Generalizations
A constacyclic code is a linear code with the property that for some constant λ if (c1,c2,...,cn) is a codeword then so is (λcn,c1,...,cn-1). A negacyclic code is a constacyclic code with λ=-1. A quasi-cyclic code has the property that for some s, any cyclic shift of a codeword by s places is again a codeword. A double circulant code is a quasi-cyclic code of even length with s=2.
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