code: func makeSwap(size int64) executionFunc {
  	// switch n + 1 otherwise n would be swapped with n
  	size++
  	return func(pc *uint64, interpreter *EVMInterpreter, contract *Contract, memory *Memory, stack *Stack) ([]byte, error) {
  		stack.swap(int(size))
  		return nil, nil
  	}
  }
docs: // make swap instruction function