Homotopy Type Theory
monoid > history (Rev #13, changes)
Showing changes from revision #12 to #13:
Added | Removed | Changed
Contents
Definition
A monoid consists is of aset with an element and a function such that
A type ,
A basepointfor all ,
A binary operationfor all , , and ,
- A contractible left unit identity
- A contractible right unit identity
- A contractible associative identity
- A 0-truncator
Properties
We define the binary operation as
Monoid homomorphisms
A monoid homomorphism between two monoids and consists of
- A function such that
- The basepoint is preserved
- The binary operation is preserved
For any function
the contractible left unit identity is preserved:
because
is contractible. Likewise, for any function
the contractible right unit identity is preserved:
because
is contractible, and for any function
the contractible associative identity is preserved:
because
is contractible. Finally, the 0-truncator is always preserved in a function between two sets.
Monoid isomorphisms
A monoid isomorphism between two monoids and consists of
- a monoid homomorphism
- a monoid homomorphism that is an inverse function of .
Examples
-
Every contractible magma is a monoid.
-
The integers are a monoid.
-
Given a set , the type of endofunctions has the structure of an monoid, with basepoint , operation function composition.
See also
References
Revision on June 13, 2022 at 22:33:54 by
Anonymous?.
See the history of this page for a list of all contributions to it.