Re: std:less

From:
Rolf Magnus <ramagnus@t-online.de>
Newsgroups:
comp.lang.c++
Date:
Mon, 17 Nov 2008 08:53:08 +0100
Message-ID:
<gfr7st$euo$01$1@news.t-online.com>
Mike Copeland wrote:

   How does one use std:less? Specifically, I have a declaration as
follows:
struct ChipRecord // Chip Times record
{
    int bibNum; // Bib #
    long lowStartTime; // Start Time
    long hiStartTime; // Start Time
    long gunTime; // Gun Time, if needed
    long lowFinishTime; // Start Time
    long hiFinishTime; // Start Time
    long netTime; // computed "net" Finish Time
    string entName; // Entrant Name
    string chipId;
    string ctsKey; // City/State abbreviation key
    short entAge; // Age
    char entSex; // Sex code (M/F)
    char entRCode;
} timeWork; // entrant info record
typedef map<string, ChipRecord> CHIPINFO;
CHIPINFO chipInfo;
map<int, ChipRecord>::iterator cIter;

   In the above, the "index" to the objects is numeric (bibNum), and I
wish to assure that (1) no duplicates are stored and (2) I could produce
an ordered listing of all stored data. Since sorting an STL map seems
overly difficult,


std::map works by sorting the elements by key internally. That's what makes
the map find its elements quickly. It's not 'overly difficult' to sort it
in a different way, but rather not possible at all.

is there some way to use the std::less option somehow
to get the data stored sequentially?


The map uses std::less on the key only.

   If so, how do I use this option? If not, what might I do? TIA


If you want to change the sort order, a map isn't the right container. You
could use another container like std::vector. If it's sorted, you can use
std::binary_search to find elements quickly.

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