Jumping into C++ Ch 13 Problem 3 - Pointers

[bkushigian]

Hey all, I'm not sure what problem 3 of Jumping into C++ is asking me to do. For those of you who do not have the book, I'll reprint it here.

"Modify the program you wrote for exercise 1 so that instead of always prompting the user for a last name, it does so only if the caller passes in a NULL pointer for the last name."

The first exercise it refers to has us use pointers (or references) to have a function that changes the value of two strings (calling by reference I believe?). My code for the fist problem is as follows:

#include <iostream>#include <string>


using namespace std;


void names(string *p_first, string *p_last)
{
    cout << "What is your first name?:\n";
    cin >> *p_first;
    cout << "What is your last name?:\n";
    cin >> *p_last;
}


int main()
{
    string firstName, lastName;
    names(&firstName, &lastName);
    cout << firstName << " " << lastName;
    return 0;
}

So yea, just don't know what the question is asking. Does it just want me to add an

if (p_last == NULL)
{
//asks for last name etc.
}

in the names() function? Seems a bit trivial but maybe I'm over-thinking this

thanks

[rcgldr]

Your solution to this seems correct.

[Elkvis]

asking for a name only if the incoming pointer is NULL seems a bit nonsensical to me. if it's null, you can't dereference it. since you're passing with just a plain pointer to string, you can't return a string created by new through the parameter. the task seems pointless to me, and I don't understand what the author expects you to learn from it.

[rcgldr]

I missed the conflict with the problem statement in my previous post. I think the problem statement has this backwards. Perhaps the idea is to only ask for a first or last name if the corresponding pointer to string is not NULL, so that there is a place to store the response.

[vart]

I think this whole problem is backward - C style thinking way programming.

Function should receive a references not pointers and be overloaded to get only one parameter if user does not needs last name instead of relaying on C-style NULL pointer checking