The Gleason-Prange theorem

The Gleason-Prange theorem describes a nontrivial automorphism of an extended quadratic residue code. By using the Fourier transform in an appropriate extension field, methods of digital signal processing are used to make the proof transparent and the automorphism intuitive. The theorem is proved both in a field of characteristic tow and in an arbitrary field and is stated simply as a general property of the discrete Fourier transform. >