update the example

#include <qcor_qft>

using QPEOracle = CallableKernel<qreg, int>;

using QPEOracleSignature = KernelSignature<qreg, int>;

__qpu__ void QuantumPhaseEstimation(qreg q, QPEOracle oracle) {

__qpu__ void QuantumPhaseEstimation(qreg q, QPEOracleSignature oracle) {

  // We have nQubits, the last one we use

  // as the state qubit, the others we use as the counting qubits

  const auto nQubits = q.size();

  for (auto i : range(nCounting)) {

    const int nbCalls = 1 << i;

    for (auto j : range(nbCalls)) {

      int ctlBit = i;

      // Will be fixing this parent_kernel thing...

      oracle.ctrl(ctlBit, q, state_qubit_idx);

      oracle.ctrl(i, q, state_qubit_idx);

    }

  }

int main(int argc, char **argv) {

  auto q = qalloc(4);

  // very cool, implicit conversion works here

  // so you can just pass the kernel function

  QuantumPhaseEstimation(q, compositeOp);

  q.print();

}