Bidirectional range dilemma

[bearophile]

Peter Alexander:

> (or equivalently, one range with an iteration policy).

If no other better solution is found, one range with an iteration 
policy is acceptable, in my opinion.

(By the way, what's the API of your functions? In similar 
generators I usually add a boolean doCopy template argument, that 
defaults to true. If it's true, the generator yields different 
buffers, otherwise it yields always the same modified buffer. 
This allows to have both convenience & safety on default, and 
speed on request).

Bye,
bearophile