4 replies to this topic

[camdaddy09]

hey guys, im just now jumping into c++ and i wrote a little something just goofing around and testing out all the stuff ive learned so far. in the program below ive found a bug when option one is selected and the user types in more than his first name, like firstname space lastname. the string is supposed accept any character including spaces up to the specified amount of characters, but if you copy paste, compile and run it this does not happen. I cant figure out where this bug is coming from and i dont know how to use xcode to debug so im looking for some experienced help on this one.

#include <iostream>
#include <math.h>


void printName();
void squareRoot();
void clearScreen();

int main ()
{
    using namespace std;
    
    int choice = 0;
    char exitChoice = '\0';
    
    
    clearScreen();
    do 
    {
        
        cout << "Type in a number that corresponds to one of the options below";
        cout << "\nthen hit 'enter' or 'return'.";
        cout << "\n\t\t\t****MENU****";
        cout << "\n\t\t\t(1) First name";
        cout << "\n\t\t\t(2) Find sqaure root";
        cout << "\n\t\t\t(3) option 3";
        cout << "\n\t\t\t(4) exit";
        cout << "\n";
        cin >> choice;
        switch (choice)
        {
            case 1:
                clearScreen();
                printName();
                break;
            case 2:
                clearScreen();
                squareRoot();
                break;
            case 3:
                clearScreen();
                cout << "You picked option three!\n\n";
                break;
            case 4:
                exitChoice = 'y';
                break;
            default:
                clearScreen();
                cout << "~~~~~~~~~~~~ PICK AGAIN! ~~~~~~~~~~\n\n";
            
        }//                                                end switch
        
    }//                                                    end loop
    while (exitChoice != 'y');
    
    
    return 0;
}

void printName()
{
    using namespace std;
    
    char buffer[80] = {'\0'};
    cout << "Enter your name ";
    cin >> buffer;
    cout << "Hey " << buffer << "!\n\n";     
    return;
}


void squareRoot()
{
    double a = 0;
    std::cout << "enter a number: ";
    std::cin >> a;
    a = sqrt(a);
    std::cout << "The square root is " << a << "\n\n";
    return;
}

void clearScreen()
{
    for (int i = 0; i < 100; i++)
    {
        std::cout << "\n\n\n\n\n";
    }
    
    return;
}

[Alexander]

Your issue is that cin is formatted input, it will break at the first name and continue. If you want a first and last name, you will have to use something such as cin.getline() for this and separate them afterwards if required, or just list the full name as accepted.

Further, since the string format is not entirely relevant to your issue you may as well turn it in to an std::string object - cstrings are cumbersome. You will have to use getline instead of cin.getline if you were to switch to std::string however

Try to start there and report back, the cin.getline documentation is here: istream::getline - C++ Reference
getline() getline - C++ Reference

[camdaddy09]

well alexnder i used cin.get() and i dont know if this is the same thing but it didnt work when i used it.
heres the amended function

void printName()
{
    using namespace std;
    
    char  buffer[80]={'\0'} ;
    
    cout << "Enter your first name: ";
    cin.get(buffer,79);
    
    clearScreen();
    cout << "Hey " << buffer << "!\n\n";     
    return;
}

[Alexander]

A pseudo-interaction with your program would look like this:

Prompt: Enter choice: (you enter 1 and hit <enter>)
Buffer: 1 is removed due to the formatted cin input, newline from enter still remains
Prompt: Enter name: (newline goes here automatically, is  whitespace, is ignored, continues in possibly infinite loop)

Personally I would accept choice as a string (getline()), and compare it as a string. If someone does not enter a proper integer (as choice is an integer) it can also go in to an infinite loop. You should maybe employ some error checking (there're facilities for that with std::cin, however that is not my forté).

[camdaddy09]

how do i test to make sure

choice

is an int?
or better yet how do i make absolute sure that the newline character goes away after hitting enter?