cartesian, but not cartesian closed

Turns out a category can be "cartesian" without being "cartesian closed".
If it was closed, the category would also have exponentials (basically ArrowApply), which we don't support.

See the definition of a cartesian category on nLab [1], and Robert Harper's explanation of "cartesian" vs "closed".

[1] http://ncatlab.org/nlab/show/cartesian+monoidal+category
[2] http://www.youtube.com/watch?v=3JHTb6b1to8&t=9m30s