A hierarchy for circular codes
We first prove an extremal property of the infinite Fibonacci word : the family of the palindromic prefixes {} of is not only a circular code but “almost” a comma-free one (see Prop. 12 in Sect. 4). We also extend to a more general situation the notion of a necklace introduced for the study of trinucleotides codes on the genetic alphabet, and we present a hierarchy relating two important classes of codes, the comma-free codes and the circular ones.