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Logical error

Kovs95 (52)
Hi! Sorry im posting about this more! Iv'e worked on this some more and now when I debug it, it keeps repeating the "while" loop in the beginning: 

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while (grid[6][9] != player)
	{
		cout << "In which direction do you want to move?\n";
			cout << "up, down, left, right, or quit\n";
			cin >> imput;
			void showgrid();
	}

The strange thing is that it doesn't re-show the grid that I added at the end of the loop: void showgrid();.


After I type in "down", for example, it doesn't check if the move is valid, or move the player position. It just repeats 
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cout << "In which direction do you want to move?\n";
			cout << "up, down, left, right, or quit\n";
			cin >> imput;

It seems like the program is skipping over the rest of the code. It was working earlier! I'd appreciate anyone's comments
Thanks

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// Dungeon Crawler.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <string>

using namespace std;


int _tmain(int argc, _TCHAR* argv[])
{
	string imput;
	char player = 'G', trap = 'T', goal = 'X';
	char grid[7][10];
	int row, col, x = 0, y = 0;
	void showgrid();
	
	for(row = 0; row < 7; row++)// creates the grid 
	{
		for (col = 0; col < 10; col++)
		grid[row][col] = '.';
		
	}

	grid[x][y] = player; //Gives player's beginning position 
	grid[2][3] = trap; //Gives trap positions
	grid[3][6] = trap;
	grid[4][9] = trap;
	grid[5][4] = trap;
	grid[6][8] = trap;
	grid[6][9] = goal; //Gives finishing position
 
	void showgrid();
	{
		for (row = 0; row < 7; row++)  // Shows grid
		{
		for (col = 0; col < 10; col++)
			cout << grid[row][col];
			cout << "\n";
		
		}
	}

	while (grid[6][9] != player)
	{
		cout << "In which direction do you want to move?\n";
			cout << "up, down, left, right, or quit\n";
			cin >> imput;
			void showgrid();
	}

		if(imput != "up", "down", "left", "right", "quit")
		{
			cout << "That is not a valid imput. Please imput one of the following\n" 
				"up, down, left, right, or quit";
		}
			
		if(imput == "up")
		{
				if( y == 0 && x > -1 && x < 10)
				{
					cout << "You cannot move up from that position\n";
					cout << "In which direction do you want to move?\n";
					cout << "up, down, left, right, or quit\n";
					cin >> imput;
				}
				else
				{
					grid[x][y] = '.';
					grid[x][y--] = player; //re-locates player's position if move is valid
				}
		}

		
		if(imput == "down")
		{
				if(y == 6 && x > -1 && x < 10)
				{
					cout << "You cannot move down from that position\n";
					cout << "In which direction do you want to move?\n";
					cout << "up, down, left, right, or quit\n";
					cin >> imput;
				}
				else
				{
					grid[x][y] = '.';
					grid[x][y++] = player; //re-locates player's position if move is valid

				}
		}

		if(imput == "left")
		{
				if( y > -1 && y < 6 && x == 0)
				{
					cout << "You cannot move left from that position\n";
					cout << "In which direction do you want to move?\n";
					cout << "up, down, left, right, or quit\n";
					cin >> imput;
				}
				else
				{
					grid[x][y] = '.';
					grid[x--][y] = player; //re-locates player's position if move is valid
				}
		}

		if(imput == "right")
		{
				if( y > -1 && y < 10 && x == 9)
				{
					cout << "You cannot move right from that position\n";
					cout << "In which direction do you want to move?\n";
					cout << "up, down, left, right, or quit\n";
					cin >> imput;
				}
				else
				{
					grid[x][y] = '.';
					grid[x++][y] = player; //re-locates player's position if move is valid
				}
		}
		
		if(imput == "quit") //quits game if player chooses this command
		{
			return(0);
		}
		
		//the following is what happens if the player lands on one of the traps
		if(grid[2][3] == player || grid[3][6] == player || grid[4][9] == player || grid[5][4] == player || grid[6][8] == player) 
		{
			cout << "it's a trap!\n";
			return(0);
		}

		if(grid[6][9] == player) //What happens if player successfully makes it to the goal
		{
		cout << "You successfully escaped the dungeon!\n";
		}

		return(0);
	}
Chervil (7320)
 
 
    void showgrid();
is a declaration of the function prototype. This should go somewhere before the start of main()

If you actually want to call the function, do it like this:
 
 
    showgrid();


To define the function (outside of main() ) do something like this:
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void showgrid()
{
    // code for the function goes here
}


See Declaring functions here for an example: http://www.cplusplus.com/doc/tutorial/functions2/
Last edited on
Kovs95 (52)
When I define the function outside of the main function, it says the variables are undefined because they are all local variables. What do I do if they are local and the void is outside the main? Make then global variables?
Chervil (7320)
Making variables global can sometimes be done. But usually a better solution is to pass as parameters whichever variables the function requires.
vlad from moscow (6539)
Your original code is invalid. You think that below there is a function definition

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	void showgrid();
	{
		for (row = 0; row < 7; row++)  // Shows grid
		{
		for (col = 0; col < 10; col++)
			cout << grid[row][col];
			cout << "\n";
		
		}
	}


But you may not define a function inside another function. Why does not the compiler issue an error? Because it is not a function definition. At the end of the first line there is a semicolon:

void showgrid();

So the compiler considers the code as it consists from two parts: 1) function declaration

void showgrid();

and below the declaration some code block

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	{
		for (row = 0; row < 7; row++)  // Shows grid
		{
		for (col = 0; col < 10; col++)
			cout << grid[row][col];
			cout << "\n";
		
		}
	}


To correct the code you should 1) remove the semicolon 2) declare a function parameter.

So the valid code is

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	void showgrid( char grid[][10] )
	{
		for (row = 0; row < 7; row++)  // Shows grid
		{
		for (col = 0; col < 10; col++)
			cout << grid[row][col];
			cout << "\n";
		
		}
	}


This function definition you should place outside main.
In main or before main you should place its declaration

void showgrid( char grid[][10] );

Maybe there are other errors but I did not look through all your code because it is already enough that your code is invalid.





Last edited on
Kovs95 (52)
Ok, can you check if I passed the variables as parameters? I put the "void showgrid (parameters)" outside the main function and called on it as showgrid (parameters); inside of my functions. The variables are col, row, and grid[7][10]. Do I need to include the variables within the parentheses everytime I call on the function? Also, if I declared the variables, (int row, int col, char grid[7][10]), outside the main function, do I still have to declare them as local variables?
Thanks for all your help Chervil! cheers

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// Dungeon Crawler.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <string>

using namespace std;


void showgrid(int row, int col, char grid[7][10])
{
	for (row = 0; row < 7; row++)  // Shows grid
	{
		for (col = 0; col < 10; col++)
			cout << grid[row][col];
			cout << "\n";
		
	}
}

int _tmain(int argc, _TCHAR* argv[])
{
	string imput;
	char player = 'G', trap = 'T', goal = 'X';
	char grid[7][10];
	int x = 0, y = 0, row, col;
	

	for(row = 0; row < 7; row++)// creates the grid 
	{
		for (col = 0; col < 10; col++)
		grid[row][col] = '.';
		
	}

	grid[x][y] = player; //Gives player's beginning position 
	grid[2][3] = trap; //Gives trap positions
	grid[3][6] = trap;
	grid[4][9] = trap;
	grid[5][4] = trap;
	grid[6][8] = trap;
	grid[6][9] = goal; //Gives finishing position
 
	

	while (grid[6][9] != player)
	{
		cout << "In which direction do you want to move?\n";
			cout << "up, down, left, right, or quit\n";
			cin >> imput;
			showgrid(int row, int col, char grid[7][10]);
	}

		if(imput != "up", "down", "left", "right", "quit")
		{
			cout << "That is not a valid imput. Please imput one of the following\n" 
				"up, down, left, right, or quit";
		}
			
		if(imput == "up")
		{
				if( y == 0 && x > -1 && x < 10)
				{
					cout << "You cannot move up from that position\n";
					cout << "In which direction do you want to move?\n";
					cout << "up, down, left, right, or quit\n";
					cin >> imput;
				}
				else
				{
					grid[x][y] = '.';
					grid[x][y--] = player; //re-locates player's position if move is valid
				}
		}

		
		if(imput == "down")
		{
				if(y == 6 && x > -1 && x < 10)
				{
					cout << "You cannot move down from that position\n";
					cout << "In which direction do you want to move?\n";
					cout << "up, down, left, right, or quit\n";
					cin >> imput;
				}
				else
				{
					grid[x][y] = '.';
					grid[x][y++] = player; //re-locates player's position if move is valid

				}
		}

		if(imput == "left")
		{
				if( y > -1 && y < 6 && x == 0)
				{
					cout << "You cannot move left from that position\n";
					cout << "In which direction do you want to move?\n";
					cout << "up, down, left, right, or quit\n";
					cin >> imput;
				}
				else
				{
					grid[x][y] = '.';
					grid[x--][y] = player; //re-locates player's position if move is valid
				}
		}

		if(imput == "right")
		{
				if( y > -1 && y < 10 && x == 9)
				{
					cout << "You cannot move right from that position\n";
					cout << "In which direction do you want to move?\n";
					cout << "up, down, left, right, or quit\n";
					cin >> imput;
				}
				else
				{
					grid[x][y] = '.';
					grid[x++][y] = player; //re-locates player's position if move is valid
				}
		}
		
		if(imput == "quit") //quits game if player chooses this command
		{
			return(0);
		}
		
		//the following is what happens if the player lands on one of the traps
		if(grid[2][3] == player || grid[3][6] == player || grid[4][9] == player || grid[5][4] == player || grid[6][8] == player) 
		{
			cout << "it's a trap!\n";
			return(0);
		}

		if(grid[6][9] == player) //What happens if player successfully makes it to the goal
		{
		cout << "You successfully escaped the dungeon!\n";
		}

		return(0);
	}
vlad from moscow (6539)
The compiler shall issue an error. It is an invalid function call

showgrid(int row, int col, char grid[7][10]);

Instead of using arguments you declared parameters.
Also the function definition is invalid. Instead of

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void showgrid(int row, int col, char grid[7][10])
{
	for (row = 0; row < 7; row++)  // Shows grid
	{
		for (col = 0; col < 10; col++)
			cout << grid[row][col];
			cout << "\n";
		
	}
}


should be

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void showgrid(char grid[][10], int rows )
{
	for ( int i = 0; i < rows; i++ )	
	{
		for ( int j = 0; j < 10; j++ )  cout << grid[i][j] << ' ';
		cout << "\n";
	}
}
Last edited on
Kovs95 (52)
Ok thanks for all your imput Vlad! Your imput is very appreciated! Since i am new to c++, I am a little confused by your function definition.

First, you said, "Instead of using arguments you declared parameters." What do you mean by this? I thought I want to declare parameters in my def..

Second, why did you take out the 7 in char grid[][10]. Since the array is supposed to be a two demensional array of 7 by 10, I thought it's written as grid[7][10].

Lastly, I still receive an error that the "function does not take 0 arguments" I made your corrections. 

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while (grid[6][9] != player)
	{
		cout << "In which direction do you want to move?\n";
			cout << "up, down, left, right, or quit\n";
			cin >> imput;
			showgrid(char grid][][10], int rows);
	}


This part char grid appears red and it says "type name is not allowed". Do you know the problem to this?
vlad from moscow (6539)
One again it is not a function call

showgrid(char grid][][10], int rows);

Instead of passing arguments you declared parameters.

As for the declaration I showed then arrays passed by value implicitly are converted to a pointer to their first element. So all listed function declarations are equivalent and declare the same function

void showgrid(char ( *grid )[10], int rows );
void showgrid(char grid[][10], int rows );
void showgrid(char grid[7][10], int rows );
void showgrid(char grid[50000][10], int rows )
Last edited on
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