Function error in c++ - c++

Question

I'm studying functions in c++ form a book called "jumping to c++" and there are a problem exercise that is create a calculator and I need make the arithmetic operation in separate functions, sound easy and I think I did it 90% good, the program gives me the correct answer but with some random numbers.
the code is:
#include <iostream>
using namespace std;
int a, b;
int sum()
{
return a + b;
}
int subs()
{
return a - b;
}
int div()
{
return a / b;
}
int mult()
{
return a * b;
}
int ask()
{
cout << "Give me the first number: ";
cin >> a;
cout << "\nGive me the second number: ";
cin >> b;
}
int main()
{
int opcion;
cout << "1. Sum \n2. Substraction \n3. Division \n4. Multiplication \n\nChoose one option from above: \n\n";
cin >> opcion;
if(opcion == 1)
{
cout << ask();
cout << "The result is: " <<sum() <<"\n\n";
} else if (opcion == 2)
{
cout << ask();
cout << "The result is: " << subs() <<"\n\n";
}else if (opcion == 3)
{
cout <<ask();
cout << "The result is: " << div() <<"\n\n";
}else if(opcion == 4)
{
cout << ask();
cout << "The result is: " << mult() <<"\n\n";
}else
{
cout << "Error.\n\n";
}
system("pause");
}
and this is the "error/bug/whatever"
1. Sum
2. Substraction
3. Division
4. Multiplication
Choose one option from above:
4
Give me the first number: 5
Give me the second number: 5
1878005856The result is: 25
Press any key to continue . . .
notice the error before of "The result is:"
appreciate any help, thanks

Answer 1

ask() does not return anything so it should be a void. Also, you do not need to do cout << ask(); since ask() already does the printing inside of it and it is a void (now) so it can't be printed.
Here is the code with the modifications, see comments with **** in front for changes:
#include <iostream>
using namespace std;
int a, b;
int sum() {
return a + b;
}
int subs() {
return a - b;
}
int div() {
return a / b;
}
int mult() {
return a * b;
}
void ask() { // **** Changed to void here
cout << "Give me the first number: ";
cin >> a;
cout << "\nGive me the second number: ";
cin >> b;
}
int main() {
int opcion;
cout << "1. Sum \n2. Substraction \n3. Division \n4. Multiplication \n\nChoose one option from above: \n\n";
cin >> opcion;
if (opcion == 1) {
ask(); // **** Removed cout <<
cout << "The result is: " << sum() << "\n\n";
} else if (opcion == 2) {
ask(); // **** Removed cout <<
cout << "The result is: " << subs() << "\n\n";
} else if (opcion == 3) {
ask(); // **** Removed cout <<
cout << "The result is: " << div() << "\n\n";
} else if (opcion == 4) {
ask(); // **** Removed cout <<
cout << "The result is: " << mult() << "\n\n";
} else {
cout << "Error.\n\n";
}
system("pause");
}
You can try it here
The random number was caused by you doing cout << ask(); even though you had not returned anything.
As aschepler pointed out "make sure you enable and read compiler warnings - there should be one saying that ask() doesn't return anything although declared to return an int."

Answer 2

The problem is your int ask() function.
It must return int value which you are writing to console with cout << ask();
The answer above won't work because you cannot write void to cout.
Since you do not return a value then a random number retruned. My compiler marks that as an error.
Replace type of ask function:
void ask()
{
cout << "Give me the first number: ";
cin >> a;
cout << "\nGive me the second number: ";
cin >> b;
}
Then replace cout << ask(); in every if statement with just ask();
Like this:
if (opcion == 1)
{
ask();
cout << "The result is: " << sum() << "\n\n";
}
else if (opcion == 2)
{
ask();
cout << "The result is: " << subs() << "\n\n";
}
else if (opcion == 3) ...
Consider checking if b==0 in case of devision operation. Or your program will crash if u try to devide by zero.

Answer 3

this function is returning a random integer. convert it to void
int ask()
{
cout << "Give me the first number: ";
cin >> a;
cout << "\nGive me the second number: ";
cin >> b;
}
new
void ask()
{
cout << "Give me the first number: ";
cin >> a;
cout << "\nGive me the second number: ";
cin >> b;
}