Extending my array - c++

Question

From what I am reading from the book and from prior examples that I have been doing from the book this is what I have come up with. I appreciate the extra advice but I am trying to learn what the chapter is trying to show me so I can move on and learn the basics before I try code I have never seen before. I want the user to type 0 to end the loop but for some reason the loop keeps going? I think I may be missing something that is preventing it from stopping.
// Ex4_08.cpp
// Initializing pointers with strings
#include <iostream>
using std::cin;
using std::cout;
using std::endl;
int main()
{
bool keepgoing = true;
int answer;
while (keepgoing = true)
{
const char* pstr[]{ "Aa", // Initializing a pointer array
"Bb",
"Cc",
"Dd",
"Ee",
"Ff",
"Gg",
"Hh",
"Ii",
"Jj",
"Kk",
"Ll",
"Mm",
"Oo",
"Pp",
"Qq",
"Rr",
"Ss",
"Tt",
"Uu",
"Vv",
"Ww",
"Ss",
"Yy",
"Zz",
};
const char* pstart{ "Your letter is " };
int dice{};
cout << endl
<< "Enter a number between 1 and 26 " << _countof(pstr) << ": ";
cin >> dice;
cout << endl;
if (dice >= 1 && dice <= _countof(pstr)) // Check input validity
cout << pstart << pstr[dice - 1]; // Output star name
else
cout << "Sorry, you haven't selected a correct number."; // Invalid input
cout << "Do you want to do this again? Type 0 for no: " << endl;
cin >> answer;
if (answer == 0)
{
keepgoing = false;
}
}
cout << endl;
return 0;
}

Answer 1

I've modified you initial code sample, using vector and string which are more C++ and easier to use:
#include <iostream>
#include <string> // for string
#include <vector> // for vector
using std::cin;
using std::cout;
using std::endl;
int main()
{
std::vector<std::string> pstr;
for (char c = 'a'; c <= 'z'; c++) // cycle over the 26 ASCII letters
{
std::string temp; //
temp += c - 32; // add capital character (e.g A)
temp += c; // add character (e.g. a)
pstr.push_back(temp); // push the new string (e.g. Aa) to the vector
}
const char* pstart{ "Your letter is " };
int dice{};
while (true)
{
cout << endl
<< "Enter a number between 1 and 26 " << pstr.size() << ": ";
cin >> dice;
if (dice == 0)
{
break; //break if the user enters 0
}
cout << endl;
if (dice >= 1 && dice <= pstr.size()) // Check input validity
cout << pstart << pstr[dice - 1]; // Output star name
else
cout << "Sorry, you haven't selected a correct number."; // Invalid input
}
cout << endl;
return 0;
}

Answer 2

Your code is wrong here:
while (keepgoing = true) {
...
if (answer == 0) {
keepgoing = false;
}
}
You are setting the keepgoing to false, but in the while condition you are resenting it to true. You must use the == operator (as in while(keepgoing == true)) or remove it (while(keepgoing)).
Otherwise, you may use while(true) or for (;;) and break instead of keepgoing = false:
for (;;) { // or while (true); to me, that's only a matter of preference.
...
if (answer == 0) {
break; // exit the loop
}
}
They do produce infinite loop until you enter the break condition.

Answer 3

Change this line:
while (keepgoing = true)
To this:
while (keepgoing == true)
The first assigns the value true to the variable keepgoing. The second checks of the value of keepgoing is true. This is a very common issue that trips of many new programmers (and occasionally an old one). :-)