## Langages écrits par un code infinitaire. Théorème du défaut.(French)Zbl 0611.68046

If C is a class of (infinitary) codes, a language X is said to be written by a C-code if there is a $$Y\in C$$ such that $$X\subseteq Y^*$$. The author characterizes infinitary languages written by arbitrary codes, normal codes, prefix codes, and suffix codes. The basis of the quasi-free monoid generated by an infinitary language X written by a code has less elements than X has if X itself is not a code (”Theorem of defect”). A recognizable infinitary language written by a code can also be written by a recognizable code.
Reviewer: M.Armbrust

### MSC:

 68Q45 Formal languages and automata 20M35 Semigroups in automata theory, linguistics, etc. 94A45 Prefix, length-variable, comma-free codes

### Keywords:

infinitary code; infinitary languages; quasi-free monoid