[Haskell-cafe] adjoint of coproduct & diagonal

Jason Dusek jason.dusek at gmail.com
Sat Aug 2 21:22:50 EDT 2008

  I'm trying to figure out the adjunction diagrams for the
  adjunction where the diagonal functor is right adjoint to the
  coproduct functor. I'm |almost done|, but the co-unit has me
  stumped, because I can't figure out how the arrow at the top
  can be unique -- it seems it could be either one of:

    i_1 . [f,g]
    i_2 . [f,g]

      i_1, i_2 : C -> C+C
      f : A -> C
      g : B -> C

  The net effect of [id,id] on the right is to blur out the
  distinction. On #haskell, someone suggested there is a
  constraint I am missing; I've poked around for a day and still
  can't figure it out.


 |almost done|

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