Difference between revisions of "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
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==Definition==
 
==Definition==
 
Given a [[set]], {{M|X}}, there is a ''free'' [[monoid]], {{M|(F,*)}}{{rAAPAG}}.  
 
Given a [[set]], {{M|X}}, there is a ''free'' [[monoid]], {{M|(F,*)}}{{rAAPAG}}.  

Revision as of 13:58, 20 July 2016

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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, [ilmath]X[/ilmath], there is a free monoid, [ilmath](F,*)[/ilmath][1].

  • The elements of [ilmath]F[/ilmath] are all the finite tuples, [ilmath](x_1,\ldots,x_n)[/ilmath] (where [ilmath]x_i\in X[/ilmath])
  • The monoid operation ([ilmath]*:F\times F\rightarrow F[/ilmath]) is concatenation:
    • [ilmath]*:((x_1,\ldots,x_n),(y_1,\ldots,y_n))\mapsto(x_1,\ldots,x_n,y_1,\ldots,y_n)[/ilmath]
  • The identity element of the monoid is:
    • [ilmath]e=()[/ilmath] - 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. Abstract Algebra - Pierre Antoine Grillet

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