adder error when using parameterized_bitstring_prep

[joshcombes]

see the notebook. get_n_bit_adder_results fails when using parameterized bit string prep need to fix

if use_param_program=True there is an error.

n_bits = 2
# set in_x_basis to true here
results = get_n_bit_adder_results(noisy_qc, n_bits, use_param_program=True, in_x_basis=True)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-16-3b31c8ccf0a4> in <module>
      1 n_bits = 2
      2 # set in_x_basis to true here
----> 3 results = get_n_bit_adder_results(noisy_qc, n_bits, use_param_program=True, in_x_basis=True)
      4 distributions = get_error_hamming_distributions_from_results(results)
      5 

~/forest-benchmarking/forest/benchmarking/classical_logic/ripple_carry_adder.py in get_n_bit_adder_results(qc, n_bits, registers, qubits, in_x_basis, num_shots, use_param_program, use_active_reset)
    304         # Run it on the QPU or QVM
    305         if use_param_program:
--> 306             results = qc.run(exe, memory_map={REG_NAME: bits})
    307         else:
    308             results = qc.run(exe)

~/pyquil/pyquil/api/_error_reporting.py in wrapper(*args, **kwargs)
    236             global_error_context.log[key] = pre_entry
    237 
--> 238         val = func(*args, **kwargs)
    239 
    240         # poke the return value of that call in

~/pyquil/pyquil/api/_quantum_computer.py in run(self, executable, memory_map)
    126                     # TODO gh-658: have write_memory take a list rather than value + offset
    127                     self.qam.write_memory(region_name=region_name, offset=offset, value=value)
--> 128         return self.qam.run() \
    129             .wait() \
    130             .read_memory(region_name='ro')

~/pyquil/pyquil/api/_error_reporting.py in wrapper(*args, **kwargs)
    236             global_error_context.log[key] = pre_entry
    237 
--> 238         val = func(*args, **kwargs)
    239 
    240         # poke the return value of that call in

~/pyquil/pyquil/api/_qvm.py in run(self)
    510             quil_program = apply_noise_model(quil_program, self.noise_model)
    511 
--> 512         quil_program = self.augment_program_with_memory_values(quil_program)
    513         try:
    514             self._bitstrings = self.connection._qvm_run(quil_program=quil_program,

~/pyquil/pyquil/api/_qvm.py in augment_program_with_memory_values(self, quil_program)
    530 
    531         for k, v in self._variables_shim.items():
--> 532             p += MOVE(MemoryReference(name=k.name, offset=k.index), v)
    533 
    534         p += quil_program

~/pyquil/pyquil/gates.py in MOVE(classical_reg1, classical_reg2)
    602     :return: A ClassicalMove instance.
    603     """
--> 604     left, right = unpack_reg_val_pair(classical_reg1, classical_reg2)
    605     return ClassicalMove(left, right)
    606 

~/pyquil/pyquil/gates.py in unpack_reg_val_pair(classical_reg1, classical_reg2)
     39         right = classical_reg2
     40     else:
---> 41         right = unpack_classical_reg(classical_reg2)
     42 
     43     return left, right

~/pyquil/pyquil/quilatom.py in unpack_classical_reg(c)
    144         return MemoryReference(c, 0)
    145     else:
--> 146         raise TypeError("c should be a list of length 2, a pair, a string, or a MemoryReference")
    147 
    148 

TypeError: c should be a list of length 2, a pair, a string, or a MemoryReference