> This should be a FAQ.
>

Since we're talking of 10+ lines of code and only one case among many
possible (you might also want to do something fairly similar, but not quite
the same, as iterating over all words or characters in a file, doing
something else than counting, etc.), I would rather see it implemented in a
library as combinator. What I have in mind is a function that goes over a
file and invokes some user code on each block of
bytes/characters/lines/words/... The points of customization would be:
* how to detect the start and end of block
* routine to pass the blocks to

Then, on top of this combinator, build block-specific ones: for byte, char,
line, word blocks. Also make it possible to customize buffering behavior.

Being new to OCaml, I'm interested in comments - is what I suggest a good
idea? If yes, why hasn't anyone implemented it yet? One could argue that
it's trivial and can be implemented in each use case anew, but among 5
different solutions posted so far, each has its own problems, besides the
supposedly ideal 5-th -- I'd take this as an indication that, although
simple, it's not really trivial to write this thing.