?
Solved

looking for something like a std::map

Posted on 2001-09-11
9
Medium Priority
?
672 Views
Last Modified: 2013-12-14
I am looking for a stl class which is like a std::map, but which doesn't sort the elements, i.e. like a vector of pairs, but where you can do a find like you can with a std::map. Obviously I am aware that I could write a class that is a vector of pairs with a find method, however there is probably a stl class that does exactly what I want already.
0
Comment
Question by:duncanlatimer
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
  • 3
  • 2
  • +1
9 Comments
 
LVL 30

Expert Comment

by:Axter
ID: 6474342
You can try using a hash_map class.
hash_map is not part of the official C++ standards, but you can download a free copy of the class if you're intererested.
0
 
LVL 9

Expert Comment

by:jasonclarke
ID: 6474362
I don't think there is such a thing.

Maybe multimap is what you want, it allows you to have multiple values with the same key.  It is sorted, however.

If sorting is a problem you could also try the hash associative container that is part of the SGI (and STLport) implementation of the STL.

See: http://www.sgi.com/tech/stl/HashedAssociativeContainer.html

for details and www.stlport.org for the stlport download.

However, you should note that the entire point of these associative containers is to provide fast access by key value - so the classes need some way to store key values for efficient lookup.
0
 
LVL 9

Expert Comment

by:jasonclarke
ID: 6474367
Didn't see your comment there Axter.
0
What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

 

Author Comment

by:duncanlatimer
ID: 6474420
As the order of the elemets in a hash_map are not guaranteed this will probably not work for me. I need to be able to retrieve the elements in the same order that I loaded them. And I also need to be able to do a find on a key.
0
 

Author Comment

by:duncanlatimer
ID: 6474444
I envisage that the container I am after has two different types of iterators, one type providing sorted access for finds etc, the other providing load sequence order access.
0
 
LVL 9

Expert Comment

by:jasonclarke
ID: 6474448
The solution may well depend then on what your main concern is.  If speed of lookup is very important then you might consider storing maybe a vector and a map, maybe they could contain pointers to stored data structures, or maybe the vector could just contain key values.

i.e. something like:

vector<string> keyVector;
map<string,value>  mymap;

then you could implement a 'get by index' something like this:

value getByIndex(size_t index) const
{
    return mymap[keyVector[index]];
}

(you might want to change it add some error checking!).
0
 
LVL 30

Accepted Solution

by:
Axter earned 400 total points
ID: 6474459
You can use a vector pair, and search for your data using the find_if function with a Predicate.

Example code:
#include <iostream>
#include <set>
#include <string>
#include <vector>
#include <algorithm>

class FindName {
public:
     FindName(std::string Name) : m_Name(Name){}
     bool operator()(const std::pair<std::string,std::string> &Src)
     {
          return (Src.first == m_Name);
     }
     std::string m_Name;
};

int main(int argc, char* argv[])
{
     std::vector<std::pair<std::string,std::string> > myset;
     myset.push_back(std::pair<std::string,std::string>("Sue", "girl"));
     myset.push_back(std::pair<std::string,std::string>("Tom", "boy"));
     myset.push_back(std::pair<std::string,std::string>("Kim", "girl"));
     myset.push_back(std::pair<std::string,std::string>("Jack", "boy"));
     myset.push_back(std::pair<std::string,std::string>("Betty", "girl"));
     myset.push_back(std::pair<std::string,std::string>("Jill", "girl"));
     myset.push_back(std::pair<std::string,std::string>("Bob", "boy"));
     myset.push_back(std::pair<std::string,std::string>("David", "boy"));
     myset.push_back(std::pair<std::string,std::string>("Candy", "girl"));
     std::vector<std::pair<std::string,std::string> >::iterator  who =
          std::find_if(myset.begin(),myset.end(),FindName("David"));
     if (who != myset.end())
     {
          std::string MaleOrFemale = who->second;
          std::cout << "David is a " << MaleOrFemale << std::endl;
     }
     return 0;
}


0
 
LVL 6

Expert Comment

by:Triskelion
ID: 6474509
MFC has a CMap class
0
 

Author Comment

by:duncanlatimer
ID: 6474567
I am trying to avoid MFC and Axter's solution is exactly what I need so...
0

Featured Post

Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

C++ Properties One feature missing from standard C++ that you will find in many other Object Oriented Programming languages is something called a Property (http://www.experts-exchange.com/Programming/Languages/CPP/A_3912-Object-Properties-in-C.ht…
Many modern programming languages support the concept of a property -- a class member that combines characteristics of both a data member and a method.  These are sometimes called "smart fields" because you can add logic that is applied automaticall…
The viewer will learn how to use and create new code templates in NetBeans IDE 8.0 for Windows.
The goal of the tutorial is to teach the user how to use functions in C++. The video will cover how to define functions, how to call functions and how to create functions prototypes. Microsoft Visual C++ 2010 Express will be used as a text editor an…
Suggested Courses

770 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question