G.Gonzales, Comonad Challenge Exercise

[sassa_nf]

http://www.haskellforall.com/2013/02/you-could-have-invented-comonads.html
Challenge Exercise: Prove that our original implementation of up' does not play nice with extend. In other words, find a counter-example that proves the following

Comments

[zeit_raffer]

'undefined' and 'seq' always break things

[sassa_nf]

Yes, but in that article Mr. Gonzales is looking at which of the implementations is "better". Ie in the context it would mean one of the implementations "behaves well" with extend, the other one doesn't, and this equation is seen as the decider.