2017-06-08 13:52:58 +0200 asked a question Creating user-defined rings. I want to create rings of the form {-(p-1)/2, ... , 0, ... , (p-1)/2} , but Zmod(p) gives {0, ... , p-1}. How can this be done? Is there a way I could create custom-rings from lists? Like range(-d. d+1) ?