Bill Page <bill.p...@newsynthesis.org> writes:

| One clarification. Actually despite what Gaby wrote in an earlier
| email, I still don't think it is quite correct to claim that a functor
| such as List is an endofunctor, at least not in the category-theoretic
| sense.

Unless, you have a very exotic definition of endofunctor, List(S)
satisfies Type for all S that satisfies Type.  How less "endofunctor"
can that be?

| The reason is that it is defined as follows:
| 
|   List(R:Type): Join(ListAggregate(R), ... )
| 
| The source category of List, i.e. Type, is not the same as the target
| category of List, i.e. Join(ListAggregate(R), ... ).

The target is included in Type, and that is all that is needed to
satisfy the notion `endofunctor'.  Being an endofunctor does not require
surjectivity!

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