""
         if hasattr(self, '_utry'):

tests/ir/lang/test_controlled_qasm.py

@@ -0,0 +1,33 @@
+from __future__ import annotations
+
+from bqskit.ir.lang.qasm2 import OPENQASM2Language
+
+
+class TestControlledQASM:
+    def test_cu1(self) -> None:
+
+        input_qasm = (
+            'OPENQASM 2.0;\n'
+            'include "qelib1.inc";\n'
+            'qreg q[2];\n'
+            'cu1(3.1415) q[0], q[1];\n'
+        )
+        circuit = OPENQASM2Language().decode(input_qasm)
+
+        output_qasm = circuit.to('qasm')
+
+        assert input_qasm == output_qasm
+
+    def test_cu3(self) -> None:
+
+        input_qasm = (
+            'OPENQASM 2.0;\n'
+            'include "qelib1.inc";\n'
+            'qreg q[2];\n'
+            'cu3(3.1415, 0.0, -4.0) q[0], q[1];\n'
+        )
+        circuit = OPENQASM2Language().decode(input_qasm)
+
+        output_qasm = circuit.to('qasm')
+
+        assert input_qasm == output_qasm