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PO'list iterator not dereferencable'
 

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  1. PO'list iterator not dereferencable'
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    <pre><code> #include &lt;iostream&gt; using namespace std; #include &lt;list&gt; //A queue for the working set //x,y co-ords of the square, path length so far struct square { int x; int y; int path_length; }; list&lt;square&gt; workingset; //A 2D array of ints to represent the board (duplicates list) int board[10][10]; void generatelegalmove(square node, int x_offset, int y_offset); void printboard(); void main() { //Initialises the board int i, j; for (i=0; i&lt;10; i++) { for (j=0; j&lt;10; j++) { board[i][j] = 0; } } //The goal position - a number we will never reach board[8][8] = 1337; bool goal_found = false; //Sets up initial position square temp = {3, 7, 1}; //Put initial position in working set and duplicates list workingset.push_back(temp); board[3][7] = 1; //Loop (until a goal is found) while(!goal_found) { //Get the head node from the working set square nodetocheck = workingset.front(); //Exit if the goal has been found if(board[nodetocheck.x][nodetocheck.y] == 1337) { goal_found = true; break; } //Generate the legal moves generatelegalmove(nodetocheck, -1, 0); //One square to the left generatelegalmove(nodetocheck, 0, -1); //One square up generatelegalmove(nodetocheck, 1, 0); //One square to the right generatelegalmove(nodetocheck, 0, 1); //One square down if(!workingset.empty()) { //workingset.pop_front(); } //End Loop } //Print the Board printboard(); while(true); //Trace back and print Trace back (once implemented) //Print other info } void generatelegalmove(square node, int x_offset, int y_offset) { node.x = node.x + x_offset; node.y = node.y + y_offset; node.path_length = node.path_length+1; //Is this square on the board if((node.x &gt;= 0) &amp;&amp; (node.x &lt; 10) &amp;&amp; (node.y &gt;= 0) &amp;&amp; (node.y &lt; 10) &amp;&amp; //Is this square empty (board[node.x][node.y] == 0)) { workingset.push_back(node); board[node.x][node.y] = node.path_length; //Add to working set //Add to duplicates list } //(If a graphical animation is added, do it here, by printing the new board after each one, then sleeping for a few seconds) } </code></pre> <p>I get the runtime error 'list iterator not dereferencable'.</p> <p>I'm assuming this is to do with <code>workingset.pop_front()</code> being called from within the while loop, but I'm not sure what I should do to remedy this.</p> <p>Each loop, I want to get the node from the front of the list, work with it a little, then remove that node from the list. </p> <p>This is the code for generatelegalmove() - as you can see, if the new square is on the board (i.e. within the range of 0-9 in both dimensions of the array, and the square is empty) it will add this new node to the working set and the board[][] (which is effectively a duplicates list in effect) </p>
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    1. USEilidh
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      1. PO'list iterator not dereferencable'
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      1. VTUpMod
    1. COIt would be worth to add the declaration of the used variable workingset.
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      1. USharper
    2. COWhich particular line of the code you posted causes this error? Is it a compiler error or run-time error (debug check)?
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      1. PO'list iterator not dereferencable'
      1. USMaxim Egorushkin
    3. COWhat do you mean? It's added earlier in the program, it's a list of the struct square. I didn't add the entirety of my code because it's long and I assumed things such as using the include for a list, declaring the bool goal_found, initialising board[][] and workingset etc. would be assumed... Or do you mean something else??
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      1. USEilidh
 

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