Full example

namespace Bell {
  open Microsoft.Quantum.Canon;
  open Microsoft.Quantum.Intrinsic;

  operation SetQubitState(desired : Result, target : Qubit) : Unit {
      if desired != M(target) {
          X(target);
      }
  }

  @EntryPoint()
  operation TestBellState(count : Int, initial : Result) : (Int, Int) {

      mutable numOnes = 0;
      use qubit = Qubit();
      for test in 1..count {
          SetQubitState(initial, qubit);
          let res = M(qubit);        

          // Count the number of ones we saw:
          if res == One {
                set numOnes += 1;
          }
      }

      SetQubitState(Zero, qubit); 

  // Return number of times we saw a |0> and number of times we saw a |1>
  Message("Test results (# of 0s, # of 1s): ");
  return (count - numOnes, numOnes);
  }
}