can someone check this? nightmare with functions

[slimeinstew]

this is the error:

build/Debug/Cygwin_4.x-Windows/main.o:main.cpp:(.rdata$.refptr.gameIsNotOver[.refptr.gameIsNotOver]+0x0): undefined reference to `gameIsNotOver'
build/Debug/Cygwin_4.x-Windows/main.o:main.cpp:(.rdata$.refptr.input[.refptr.input]+0x0): undefined reference to `input'

#include <iostream>
#include <vector>
#include <string>
#include <stdlib.h> /* exit(), EXIT_SUCCESS */
#include "main.h"
std::vector<std::string> board(9);
// Shows instructions to the player

void showInstructions() {
    std::cout << "Enter a number to place an X there. Get three in a row to win! /n";
    std::cout << "|1| |2| |3|/n";
    std::cout << "|4| |5| |6|/n";
    std::cout << "|7| |8| |9|/n";
    std::cout << "Press any key to continue! /n";
    std::cin.ignore();
}
// Shows the board

void showBoard(std::vector<std::string> board) {
    std::cout << "|";
    std::cout << board[0];
    std::cout << "| |";
    std::cout << board[1];
    std::cout << "| |";
    std::cout << board[2];
    std::cout << "|";
    std::cout << std::endl;
    std::cout << "|";
    std::cout << board[3];
    std::cout << "| |";
    std::cout << board[4];
    std::cout << "| |";
    std::cout << board[5];
    std::cout << "|";
    std::cout << std::endl;
    std::cout << "|";
    std::cout << board[6];
    std::cout << "| |";
    std::cout << board[7];
    std::cout << "| |";
    std::cout << board[8];
    std::cout << "|";
    std::cout << std::endl;
}
// Takes input from player

int playerInput() {
    int input;
    std::cout << "Input your move!";
    std::cin >> input;
    input - 1;
    return input;
}
// updates board after player moves

std::vector<std::string> updateBoard(int input, std::vector<std::string> &board) {
    if (input == 0) {
        if (board[0] == " ") {
            board[0] = "X";
        } else {
            std::cout << "Please input the number of a blank square.";
            playerInput();
        }
    }
    if (input == 1) {
        if (board[1] == " ") {
            board[1] = "X";
        } else {
            std::cout << "Please input the number of a blank square.";
            playerInput();
        }
    }
    if (input == 2) {
        if (board[2] == " ") {
            board[2] = "X";
        } else {
            std::cout << "Please input the number of a blank square.";
            playerInput();
        }
    }
    if (input == 3) {
        if (board[3] == " ") {
            board[3] = "X";
        } else {
            std::cout << "Please input the number of a blank square.";
            playerInput();
        }
    }
    if (input == 4) {
        if (board[4] == " ") {
            board[4] = "X";
        } else {
            std::cout << "Please input the number of a blank square.";
            playerInput();
        }
    }
    if (input == 5) {
        if (board[5] == " ") {
            board[5] = "X";
        } else {
            std::cout << "Please input the number of a blank square.";
            playerInput();
        }
    }
    if (input == 6) {
        if (board[6] == " ") {
            board[6] = "X";
        } else {
            std::cout << "Please input the number of a blank square.";
            playerInput();
        }
    }
    if (input == 7) {
        if (board[7] == " ") {
            board[7] = "X";
        } else {
            std::cout << "Please input the number of a blank square.";
            playerInput();
        }
    }
    if (input == 8) {
        if (board[8] == " ") {
            board[8] = "X";
        } else {
            std::cout << "Please input the number of a blank square.";
            playerInput();
        }
    }
    return board;
}

// If player wins

void playerWins() {
    char playerResponse;
    std::cout << "You win!";
    std::cin.get(playerResponse);
    if (playerResponse == 'y') {
        main();
    }
    if (playerResponse == 'n') {
        exit(EXIT_SUCCESS);
    } else {
        std::cout << "Please input your response again.";
        std::cin.get(playerResponse);
    }
}
// If player loses

void playerLoses() {
    char playerResponse;
    std::cout << "You lose!";
    std::cin.get(playerResponse);
    if (playerResponse == 'y') {
        main();
    }
    if (playerResponse == 'n') {
        exit(EXIT_SUCCESS);
    } else {
        std::cout << "Please input your response again.";
        std::cin.get(playerResponse);
    }
}
// If player ties

void playerTies() {
    char playerResponse;
    std::cout << "You tied!";
    std::cin.get(playerResponse);
    if (playerResponse == 'y') {
        main();
    }
    if (playerResponse == 'n') {
        exit(EXIT_SUCCESS);
    } else {
        std::cout << "Please input y/n.";
        std::cin.get(playerResponse);
    }
}

std::vector<std::string> computerMove(std::vector<std::string> &board) {
    if (board[0] == "" && board[1] == "X" && board[2] == "X") {
        board[0] = "O";
    } else if (board[0] == "X" && board[1] == "" && board[2] == "X") {
        board[1] = "O";
    } else if (board[0] == "X" && board[1] == "X" && board[2] == "") {
        board[2] = "O";
    } //etc
    return board;
}
//Checks if computer or player has won

bool checkForWinner(std::vector<std::string> board, bool gameIsNotOver) {
    if (board[0] == "X" && board[1] == "X" && board[2] == "X") {
        gameIsNotOver = false;
        return gameIsNotOver;
        playerWins();
    }
    if (board[0] == "O" && board[1] == "O" && board[2] == "O") {
        gameIsNotOver = false;
        return gameIsNotOver;
        playerLoses();
    }//etc
    // check for a tie
    int squares_filled = 0;
    for (int i = 0; i != 9; ++i) {
        if (board[i] != "") {
            ++squares_filled;
        }
    }
    if (squares_filled == 9) {
        playerTies();
    } else if (
            squares_filled != 9) {
        squares_filled = 0;
    } else {
        return gameIsNotOver;
    }
}

void gameLoop(bool gameIsNotOver) {
    int counter = 0;
    if (counter == 0) {
        showInstructions();
        ++counter;
    }
    while (gameIsNotOver == true) {
        showBoard(board);
        playerInput();
        updateBoard(input, board);
        checkForWinner(board, gameIsNotOver);
        computerMove(board);
        showBoard(board);
        checkForWinner(board, gameIsNotOver);
    }

}

int main() {
    gameLoop(gameIsNotOver);
    return 0;
}


// main.h

#ifndef MAIN_H
#define	MAIN_H
extern int input;
extern bool gameIsNotOver;
int main();
void showInstructions();
void showBoard(std::vector<std::string> board);
int playerInput();
std::vector<std::string> updateBoard(int input, std::vector<std::string> &board);
void playerWins();
void playerLoses();
void playerTies();
std::vector<std::string> computerMove(std::vector<std::string> &board);
bool checkForWinner(std::vector<std::string> board, bool gameIsNotOver);
void gameLoop(bool gameIsNotOver);
#endif 

[Zhuge]

In main.h, you have declared input and gameIsNotOver as extern, but you haven't actually defined them anywhere.

I think your problem is actually coming from not understanding functions. One things I see is on line 197 and 202, where you try to do something after having returned from the function. After you've returned, the function is finished; you cannot continue to do things after that point.

Additionally, checkForWinner() seems to be returning whether or not the game has ended yet, though on lines 231 and 234 you don't store the information or even try to use it.

[slimeinstew]

That is pretty true, i've been struggling with functions in this program alot and finding out I know alot less about them then I thought.

And thanks I totally missed that I didn't define either input or gameIsNotOver.

I'll define those variables and would putting the call to playerWins() or playerLoses() before the return fix that problem?

I'll take a look at how checkForWinner is working and I was planning on adding some conditionals and storing that somehow but I guess I just kinda blew right by that.
btw thanks a ton for such a nice reply.

[firedraco]

I'll define those variables and would putting the call to playerWins() or playerLoses() before the return fix that problem?

You would run those functions, and then execution would continue to the return statement and return the value, yes. If you don't know how to use a debugger, now would be a great time to learn as it will help you figure out how your code works.