printing a struct with a map in it - c++

Question

Ok I am having trouble printing the values in my list of structs. The normal way of printing a list (with the iterator) is not working. This is my code of me reading in a file into my list.
struct Edge{
map<char, string> edge;
int weight= -1;
Edge(){};
Edge(char v, string e, int w){
edge.insert(pair<char,string>(v,e));
weight = w;
}
};
int main(){
list<Edge> edges;
//Read in file//
string line;
char start;
vector<string> tokens;
if(!file.is_open()){
cout<<"Could not open file\n";
}else{
while(getline(file,line)){
tokens.clear();
start = line.front();
istringstream iss(line);
copy(istream_iterator<string>(iss),
istream_iterator<string>(),
back_inserter<vector<string>>(tokens));
for(int i = 1; i<tokens.size(); i+=2){
//cout << "Position: " <<i << " = " << tokens.at(i) <<endl;
//insert into edges list.
Edge e = Edge(start, tokens.at(i), stoi(tokens.at(i+1)));
edges.push_back(e);
}//end for
}//end while
}//end if-else
return 0;
}//end main
The vector tokens is read in properly. I checked it with the commented out cout.
The file is a graph file with the first element the start vertex and the rest of the line is formatted with the end vertex of the edge and the weight of that edge.
For example:
1 2 3 4 5
Would mean edge (1,2) has a weight of 3 and edge (1,4) has a weight of 5.
I don't know if I read in my list properly because I can't figure out how to print it out. How would I print out my list edges ?
Or is there a better way to set up my struct? Perhaps another struct for the edge and then a struct with the edge and weight?
Printing tried that won't work. The syntax doesn't even work. :(
The regular way to print a list. But doesn't like it since I have a struct list.
list<Edge>::iterator it;
for(it=edges.begin(); it!=edges.end(); it++){
cout << *it <<endl;
}//end for
And this was what I found when I searched. This is what I found.
C++ How to loop through a list of structs and access their properties
This is my attempt.
//inside main
list<Edge>::iterator it;
for(int i = 0; i<edges.size(); i++){
for_each(edges.begin(), edges.end(), printEdges);
}//end for
//outside main
void printEdges(Edge &data){
cout << "( " << data.edge << " )"
<< ": Weight = " << data.weight <<endl;
}//end printEdges
Thank you.

Answer 1

Update to comment:
friend std::ostream& operator<<(std::ostream& os, Edge const& edge)
{
os << "Edge { weight:" << edge.weight << " {\n";
for(edge_map::const_iterator it=edge.edge.begin(); it!=edge.edge.end(); ++it)
{
os << "{ '" << it->first << "', \"" << it->second << "\" } ";
}
return os << "\n}";
}
Should get you started.
it's int main, not void main
it's weight = w;, not weight = w.
You need to increment the loop variable. i+2 has no effect. Did you mean i+=2?
If you did, the loop condition should be fixed to avoid out-of-bounds addressing:
for(size_t i = 1; i+1<tokens.size(); i+=2){
note the use of size_t to avoid mixed signed/unsigned comparison
the Edge constructor should initialize weight
If you need //crutch comments, your code should be more legible :_)
Consider using a parser to read your input. You severely lack input validation, format flexibility and error handling.
Oh, don't use using namespace std
Here's an attempt at fixing some of the issues:
#include <string>
#include <map>
#include <list>
#include <vector>
#include <iostream>
#include <iterator>
#include <sstream>
#include <fstream>
#include <algorithm>
struct Edge{
typedef std::map<char, std::string> edge_map;
edge_map edge;
int weight;
Edge() : edge(), weight(0) {};
Edge(char v, std::string e, int w) : edge(), weight(w)
{
edge.insert(std::pair<char,std::string>(v,e));
weight = w;
}
friend std::ostream& operator<<(std::ostream& os, Edge const& edge)
{
os << "Edge { weight:" << edge.weight << " {\n";
for(edge_map::const_iterator it=edge.edge.begin(); it!=edge.edge.end(); ++it)
{
os << "{ '" << it->first << "', \"" << it->second << "\" } ";
}
return os << "\n}";
}
};
int main()
{
std::list<Edge> edges;
std::string line;
std::vector<std::string> tokens;
std::ifstream file("input.txt");
if(!file.is_open()){
std::cout<<"Could not open file\n";
}else{
while(std::getline(file,line)){
tokens.clear();
char start = line.front();
std::istringstream iss(line);
std::copy(std::istream_iterator<std::string>(iss),
std::istream_iterator<std::string>(),
std::back_inserter<std::vector<std::string>>(tokens));
for(size_t i = 1; i+1<tokens.size(); i+=2){
Edge e = Edge(start, tokens.at(i), stoi(tokens.at(i+1)));
edges.push_back(e);
}
}
}
}