int checkconsistency {

  // Checks that the diagram is a DFA.

  // Return codes:
  // -1  Missing initial or final state
  //  0  Array is consistent
  // >0  State ID of first detected inconsistent state.

  CArray <transitionType*,transitionType*> TransitionTypes = CCanvas.AllType;
  CArray states_array = CCanvas.getAllStates();

  int initial = 0;  // Number of initial states
  int final = 0; // Number of final states

  foreach (currentState) in (states_array) 
  {
    CArray outTransitions = currentState.output;
    CArray outTranTypes;
    foreach (outTransition) in (outTransitions)
    {
      // Get types for each transition
      CArray types = outTransition.type;
      foreach (Ttype) in (types) 
      {
        if (outTranTypes contains Ttype)
        {
          // ERROR: Two identical transition types from same state. Inconsistent.
          return currentState.ID;
        }
        else {
          push(outTranTypes,Ttype);
        }
      }
      if (outTransition.fromStateID == outTransition.toStateID )
      {
        // ERROR: Reflexive state. Inconsistent.
        return currentState.ID;
      }
    }

    // Now compare two arrays: outTranTypes for currentState and TransitionTypes.
    //
    if (sizeof(outTranTypes) == sizeof(TransitionTypes)) {
      foreach (item) in (outTranTypes) {
        if (transition is not in TransitionTypes array)
        { 
          // ERROR: Unlisted transition. Inconsistent.
          return currentState.ID;
        } 
      }
    else {
      // ERROR: Number of transition types does not match. Inconsistent.
      return currentState.ID;
      }

    // Increment initial or final counts, check if too many

    if (currentState.status == 1 || currentState.status == 3)
    {
      initial++;
      if (initial > 1)
      {
        // ERROR: Two initial states. Inconsistent.
        return currentState.ID;
      }        
    }
    if (currentState.status == 2 || currentState.status == 3)
    {
      final++;
      if (final > 1)
      {
        // ERROR: Two final states. Inconsistent.
        return currentState.ID;
      }        
    }

  }

  if (initial != 1 || final != 1)
  {
    // Should be 0 in this case. Insufficient initial/final states.
    return -1;
  }
  else
  {
    // It's consistent. Congratulations. I'll give you a zero-shaped cookie.
    return 0;
  }
}