Martin reacts to my non-answer:

Am 04/26/2015 um 05:28 PM schrieb Jerzy Karczmarczuk:

...
and GHCi says:

*Main> ex10
*** Exception: Prelude.head: empty list

This is because I have commented out two corner cases in tBind, to make sure it's not them. Remove the comments and
it'll work

Martin I sent you a private follow-up. I repeat it here.

I uncommented those lines.
Your program goes until the end of the list, and returns the last element (modified). The form

tBind tpr f
...
(tTail tpr `tBind` f)

loops until ...

Now, I know about laziness... It seems that it doesn't help. Most probably your hd is simply empty, and the tail gets stuck in an idle loop.

Jerzy Karczmarczuk