0

I'm playing around with some boost containers, but I recently came a blockade as I can't seem to define multi_index_container correctly. I'm following an example i grabbed offline but it still gives me and error message:

struct boost::multi_index::global_fun<const node&, int, <error-constant>>

Error: Expression must have a constant value

Here is my declaration:

#define _CRT_SECURE_NO_DEPRECATE
#define _SCL_SECURE_NO_DEPRECATE
#include <boost/config.hpp>

#include <string>
#include <iostream>

#include <boost/multi_index_container.hpp>
#include <boost/multi_index/key_extractors.hpp>
#include <boost/multi_index/hashed_index.hpp>
#include <boost/multi_index/global_fun.hpp>
#include <boost/multi_index/ordered_index.hpp>
using namespace boost::multi_index;

struct node
{
    node(std::string da, int in) {
        data = da;
        numerical = in;
    };
    std::string data;
    int numerical;
};

int main()
{
    typedef multi_index_container<
        node,
        indexed_by<
            hashed_unique<
                member<node,std::string, &node::data>>,
            ordered_non_unique<
                global_fun<const node&, int, node::numerical>> //right here, the value numerical errors
            >
        > node_type;



}

I have a hunch that I'm not including a file for this, but I can't find a solution.

Syntactic Fructose
  • 18,936
  • 23
  • 91
  • 177
  • `node::numerical` is obviously not a global function but a member. Wht are you trying? – pmr May 14 '13 at 14:14

1 Answers1

1

This should do it:

typedef multi_index_container<
  node,
  indexed_by<  hashed_unique< member<node,std::string, &node::data> >
             , ordered_non_unique< member<node, int, &node::numerical> >
            >
  > node_type;

global_fun expects, well, a gloabl function. &node::numerical is a member just like &node::data. You can of course write a function that accepts a node and extracts it, but why would you?

You are also missing the member.hpp include.

pmr
  • 58,701
  • 10
  • 113
  • 156