Limits, colimits, and (a very limited look at) their usefulness in programming

Teacher, author and professor extraordinaire (disclaimer: I'm not being sarcastic, I really highly respect this man) Robert Harper posted a high-flying, chock-full of much more information that was used to write-it article on his blog: The Point of Laziness

In it, he tries to once more expound on why the Haskell programming language is unfit for teaching introductory FP. Once more, he has so much to say on the matter, that he winds up only telling that he has a lot to say. Pretty much, if you understand his arguments, you already know them, but fortunately, there are other readers who comment, and draw out more info to better understand what he is particularly speaking about.

Jeremy Gibbons, in a thankfully reliable style, saved the day, with this lovely sum-up on reddit:
"Due to the way Haskell allows ⊥/'undefined' to inhabit all types, the projection/injection functions that
define how a product/sum type behaves are not sufficient to uniquely identify the value of interest." (my interpretation; please castigate me, and not him.

It's slow-going, but learning is happening...I think.