Require classical_reg in Program.measure() and ilk (#821)

Closes #248

pyquil/gates.py

@@ -474,7 +474,7 @@ def RESET(qubit_index=None):
 """
 
 
-def MEASURE(qubit, classical_reg=None):
+def MEASURE(qubit, classical_reg):
     """
     Produce a MEASURE instruction.
 

pyquil/magic.py

@@ -196,7 +196,7 @@ def magicquil(f):
 
         @magicquil
         def fast_reset(q1):
-            reg1 = MEASURE(q1)
+            reg1 = MEASURE(q1, None)
             if reg1:
                 X(q1)
             else:

pyquil/quil.py

@@ -152,7 +152,7 @@ def inst(self, *instructions):
                     op = instruction[0]
                     if op == "MEASURE":
                         if len(instruction) == 2:
-                            self.measure(instruction[1])
+                            self.measure(instruction[1], None)
                         else:
                             self.measure(instruction[1], instruction[2])
                     else:
@@ -290,12 +290,13 @@ def no_noise(self):
         """
         return self.inst(Pragma("NO-NOISE"))
 
-    def measure(self, qubit_index, classical_reg=None):
+    def measure(self, qubit_index, classical_reg):
         """
         Measures a qubit at qubit_index and puts the result in classical_reg
 
         :param int qubit_index: The address of the qubit to measure.
         :param int classical_reg: The address of the classical bit to store the result.
+            Set to None to measure for effect (discard result).
         :returns: The Quil Program with the appropriate measure instruction appended, e.g.
                   MEASURE 0 [1]
         :rtype: Program

pyquil/quilbase.py

@@ -163,7 +163,7 @@ class Measurement(AbstractInstruction):
     This is the pyQuil object for a Quil measurement instruction.
     """
 
-    def __init__(self, qubit, classical_reg=None):
+    def __init__(self, qubit, classical_reg):
         if not isinstance(qubit, (Qubit, QubitPlaceholder)):
             raise TypeError("qubit should be a Qubit")
         if classical_reg and not isinstance(classical_reg, MemoryReference):

pyquil/tests/test_latex.py

@@ -8,7 +8,7 @@ def test_to_latex():
     """A test to give full coverage of latex_generation and latex_config."""
     qubits = range(3)
     p = Program()
-    p.inst(X(qubits[0]), Y(qubits[0]), CZ(qubits[0], qubits[2]), SWAP(qubits[0], qubits[1]), MEASURE(qubits[0]),
+    p.inst(X(qubits[0]), Y(qubits[0]), CZ(qubits[0], qubits[2]), SWAP(qubits[0], qubits[1]), MEASURE(qubits[0], None),
            CNOT(qubits[2], qubits[0]))
     _ = to_latex(p)
 

pyquil/tests/test_parser.py

@@ -141,7 +141,7 @@ def _expr(expression, expected):
 
 
 def test_measure():
-    parse_equals("MEASURE 0", MEASURE(0))
+    parse_equals("MEASURE 0", MEASURE(0, None))
     parse_equals("MEASURE 0 ro[1]", MEASURE(0, 1))
 
 

pyquil/tests/test_quil.py

@@ -1029,7 +1029,7 @@ def test_validate_supported_quil_reset_qubit():
 
 def test_validate_supported_quil_measure_last():
     prog = Program(
-        MEASURE(0),
+        MEASURE(0, None),
         H(0),
     )
     with pytest.raises(ValueError):
@@ -1042,7 +1042,7 @@ def test_validate_supported_quil_with_pragma():
         RESET(),
         H(1),
         Pragma('DELAY'),
-        MEASURE(1)
+        MEASURE(1, None)
     )
     assert prog.is_supported_on_qpu()
 
@@ -1129,8 +1129,8 @@ def test_validate_supported_quil_multiple_measures():
         RESET(),
         H(1),
         Pragma('DELAY'),
-        MEASURE(1),
-        MEASURE(1)
+        MEASURE(1, None),
+        MEASURE(1, None)
     )
     with pytest.raises(ValueError):
         validate_supported_quil(prog)