list.push_back() problem

[lare26]

I am trying to create a list of rooms to add an location number. But i am getting errors. Why am i getting those errors?

code:

list<Room> room;
    list<Room>::iterator pcit;
    int i = 0; //help to add a diiferent number for each room
    for(list<Room>::iterator pcit = room.begin(); pcit !=room.end(); ++pcit)
    {
        room.push_back(); // add a room
        int num = 1000 +i; // first location will be 1000, then 1001 etc...
        room[pcit].setlocation(num); // set the location number of each room
        ++i;
    }

errors:

F:\CodeBlocks-Programs\QuickRPG\main.cpp||In function 'int main()':|
F:\CodeBlocks-Programs\QuickRPG\main.cpp|303|error: no matching function for call to 'std::list<Room, std::allocator<Room> >::push_back()'|
f:\programs\codeblocks\mingw\bin\..\lib\gcc\mingw32\4.4.1\include\c++\bits\stl_list.h|919|note: candidates are: void std::list<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = Room, _Alloc = std::allocator<Room>]|
F:\CodeBlocks-Programs\QuickRPG\main.cpp|305|error: no match for 'operator[]' in 'room[pcit]'|
||=== Build finished: 2 errors, 0 warnings ===|

I edited out errors I can fix on my own.

[ResidentBiscuit]

Push_back() has a parameter. The error message says this.

[coder777]

The first error:
the function push_back() needs an actual object that it can push back.

The actual object in your case would be *pcit (Note the *)


The second error:
You cannot use the iterator within the [] operator. You can use the -> operator of the iterator, like so pcit->setlocation(num);

But that's likely not what you want. To access the object that you recently push_back() you can use back(), like so room.back().setlocation(num);

For more function of the list class look here http://www.cplusplus.com/reference/stl/list/

[lare26]

but how would I have to set it up to work right? I have no idea what the error means. I tried this:

list<Room> room;
    list<Room>::iterator pcit;
    int i = 0;
    for(list<Room>::iterator pcit = room.begin(); pcit !=room.end(); ++pcit)
    {
        int num = 1000 +i;
        room.push_back(room.setlocation(num));
        ++i;
    }

and got this error:

F:\CodeBlocks-Programs\QuickRPG\main.cpp|304|error: 'class std::list<Room, std::allocator<Room> >' has no member named 'setlocation'|

EDIT:
coder777,
Oh my bleep! I tried it and it worked! Thanks. This is what i did:

list<Room> room;
    list<Room>::iterator pcit;
    int i = 0;
    for(list<Room>::iterator pcit = room.begin(); pcit !=room.end(); ++pcit)
    {
        int num = 1000 +i;
        room.push_back(*pcit);
        pcit->setlocation(num);
        room.back().setlocation(num);
        //room.push_back(room.setlocation(num));
        ++i;
    }

Is that what you meant? I think I understand the use. But I will have to re-read the <list> article and the code I'm now using. Thanks again, coder777. :)

[lare26]

I think I messed something up. I want to setup doors and where they lead to. but I amhaing trouble accessing my rooms member functions to do so:

int main()
{
    list<Room> room;
    list<Room>::iterator pcit;
    int i = 0;
    for(list<Room>::iterator pcit = room.begin(); pcit !=room.end(); ++pcit)
    {
        int num = 1000 +i;
        room.push_back(*pcit);
        pcit->setlocation(num);
        room.back().setlocation(num);
        ++i;
    }
    Room[0]->setdoore(true); // sets east door to exist
    Room[0]->setide(1002); // sets east door id to go to room 1002 

What am I not understanding about lists that I can't do it?

[coder777]

Are you sure that you want to take an element of the list and push back to that list? It will cause an infinite loop since there will always be an element to push back.

I guess what you want is this:

list<Room> room;
    list<Room>::iterator pcit;
    int i = 0;
    for(list<Room>::iterator pcit = room.begin(); pcit !=room.end(); ++pcit)
    {
        int num = 1000 +i;
        // This will cause an infinite loop: room.push_back(*pcit);
        pcit->setlocation(num);
        // Without push_back you don't need this: room.back().setlocation(num);
        //room.push_back(room.setlocation(num));
        ++i;
    }

EDIT: You can do that without iterator:

for(list<Room>::size_type i = 0; i < room.size(); ++i)
    {
        pcit->setlocation(1000 +i);
    }

[lare26]

I guess I am trying to setup a number of rooms(say 10 of them). And then I will go back and manually setup the doors and what-not to each room.

Intended program progression:
1-> make several rooms which are pre-set with an identifying number
2-> set doors to exist in each room, manually
3-> set where each door of each room leads to when it is used

I know it will be simpler(or so I thought) to use <list> and a for loop to create the rooms and identify them. I know(I think) I will have to set each rooms other characteristics myself. I didn't even want to try to create a list of rooms and characteristics in a text file. Not enough Tylenol in the house for that.

Is my thinking on the way to do this right?

[ne555]

¿Are you just smashing the keyboard?

int main()
{
    list<Room> room;//an empty list
    list<Room>::iterator pcit;
    int i = 0;
    for(list<Room>::iterator pcit = room.begin(); pcit !=room.end(); ++pcit) //never executes (if it does, infinite loop because the list is growing)
    {
        int num = 1000 +i;
        room.push_back(*pcit); //copying rooms
        pcit->setlocation(num);
        room.back().setlocation(num);
        ++i;
    }
    Room[0]->setdoore(true); // Room is a class, not an object
    Room[0]->setide(1002);

I am trying to create a list of rooms to add an location number

for( size_t K=0; K<42; ++K)
  room.push_back( Room(1000+K) );

Dunno how your map is, but you could loop againg to set the doors.