problem defening a map of structs

hello,

I try to define a map of structs.

What I have is this :

Code:

---

#include <iostream>
#include <map>
#include <string>

using namespace std;

int main() {

struct teamstats {
string team_name;
int played_games, point_made, points_against;
}

map<string, struct teamstats> allteams;

}

---

I see now this message :

C:\Users\wobben\Desktop\toernooi\test\main.cpp|14| error: template argument for 'template<class _T1, class _T2> struct std::pair' uses local type 'main()::teamstats'|

Can someone explain what went wrong here ?

Roelof

You should define the struct outside of the main function, with a trailing semi-colon and proper indentation, e.g.,

Code:

---

#include <iostream>
#include <map>
#include <string>

using namespace std;

struct teamstats {
    string team_name;
    int played_games, point_made, points_against;
};

int main() {
    map<string, teamstats> allteams;
}

---

Oke,

Solved,
Now can i test if I can read the data from a file and put it into the struct.

Roelof

Ike,

Last question I hope,

Can I sort the map first on game_points and if there the same on played_games.

Roelof

A map is not meant to be sorted. It simply allows you to map one type to another.

Oke,

Then I have a problem.
The outcome of the reading of the file and processing it , must be sorted so I can make a good ranking.

back to the drawing board.

Roelof

You can use another container. For example, iterate your map, take every element, put it into a vector, sort it, then print your results.

oke,

So read the map teamstats.
Copy everything to a container of vectors and then sort it.

Do I understand you right.
And can a container of vectors be sorted on multiple arguments.
Can I then not using a container of vectors in the first place ?

Roelof

A vector (or any other container that is sortable) can be sorted by multiple values. You decide exactly how to sort it by implementing your operator <.
Could you use it from the beginning? I don't know. I haven't followed what exactly you do.

What I try to do is this.

my struct looks like this :
string team_name
int played_games, game_points, made_points, against_points.

Read a line from a text file.
and put the content of that file to these variables : home_team, away_team, home_score and away_score.

Then test if home_team is not already in the container.
If so do this :
increase played games for that team by 1
look if that team has won , if so increase game_points by 3
increase
Increase made_points and against_points by the score of that game.

The same story of the away_team.

Read the following line and start over again with the home_team.

If the whole file is read to the end.
Sort everything and print it out.

Roelof

Edit :

I see what's the problem is with vector containers.
I don't know how many teams there are so I can't define the container well.
Or make use of resize when finding a new team.

Second problem
I have this code:

Code:

---

#include <iostream>
#include <map>
#include <string>
#include <fstream>

using namespace std;

struct teamstats {
    string team_name;
    int played_games, point_made, points_against;
};

int main() {
    map<string, teamstats> allteams;
    string str,myBuf;

    ifstream a_file ("test.txt");
    a_file >> str ;
    cout << str ;
 return 0 ;
}

---

Why gives cout no output.
The file test.txt exist with one rule.

Roelof

Try adding a few lines to make sure, and read the whole file:

Code:

---

int main() {
    map<string, teamstats> allteams;
    string str,myBuf;

    ifstream a_file ("test.txt");
    if (!a_file.good()) cerr << "File not found!\n";
    while (a_file >> str) cout << str ;

    return 0 ;
}

---

Nb, this method of reading the file chomps newlines.

Quote:

---

You can use another container. For example, iterate your map, take every element, put it into a vector, sort it, then print your results.

---

I actuall do this quite often. Many tests have revealed that iterating a map is far slower than iterating a vector although the code looks identical. Normally I build a vector from the items being used in the map and when the map changes I clear the vector and re-build it from the map. The easiest thing to do is to actually store map iterators in the vector so that when you iterate the vector you gain instant access to the map and it does not require an O(n log n) lookup per item in the vector. This works fine as long as you protect the map and make sure that if something is removed from the map the vector is updated to reflect this. If not you could have invalid iterators in the vector.

store your strings (keys) in a vector, implement a sorting function based on the contents of the map value.

then you can print them in your order, I dont see why its recommended to use another container?

Quote:

---

...dont see why its recommended to use another container?

---

Perhaps to support fast removal and insertion. Vectors are not good for insertion or removal since iterators beyond the point of removal are invalidated.

Oke,

Everyone thanks for the help,
I going to the way of using two maps . One struct for making the ranking and a vector for sorting.

Roelof

Oke,

I try to put in read a string read from a text-file in pieces.

Code:

---

#include <iostream>
#include <map>
#include <string>
#include <fstream>

using namespace std;

struct teamstats {
    string team_name;
    int played_games, point_made, points_against;
};

int main() {
    map<string, teamstats> allteams;
    string str,myBuf, home_team, away_team, home_score, away_score;
    int teller=1  ;

    ifstream a_file ("test.txt");
    if (!a_file.good()) cerr << "File not found!\n";
        while (a_file >> str) {
            int prevPos=str.size()-1;
            int nextPos=str.size()-1;
            while((str.npos != nextPos)&&(nextPos))
                {
                    prevPos=nextPos;
                    nextPos=str.rfind(";", prevPos);
                    if(nextPos==str.npos)
                        {
                            nextPos=0;
                            myBuf= str.substr(nextPos, (prevPos+1));
                        }
                    else
                        {
                            nextPos+=1;
                            myBuf= str.substr(nextPos, (prevPos-nextPos+1));
                            if(nextPos==1)
                            nextPos+=1;
                            nextPos-=2;
                        }
                    }
    return 0 ;
    }
}

---

I add a breakpoint in this rule : myBuf= str.substr(nextPos, (prevPos-nextPos+1));
But when i run the programm the programm doesn't break at the breakpoint

Roelof

Nobody who can tell me what's wrong wit the code.

Roelof

Does it open the file? Ie, no "file not found" error message?
If so, you could post the contents of the file for others to test?

It opens the file.

The contents of the file is one rule"

Code:

---

msk;mac;80;20

---

Roelof

The code works fine for me. It must be your IDE/settings/debugger.

Oke,

Then I have to look into the manual of code::blocks how a breakpoint works.

Roelof

Oke,

Another problem.
I have this code :

Code:

---

#include <iostream>
#include <map>
#include <string>
#include <fstream>

using namespace std;

struct teamstats {
    string team_name;
    int played_games, point_made, points_against, woord;
};

int main() {
    map<string, teamstats> allteams;
    string str,myBuf , home_team, away_team, home_score, away_score;
    int woord=1  ;

    ifstream a_file ("test.txt");
    if (!a_file.good()) cerr << "File not found!\n";
        while (a_file >> str) {
            int prevPos=str.size()-1;
            int nextPos=str.size()-1;
            while((str.npos != nextPos)&&(nextPos))
                {
                    prevPos=nextPos;
                    nextPos=str.rfind(";", prevPos);
                    if(nextPos==str.npos)
                        {
                            nextPos=0;
                            home_team= str.substr(nextPos, (prevPos+1));
                            cout<<"Thuisspelende team :" << home_team;
                        }
                    else
                        {
                            cout << "woord : " << woord ;
                            nextPos+=1;
                            if (woord==1)
                            {
                                away_score = str.substr(nextPos, (prevPos-nextPos+1));
                                cout << "tegengescoord :" << away_score ;
                            };
                            if (woord==2)
                            {
                                home_score = str.substr(nextPos, (prevPos-nextPos+1));
                                cout << "zelfgemaakte doelpunten :" << home_score ;
                            };
                            if (woord==3)
                            {
                                away_team = str.substr(nextPos, (prevPos-nextPos+1));
                                cout << "Tegenpartij :" << away_team ;
                            };
                            if(nextPos==1)
                            nextPos+=1;
                            nextPos-=2;
                        }
                    }
    return 0 ;
    }
}

---

But why does all variables have one value if woord==1 .
I thought that only the expression are carried out when woord=1

Roelof

You set woord = 1 and then it never changes, so woord always == 1. Why do you think it's value should have somehow magically changed?

Hello.

I know that but if woord=1 i put in de code that only away_score get a value.
Why do all the other get values and woord is still 1

Roelof

Quote:

---

Originally Posted by roelof

Why do all the other get values and woord is still 1

---

Let's look at all the places in that code where woord occurs:

Code:

---

    int woord=1  ;

---

Declaration and initialization, woord is assigned a value of 1. Nb. this has nothing to do with the fact that struct teamstats has a member named woord (maybe that is what's confused you?).

Code:

---

                            cout << "woord : " << woord ;

---

Outputing the value of woord will not change it.

Code:

---

                            if (woord==1)
                            if (woord==2)
                            if (woord==3)

---

Testing the value of woord will not change it either.

Woord is not used anywhere else. Hence, woord is always 1. Again, the struct teamstats member "woord" is totally unrelated to "int woord" from main().

Oke,

That word is a member of teamstats is a error of me.

What i mean is that if a run this programm the ouput looks like this :

Woord : 1
home_score : 20
away_score : 20
away_team : 20

When I expect :

Home_score :
away_score : 20
away_team :

That is my question.

Roelof

Hello,

Problem solved on this way :

Code:

---

else
                        {
                            cout << "woord : " << woord ;
                            nextPos+=1;
                            if (woord==1)
                            {
                                away_score = str.substr(nextPos, (prevPos-nextPos+1));
                                cout << "tegengescoord :" << away_score ;
                            };
                            if (woord==2)
                            {
                                home_score = str.substr(nextPos, (prevPos-nextPos+1));
                                cout << "eigen gescoord :" << home_score ;
                            };
                            if (woord==3)
                            {
                                away_team = str.substr(nextPos, (prevPos-nextPos+1));
                                cout << "eigen gescoord :" << away_team ;
                            };
                            woord +=1;
                            if(nextPos==1)
                            nextPos+=1;
                            nextPos-=2;
                        }

---

Roelof