Undefined reference when attempting to pass 2d array as parameter

Question

I am having trouble figuring out how to pass a 2d array as a parameter. The C++ manual and other examples i'm finding aren't helping me much so maybe someone can help me understand more if they take a look at my code. Thanks

header:

#ifndef HEADER_H_INCLUDED
#define HEADER_H_INCLUDED


#include <iostream>
#include <iomanip>
#include <fstream>
#include <cctype>
#include <cstdlib>
#include <string>

using namespace std;

void extern readFile(ifstream&, int&, int&, int&, int&, int[][6]);
void extern userInput(int&, int&, int&, int&, int&, int&, char&, char&, int[][6]);
void extern findSeats(int&, int&, int&, int&, int&, int&, char&, char&, int[][6]);

#endif // HEADER_H_INCLUDED

main

#include "header.h"

int main()

{
    ifstream inFile;
    int FC_Row, FC_Col, EconRow, EconCol, ticketNum, rowNum;
    int airplane[100][6];
    char ticketType, seatType;

    cout << setw(48) << "Thank you for choosing Cheeta Airlines!" << '\n' << '\n' << endl;
    ifstream inData;

    inData.open("Airplane.txt");

    if (!inData)
    {
        cout << "Cannot open the input file."
             << endl;
            return 1;
    }

    readFile(inFile, FC_Row, FC_Col, EconRow, EconCol, airplane[100][6]);
userInput(FC_Row, FC_Col, EconRow, EconCol, ticketNum, rowNum, ticketType, seatType,     airplane[100][6]);`

}

readFile:

#include "header.h"

void readFile(ifstream& inFile, int& FC_Row, int& FC_Col, int& EconRow, int& EconCol, int airplane[][6])
{
    int a, b;

    inFile.open("Airplane.txt");

    inFile >> FC_Row >> FC_Col >> EconRow >> EconCol;

    for (a = 0; a < FC_Row; a++)
    for (b = 0; b < FC_Col; b++)
        inFile >> airplane[a][b] ;

    for (a = 0; a < EconRow; a++)
    for (b = 0; b < EconCol; b++)
        inFile >> airplane[a + FC_Row][b] ;

    cout << setw(11)<< "A" << setw(6) << "B"
    << setw(6) << "C" << setw(6) << "D"
    << setw(6) << "E" << setw(6) << "F" << endl;
    cout << " " << endl;

    cout << setw(30) << "First Class: $2,000" << endl;
    cout << '\n';
    for (a = 0; a < FC_Row; a++)
    {
        cout << "Row " << setw(2) << a + 1 << ":";
        for (b = 0; b < FC_Col; b++)
        cout << setw(5) << airplane[a][b] << " ";

        cout << endl;
    }

    cout << '\n';
    cout << setw(30) << "Economy Class: $750" << endl;
    cout << '\n';
    for (a = FC_Row; a < (EconRow + FC_Row); a++)
    {
        cout <<"Row " << setw(2)<< a + 1 << ":";
        for (b = 0; b < EconCol; b++)
        cout << setw(5) << airplane[a][b] << " ";

        cout << endl;
    }


}

Mahesh · Accepted Answer · 2011-03-12 23:20:36Z

3

If you need to pass a 2D array -

void extern readFile(ifstream&, int&, int&, int&, int&, int[][6]);

void readFile(ifstream&, int&, int&, int&, int&, int[][6])
{
     // ....

}

And the call should be -

readFile(inFile, FC_Row, FC_Col, EconRow, EconCol, airplane);

When you say -

readFile(inFile, FC_Row, FC_Col, EconRow, EconCol, airplane[100][6]);

You are actually passing the value at that position ( i.e., int ). But the function expects a int [][6].

answered Mar 12, 2011 at 23:20

Mahesh

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11 Comments

darko Over a year ago

mashesh, thanks for the answer. After these changes I am getting an error telling me that airplane is undeclared in my readfile function.

Mahesh Over a year ago

@Matt - Keeping the error aside, why are you using extern in this case. Any reason ?

darko Over a year ago

Extern is used because all functions are located in different .cpp file. the program runs after I redeclare int airplane[100][6] in each function.

Matheus Moreira Over a year ago

You can omit variable identifiers from prototype declarations, but not from the implementation signature.

Mahesh Over a year ago

@Matt - 0k. Will narrow down the mistake. In the beginning of reading loop - for (a = 0; a < FC_Row; a++){ for (b = 0; b < FC_Col; b++){ inFile >> airplane[a][b] ; std::cout << airplane[a][b] << "\t";}} ..Check this whether it is correctly reading or not .

|

Matheus Moreira · Accepted Answer · 2011-03-12 23:25:05Z

1

The last parameter is declared as an int, but a 2D int array is of type int[][depth].

Change the readFile prototype declaration to:

void extern readFile(ifstream&, int&, int&, int&, int&, int[][6]);

Later, when you call the function, you are passing the element inside the array, which is of type int:

readFile(inFile, FC_Row, FC_Col, EconRow, EconCol, airplane[100][6]);

The function is expecting a 2D int array, which is of type int[][6], so you must pass only the variable itself, without any indexes:

readFile(inFile, FC_Row, FC_Col, EconRow, EconCol, airplane);

edited Mar 12, 2011 at 23:25

answered Mar 12, 2011 at 23:11

Matheus Moreira

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3 Comments

darko Over a year ago

"cannot convert int*' to int (*)[6]"

Matheus Moreira Over a year ago

Are you outputting the contents of the array (cout << array[i][j];), or the array itself (cout << array;)?

darko Over a year ago

I am outputting array[i][j] in a loop. See the readFile function where it is initially filled and output. In the different function it is the exact code being used.

Community · Accepted Answer · 2017-05-23 12:26:50Z

0

These might lead you to the proper solution

Passing multidimensional arrays as function arguments in C

http://c-faq.com/aryptr/ary2dfunc2.html

edited May 23, 2017 at 12:26

CommunityBot

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answered Mar 12, 2011 at 23:31

celavek

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