Dual of codes over finite quotients of polynomial rings

Let A=F[x]〈f(x)〉, where f(x) is a monic polynomial over a finite field F. In this paper, we study the relation between A-codes and their duals. In particular, we state a counterexample and a correction to a theorem of Berger and El Amrani (2014) [3] and present an efficient algorithm to find a system of generators for the dual of a given A-code. Also we characterize self-dual A-codes of length 2 and investigate when the F-dual of A-codes are A-codes.