Getline and for Loops

[wade34fly]

here is the code i been playing around with

using namespace std;
const int COLS = 5;
void initializeArray( int [][COLS], int);
 
int main(int argc, char *argv[])
{
    const int ROWS = 3;
 
 
 
 
 
    int scores [ROWS][COLS];
    string names[ROWS];
    initializeArray(scores, ROWS);
 
    for (int i = 0; i < ROWS; i++)
    {
        names[i] = "";
    }
 
 
    for (int i = 0; i < ROWS; i++)
    {
        for (int j = 0; j < COLS; j++)
        {
            cout << scores[i][j] << " ";
        }
        cout << endl;
 
    }
    cout << endl;
    // fill the array
    for (int i = 0; i < ROWS; i++)
    { 
        cout << "Name: " << names[i];
        getline(cin,names[i]);
        cout << "Please enter " << names[i] << " scores: ";
 
        for (int j = 0; j < COLS; j++)
        {
                cin >> scores[i][j];
 
        }   
 
    }
    //print
    for (int i = 0; i < ROWS; i++)
    {
        cout << names[i] << " : ";
        for (int j = 0; j < COLS; j++)
        {
            cout << scores[i][j] << " ";
        }
        cout << endl;
 
    }
    cout << endl;
 
    system("PAUSE");
    return EXIT_SUCCESS;
}
void initializeArray( int in[][COLS], int size)
{
    for (int i = 0; i < size; i++)
    {
        for (int j = 0; j < COLS; j++)
        {
            in[i][j] = 0;
        }
    }
}

its a program that you enter a students name then you enter scores in array. i cant seem to find out why it wont let me enter the 2nd name?? the scores work fine. Can anybody help??? thanks

[Ganon11]

This is a problem with C++, so I'll move it to the C++ / C Forum.

[Ganon11]

There are 2 things I see wrong with this code:

1) You're outputting the contents of scores before you give them any values, so this is going to clutter up your output screen with garbage values.

2) You're using a mixture of getline and cin >> statements, which always leads to the following problem:

When cin is inputting normally (i.e. cin >> scores[i]), it looks for some characters surrounded by whitespace. When it finds this, it inputs the characters, gets rid of the first whitespace, and leaves the last whitespace character there. So, after you input all the scores, there is a newline character ('\n') still there.

When getline is inputting, it looks for any number of characters (including 0) before a newline character ('\n') and returns those characters - it then eats the newline character (so that another getline call will work as expected).

In your situation, you cin >> several times, and when you're done, there is a '\n' still in the input stream. When getline is called, it finds that newline character, thinks, "Cool, I'm done." and returns what characters it found - which is none!

In order to fix this, you need to get rid of that newline character - either by calling cin.get() with a garbage character variable, or with a call to cin.ignore().

EDIT: Oh, I just saw your initializeArray method. So the scores array will have all 0s. Still, I see no reason to print there (except to check that your function worked correctly).

[wade34fly]

There are 2 things I see wrong with this code:

1) You're outputting the contents of scores before you give them any values, so this is going to clutter up your output screen with garbage values.

2) You're using a mixture of getline and cin >> statements, which always leads to the following problem:

When cin is inputting normally (i.e. cin >> scores[i]), it looks for some characters surrounded by whitespace. When it finds this, it inputs the characters, gets rid of the first whitespace, and leaves the last whitespace character there. So, after you input all the scores, there is a newline character ('\n') still there.

When getline is inputting, it looks for any number of characters (including 0) before a newline character ('\n') and returns those characters - it then eats the newline character (so that another getline call will work as expected).

In your situation, you cin >> several times, and when you're done, there is a '\n' still in the input stream. When getline is called, it finds that newline character, thinks, "Cool, I'm done." and returns what characters it found - which is none!

In order to fix this, you need to get rid of that newline character - either by calling cin.get() with a garbage character variable, or with a call to cin.ignore().

EDIT: Oh, I just saw your initializeArray method. So the scores array will have all 0s. Still, I see no reason to print there (except to check that your function worked correctly).

yea i had the 0 to check if it works but i know its works withthe scores. but what im having problems with is the name.


I ask user to enter name: (user enters "john bert")
Then i ask enter scores(5): (user enters "12 23 34 45 56")
I want to aske for second name but it wont let me it skips the name and goes right into scores again. so i put scors again.


Im supose to have 3 names and 3 rows of scores:

Looks like this:

John bert: 12 23 34 45 56
:32 43 54 65 77
:44 45 56 67 86

when it should be:

John bert: 12 23 34 45 56
jones smith:32 43 54 65 77
robert jon :44 45 56 67 86

[oler1s]

Reread Ganon's reply. He explains why inputting the name is skipped over.

When you use cin, you don't clear the entire stream buffer. There's a newline left over because it's clearly not a number. Unfortunately, when you use getline, it picks up on this stray newline and returns. So you do get a name. It's '\n'. Not what you want.

The solution is to either use getline consistently. For the numbers, use getline to grab all the numbers in one go, and then use a stringstream to parse out each number individually.

The other option is to dump the contents of the buffer after using cin. cin.ignore or cin.sync (I think) will do the trick.

[wade34fly]

Reread Ganon's reply. He explains why inputting the name is skipped over.

When you use cin, you don't clear the entire stream buffer. There's a newline left over because it's clearly not a number. Unfortunately, when you use getline, it picks up on this stray newline and returns. So you do get a name. It's '\n'. Not what you want.

The solution is to either use getline consistently. For the numbers, use getline to grab all the numbers in one go, and then use a stringstream to parse out each number individually.

The other option is to dump the contents of the buffer after using cin. cin.ignore or cin.sync (I think) will do the trick.

oh damn im sorry i totally skipped that whole paragraph he wrote dont know how that happened lol thanks both of u

[wade34fly]

ok i fixed the skipping the the name part witht he getline ignore. but now i cant figureout y int he first name i enter it cuts off the first letter?

when i run it i get this

eter smith: 1 2 3 4 5
peter smith: 1 2 3 4 5
peter smith: 1 2 3 4 5

when it should be
peter smith: 1 2 3 4 5
peter smith: 1 2 3 4 5
peter smith: 1 2 3 4 5

it only appears how it suppose to when i enter it like this.

It askes me Name: (I enter) (spacebar )Peter smith

how do i fix it so that it works when i just enter it and dont need to press spacebar? Sorry im new with c++ and trying to get a hold of this.

[Ganon11]

I'm assuming you are using cin.get() as suggested? Put it directly after the cin >> statements, rather than before the getline statement.

[wade34fly]

I'm assuming you are using cin.get() as suggested? Put it directly after the cin >> statements, rather than before the getline statement.

great thanks.. you the man! now i gotta get to creating functions lol this should be fun. thanks for the help guys