Cartesian closed categories are distributive
  A folklore result in category theory is that a (weakly) Cartesian closed category with finite co-products is distributive. Usually, the proof of this small result is carried on using the fact that the exponential functor is right adjoint to the product functor. And, since functors having a right adjoint preserve co-limits, the result follows immediately. But, when we try to explicitly construct the arrows, things become a bit more involved. In rare cases, it is pretty useful to have the exact arrows that make this isomorphism to hold. The purpose of this note is to develop the explicit proof with all the involved arrows constructed in an explicit way. 
Marco Benini
math.CT