Load functions using a case switch statement

Question

I'm writing a program in C++ and I've been able to get it to compile and start to run how ever when I choose an option the coresponding function that is supposed to be called by a switch-case statement isn't called. Am I missing something in my code?

//The following program framework is given.
//Add the programming logic to complete the assignment.
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
using namespace std;
//function prototypes should be placed here
//Main must be the first function in the program. Write other functions after it.
int main()
{
char cInput;
string strFileName;
vector<string> vecStudent;
cout<<"Please enter the data file name (with location): ";
cin >> strFileName;
//call a function to read the content of the input file into
//the vector vecStudent
while (true)
{
cout<<"----------------------------------------"<<endl;
cout<<" Student Record - Main Menu "<<endl;
cout<<"----------------------------------------"<<endl;
cout<<" Enter 1 to display ALL students"<<endl;
cout<<" Enter 2 to add a student name"<<endl;
cout<<" Enter 3 to delete a student name"<<endl;
cout<<" Enter 4 to SAVE and quit the program"<<endl;
cout<<"----------------------------------------"<<endl;
cout<<"Enter menu option: ";
cin>>cInput;
switch (cInput)
{
case '1':
//call function display names
   void displaynames();
break;
case '2':
   void addname();
//call a function add name
break;
case '3':
    void deletename();
//call function delete names
break;
case '4':
   void  saveandquit();
//call function save and quit
return 0;

if( cInput != 1,2,3,4)
cout<<"invalid input"<<endl;
break;
}
}
return 0;
}

int displaynames()
{
    ifstream inFile;
    ofstream outFile;
    string strFileName;
    string strFName,strLName;
    vector<string> vecStudent;
    char line[80];

    // open input file
    inFile.open(strFileName.c_str());
    if (inFile.fail())
    {
        cout << " Input file error!" << endl;
            return -1;
    }
    while (inFile>>strFName>>strLName)
        vecStudent.push_back(strFName+ " "+strLName);
    inFile.close();

    //display the content of the vector
    for(int i =0; i< vecStudent.size();i++)
        cout<<vecStudent[i]<<endl;
return 0;
}

int addname()
{
    ifstream inFile;
    ofstream outFile;
    string strFileName;
    string strFName,strLName;
    vector<string> vecStudent;
    char line[80];
    //add a new name
    cout << endl<< " Enter a new name( First and Last Name):";
    cin>>strFName>>strLName;
    vecStudent.push_back(strFName+ " "+strLName);

    // open output file for writing
    outFile.open(strFileName.c_str());
    if ( outFile.fail())
    {
        cout<<" Output file error! Student was not added"<<endl;
        return -1;
    }

    //display the content of the vector
    for(int i=0; i<vecStudent.size(); i++)
        cout<< vecStudent[i]<<endl;

    for(int i=0; i<vecStudent.size();i++)
        outFile<<vecStudent[i]<<endl;
    outFile.close();
return 0;
}


int saveandquit()
{
    ifstream inFile;
    ofstream outFile;
    string strFileName;
    string strFName,strLName;
    vector<string> vecStudent;
    int i=0;
    char line[80];
    //     open output file for writing
    outFile.open(strFileName.c_str());
    if ( outFile.fail())
    {
        cout<<" Output file error!"<<endl;
        return -1;
    }

    //display the content of the vector
    for(int i=0; i<vecStudent.size(); i++)
        cout<< vecStudent[i]<<endl;

    for(int i=0; i<vecStudent.size();i++)
        outFile<<vecStudent[i]<<endl;
    outFile.close();
    cout << " file saved. enter -1 to quit";
    cin>> i;
    if( i=-1)


    return 0;
}



 int deletename()
{
    ifstream inFile;
    ofstream outFile;
    string strFileName;
    string strFName,strLName;
    vector<string> vecStudent;
    int namepos = 0;
    char line[80];

    inFile.open(strFileName.c_str());
    if (inFile.fail())
        cout <<"Input file error!"<<endl;

    //read the names from the file into the vector
    while (inFile >> strFName >> strLName)
        vecStudent.push_back(strFName+" "+strLName);
    inFile.close();

    cout <<"\nEnter the name to be deleted (First name and Last name): ";
    cin >>strFName >>strLName;

    int i=0, pos=-1;
    int size = vecStudent.size();
    bool found=false;
    // use a linear search to find the name in the vecotor of names

    while (i < size && !found)
    {
        if (vecStudent [i] == strFName+" "+strLName)
        {
            found = true;

    cout <<"\nthat name is in the "<<(pos + 1) <<" position in the list\n";
    cout <<"Please enter the position in list\n";
    cin>> pos;
    // use an iterator to delete name from vecStudent. vector.erase requires an iterator. used a while loop to find the name and make sure it was in the
    // vector of strings. then the loop displays the position in the vector that the string is. the program asks the user to enter the number position of the name
    // from there the user enters the name and the program uses a for loop to find the position and the built in vector.erase to remove the name from the list.
    for(int i=0; i ==pos; i++)
    {
        if(i == pos)
        {
            vecStudent.erase (vecStudent.begin());
        }
    }
    }
    }

    return 0;
}

Solution 1

You are actually just declaring functions instead of calling them.

void displaynames();

Declares a function.

displaynames();

Calls a function.

Solution 2

You are calling the functions wrong. It should be

case '1':
//call function display names
   displaynames();
break;
case '2':
   addname();
//call a function add name
break;
case '3':
    deletename();
//call function delete names
break;
case '4':
   saveandquit();

To call a function, you just need the function name and the function parameters (which in this case, seem to be none. The way you currently have it is declaring a function rather than calling a function.

Solution 3

In your code block (switch), you're not calling any functions, but rather just declaring them.

...
case '1':
//call function display names
   void displaynames();
break;
...

Move the (forward) declarations (void displaynames();) to the top level of your source file (as you're defining the functions after using them), and then call them using the normal function application syntax (displaynames();).

From somewhere on the net:

"A declaration for a function is also called a prototype and it informs the compiler of your intent to define and to use it. A definition for a function is the body (code) associated with the prototype."

Comments

[Amardeep AC9MF]

Further, the syntax originally used is called a function declaration and will need to come before the functions are actually called since the function definitions come after the main() where they are used.

[josephthomas]

@Amardeep: He mentions in his code comments that the declarations are above main, he seems to just be confused on how to call the functions.

[Amardeep AC9MF]

Those comments look like boilerplate. I'm sure if he knew what a prototype was he would not have made the mistake he did.

[user1319815]

where do I need to declare the function? I tried declaring them before the main and it wouldn't compile.

[Alok Save]

@user1319815: Declare them before the main() and call them inside your switch-case.