[Haskell-cafe] adjoint of coproduct & diagonal

Jason Dusek jason.dusek at gmail.com
Sun Aug 3 02:40:10 EDT 2008

Derek Elkins <derek.a.elkins at gmail.com> wrote:
> [id,id] is the counit.
> [id,id] : C+C -> C
> Given a function f : A+B -> C there exists a unique function
> f* : (A,B) -> (C,C) that is a pair of functions
> h : A -> C and k : B -> C such that
> [id,id] . h+k = f.

  This f is what I have labelled [f,g] (or f+g) in the diagram I
  linked to, right?

  In that case h and k are just f and g, respectively, and the
  unique arrow that goes from A+B to C+C is f+g -- but that
  would make C+C just the same as C.


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