Tuple<> looks like the simplest functor by just wrapping a value. It is most close to the [Identity functor of Haskell](http://hackage.haskell.org/package/transformers-0.4.3.0/docs/Data-Functor-Identi

A simple functor in DotNet category is Lazy<>. Its Select functions can be easily implemented:

A F: C → D is a structure-preserving ) from category C to category D:

An individual monoid (T, ⊙, I) can be a category M:

A ), denoted a 3-tuple (M, ⊙, I), is a set M with

This post and the following posts will introduce category theory and its important concepts via C# and LINQ, including functor, applicative functor, monoid, monad, etc. Categories were first introduce

p is the ) of function F :

is an with minimum elements but still [Turing-complete](ht