clear method

void clear()

Free up memory

Implementation

clear() {
  if (_pExpression == 0) throw ClearedExpressionException();
  FlutterExprtkPlatform.instance.clear(_pExpression);
  _variableNames
      .forEach((key, ptr) => FlutterExprtkPlatform.instance.free(ptr));
  _pExpression = 0;
}