RE: [boost] Ongoing MPL Formal Review

From: Anthony Williams (anthwil_at_[hidden])
Date: 2002-07-31 07:47:29

Firstly, I think the MPL is a powerful, useful library that should
definitely be accepted into boost.

The biggest problem I have is with the lack of documentation, particularly
for bind/lambda, though I know that Aleksey is working on that.

To add my twopennorth to the discussion of the container/algorithm
separation, it can be important to know the structure of the container when
writing the algorithm, even if it could be written using iterators. Take,
for example, the quick-sort implementation I submitted recently. It uses
pop_front and push_front, which would actually prevent its use on containers
that only supply push_back/pop_back. I could have written it to use insert
and erase, but to do so would hide the inefficiencies so generated --- if a
container only supplies push_back/pop_back, then it is better to rewrite
sort to work backwards, rather than use insert/erase. Also, it always uses
the first element as a pivot, because removing elements from the middle of a
list is inefficient, and removing elements from the front of a container
that supports efficient removal from the middle is no worse. However,
rewriting it to choose a better pivot for containers where removing elements
from the middle is efficient, would improve overall performance by avoiding
worst-case scenarios.

As for "metafunction class" vs "quoted metafunction", I would prefer
something that more clearly meant "a class with a member template apply".
"quoted metafunction" implies you can do quote<my_metafunction>, which you
can't (I know lambda almost gives you that). "metafunction class" is OK, but
possibly slightly confusing.

Anthony