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From: Victor A. Wagner, Jr. (vawjr_at_[hidden])
Date: 2002-07-25 01:15:58

I've noticed in our coding, we sometimes need a comparison operator that
works on just a single element in a struct, instead of the "entire
struct". If we need to sort the container using just this "key"; we, of
course, write the comparison function/functor and then:

std::sort(c.begin(), c.end(), ourfunction);

I decided to write a couple templates and helper functions called (the ones
you'd use) less_element() and greater_element().

if then we have, e.g. :
struct person{
std::string firstname;
std::string lastname:
....other stuff

and a container of them, we can:

std::sort(c.begin(), c.end(), less_element(firstname));
std::sort(c.begin(), c.end(), greater_element(lastname));

I'm sorry to be so wordy, but neither of us in this group has ever worked
in a large (>4) staff using C++, so maybe we're just missing a whole lot
(discussion of wisdom of public variables aside...we use them), or these
may be useful to others also.

We'd be happy to clean them up and boostify them if there is interest.
Victor A. Wagner Jr.
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