AH that was my problem, totally forgot about that. Also i tried to make them all 0, but that wouldnt work either. But i forgot that it FIRST substracts from the value, and only after that checks. Hence my problem.
And about the tail, i know that i didnt have it implented yet, i wanted to make the movement work first .
So now the tail!

Ok the tail works great, my only problem is the collision checking,

i use

while(snake.Dead() == false){
the functions to run the game are here
}
return 0;

where

bool Snake::Dead(){
return dead
}

However i die instantly!

EDIT:
Nvm, i figured it out. Played a bit with the code, came to an understanding that the snakes head is a structure as well. And made a startup timer.
So now the engine is done. Thank you really much! Youve helped me develop a simple snake game, and gave me a base understanding of how iterator work.

Still, even though this is done, why didnt my old code work? (other then the fact i used +1 on the wrong location)

Kind regards, ELmar

The rest is in my first post.
I know, i only checked it for 100 segments, but i could've changed that (for example by making a bigger array and copying all the positions in that). Or i could've made it with a vector.

EDIT
Also i have a question about the structure declared in the class. So i want to make it multiplayer for example. Then ill have to check if the player 2 head x and y coordinates dont touch that of player 1. THat is no problem. But then ill need another for statement witht the iterator, and have no clue how to do this.
This is what i had in mind:

I know the variables are private, but wouldnt it help if i made them public? that way i can easier check for a collision between tail and the head of another snake.

hmm, the friend one i dont get really. so it grants a class the same permissions as another class? But why would i want that in this case?
The getter,
Yeah that basicly, and then use the collision check i stated in the previous post?
and the first option, this one is not really clear to me. Ill try to play around with it.

Also, isnt this very inefficient? checking for 2 lists if there are any collisions?

Haha, ok so the calculations should be just fine .
Also for the checking part, i dont really see how i can read the values of the structure. Ive added the following functions (as you suggested).

const list<segment>& Body()  
{return body;}
const segment& Head() 
{return head;}

Now to retrieve the values of the following code:

bool CheckForSnakeCollision(const Snake& s1 , const Snake& s2) {
   for (s1.list<segment>::iterator it = s1.body.begin() ; it != s1.body.end() ; ++it) {
      if ((it->x == s2.get_x) && (it->y == s2.get_y)) {
                 return true;}
      }
   return false;
}
//where get_y and get_x:
int Snake::get_x()
{
   return head.x
}
//same goes for get_y, but then returning head.y

But obviously this wont work. I cant seem to find a way to call the first part of the for loop (The iterator part) from another object. Should this be done by getters as well???

Nice!
I have only but 2 questions, its about the functions and the use of objects.
Say ive made the following function:

void showCollision(const Snake& p1, const Snake& p2, const Snake& p3, const Snake& p4, Setup S1)
{
     if(SnakeVsSnake(p1,p2)==1){
        S1.DrawText("Player 2 hit player 1");
        p2.stopMoving();
        }
     else if(SnakeVsSnake(p1,p2)==2){
        S1.DrawText("Player 1 hit player 2");
        p1.stopMoving();
        }
}

Now this works fine! for 1 thing, i cant use p2/p1.stopMoving. This is because we are using a pointer here were we dont need that(right?) and thats also why it IS working for the S1.DrawText(const *char).
However, i only know 1 way to fix this, namely:

void showCollision(const Snake& p1, Snake P1, const Snake& p2, Snake P2, const Snake& p3, Snake P3, const Snake& p4, Sake P4, Setup S1)
{
     if(SnakeVsSnake(p1,p2)==1){
        S1.DrawText("Player 2 hit player 1");
        P2.stopMoving();
        }
     else if(SnakeVsSnake(p1,p2)==2){
        S1.DrawText("Player 1 hit player 2");
        P1.stopMoving();
        }
}

However then we get a code with 9 arguments! where i think only 5 are needed(at max)is there a way to go from const& p1 to p1?
also the error it gives:

main.cpp passing `const Snake' as `this' argument of `bool Snake::stopMoving()' discards qualifiers 

Both of your methods arent working. Ive been looking around a bit, and cant find a proper way to do it.
I found a way that makes an array of new objects

     Snake* myObject[4];
     int i;
     Snake * objectPointer;
     for (i = 0; i < 50; i++)
     {
         objectPointer = new Snake;

     }

But then ill have to copy all the values of the reference object, for a dummy object. and i think this is wasting resources a bit much.
So my guess is that i need to get rid of the constant in order to make my reference object functions work. However i do not know how to easily do this.

Also a total different question, is there a function to draw a string in allegro? Ive been searching a lot lately, but all i can come up with are 2 functions which use const * char. And i cant seem to convert a string to a const char (Or i have to use functions which require runtime librarys, in which case i cant port it to for example linux anymore)

thx

Yeah the 50 was a mistake :p. It was from an example i found.
Ill try and get of the const then .
Also the s.c_str() is not working. Ive tried it before and googled it. But i cannot come up with a solution for that problem. And yes i did include <String> and even <CString> yet no succes!
And i know how to draw a char to the screen, but i want to be able to do it with strings .

also not working = it cant convert const snake to snake*. Thats when using the following code:

Snake *snakes[4] = {p1,p2,p3,p4};