Free monoid generated by

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Be sure to check Discussion of the free monoid and free semigroup generated by a set, as there are some things to note

Definition

Given a set, X, there is a free monoid, (F,)[1].

  • The elements of F are all the finite tuples, (x1,,xn) (where xiX)
  • The monoid operation (:F×FF) is concatenation:
    • :((x1,,xn),(y1,,yn))(x1,,xn,y1,,yn)
  • The identity element of the monoid is:
    • e=() - the "empty" tuple.

The proof that this is indeed a monoid is below

Examples

  • This page can be considered an element of the monoid generated by the alphabet (union all the symbols too)

Proof that this is indeed a monoid

  1. Associativity is trivial
  2. Identity element being an identity element is trivial

(These might be good "low hanging fruit" for any newcomers)

References

  1. Jump up Abstract Algebra - Pierre Antoine Grillet

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