Dynamic String Arrays, compile errors

Question

I've been working on this assignment for class for about a month now. It's way past due and I'm trying to finish it more for my own benefit so I understand how dynamic arrays and pointers work. I'm still quite new to C++ and would appreciate any information you can provide. I thank you for your time ahead of time.

Take note id, cstation, lab are other variables used in other parts of the program to create a menu, search and login functions and are working properly.

The error I'm getting with my code is:

project_9_5.cpp: In function ‘void arraysize(std::string&, int&, int&, std::string***, std::string*)’:
project_9_5.cpp:79:22: error: expected primary-expression before ‘[’ token
   { labs[i] = string [labsize[i]]; }
                      ^
project_9_5.cpp:81:46: error: expected primary-expression before ‘]’ token
  fillarrays(id, cstation, lab, labs, labsize[]);

My Code:

const string LAB1 = "5";
const string LAB2 = "6";
const string LAB3 = "4";
const string LAB4 = "3";

void arraysize(string &id, int &lab, int &cstation, string **labs[], string labsize[]);
void fillarrays(string &id, int &lab, int &cstation, string **labs[], string labsize[]);
void printarrays(string &id, int &cstation, int &lab, string **labs[], string labsize[]);
void removearrays(string **labs[]);

int main() {
    string **labs[TOTAL_LABS];
    string labsize[TOTAL_LABS] = { LAB1,LAB2,LAB3,LAB4 };

    arraysize(id, cstation, lab, labs, labsize);
    printarrays(id, cstation, lab, labs, labsize);
    removearrays(labs);
return 0;
}

void removearrays(string **labs[]) {

    delete [] labs;
}

void arraysize(string &id, int &lab, int &cstation, string **labs[], string labsize[]) {  //TOnnings example

    //int labsize[TOTAL_LABS] = { LAB1,LAB2,LAB3,LAB4 };

    labs = new string **[TOTAL_LABS];

    for(int i=0; i< TOTAL_LABS; i++)
        { labs[i] = string [labsize[i]]; }

    fillarrays(id, cstation, lab, labs, labsize[]);
}


void fillarrays(string &id, int &lab, int &cstation, string **labs[], string labsize[]) {

    for(int row = 0; row<TOTAL_LABS;row ++) {
        for(int col=0; col<TOTAL_LABS; col++) {
            **labs[row] = "Empty";
        }
    }   
}

void printarrays(string &id, int &cstation, int &lab, string **labs[], string labsize[]) {

    cout << "\nLabs#" << "  " << "Computer Stations" << endl;;
    for(int rows=0 ;rows<TOTAL_LABS; rows++) {
        cout << " " << (rows+1) << ":    ";
        for(int cols=0; cols<TOTAL_LABS; cols++) {
            cout << (cols+1) << ": ";
            cout << labs[rows] << "     ";
        }   
    cout << endl;
    }
    //menu(id, cstation, lab, labs);
}

All these pointers annoy me and surely any other reader. Pointers in C++ are mostly unnecessary and try to avoid them! And remember that C++ passes everything non-reference by value, so labs = new string **[TOTAL_LABS]; will assign to the argument. — cadaniluk
– cadaniluk, Commented Dec 5, 2015 at 20:35
I agree, I would be using vectors or some other type if I could, The assignment was specifically on pointers and dynamic arrays however, so can't be avoided :/ — M Hernandez
– M Hernandez, Commented Dec 5, 2015 at 21:13

Evgeniy331 · Accepted Answer · 2015-12-05 20:43:49Z

1

Declaration of function:

void arraysize(string &id, int &lab, int &cstation, string **labs[], string labsize[]);

You call this function:

arraysize(id, cstation, lab, labs, labsize);

cstation and lab not on their position .printarrays and fillarrays the same problem

I don't know what you want to do on this line

{ labs[i] = string [labsize[i]]; }

But you can not use type name like array

On this line, [] with labsize not neccessary.

fillarrays(id, cstation, lab, labs, labsize[]);

And removearrays need to changes:

void removearrays(string **labs[]) {
for (int i = 0; i < TOTAL_LABS; i++)
       delete [] labs[i];
delete [] labs;
}

answered Dec 5, 2015 at 20:43

Evgeniy331

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1 Comment

M Hernandez Over a year ago

This totally makes sense to me. THANK YOU. It would explain why I was getting Seg faults when I was messing with it.

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