Moving For Loop to Function - c++

Question

in the following code I have a for loop in my main function. Since a function can't return 2 values, what are some ways I could create a function, or functions, to remove it from my main function. Thanks!
#include <iostream>
#include <cmath>
using namespace std;
int getNumberExercises();
int getScores(int numberOfExercises);
int getPoints(int numberOfExercises);
double roundToTenth(double number);
double calcPercentage(int totalScore, int totalPoints);
void getTotal(int totalScore, int totalPoints, double scorePercentage);
int main() {
int numberOfExercises = 0;
int totalScore = 0;
int totalPoints = 0;
double scorePercentage = 0.0;
numberOfExercises = getNumberExercises();
for (int i = 1; i <= numberOfExercises; i++) {
totalScore += getScores(i);
totalPoints += getPoints(i);
}
scorePercentage = calcPercentage(totalScore, totalPoints);
getTotal(totalScore, totalPoints, scorePercentage);
return 0;
}
int getNumberExercises() {
int numberOfExercises;
cout << "How many exercises to input? ";
cin >> numberOfExercises;
cout << endl;
return numberOfExercises;
}
int getScores(int i) {
int score = 0;
cout << "Score received for exercise " << i << ": ";
cin >> score;
return score;
}
int getPoints(int i) {
int points = 0;
cout << "Total points possible for exercise " << i << ": ";
cin >> points;
cout << endl;
return points;
}
double roundToTenth(double number) {
return floor(number * 100 + 0.5) / 100;
}
double calcPercentage(int totalScore, int totalPoints) {
double scorePercentage = (double) totalScore / totalPoints * 100;
return scorePercentage;
}
void getTotal(int totalScore, int totalPoints, double scorePercentage) {
cout << "Your total is " << totalScore << " out of " << totalPoints << ", or " << roundToTenth(scorePercentage) << "%";
}

Answer 1

Either typedef a std::pair to a descriptive name, or create your own type to hold the things you want to return:
using ScorePointPair = std::pair<int, int>; // C++11
typedef std::pair<int, int> ScorePointPair; // pre C++11
Or
struct ScorePointPair
{
int score;
int points;
};
Then simply return this from your function (by value):
ScorePointPair fun()
{
// Loop etc...
return {score, points};
};
I would recommend the custom type (struct/class) approach, as this tends to be more maintainable.

Answer 2

To return multiple values use pass by pointer:
void modify(int *val1, int *val2)
{
*val1 = 46;
*val2 = 100;
}
In caller:
int a, b;
modify(&a, &b);
Now a will be 46, and b will be 100. This is because the address is copied, rather than the actual variable, which is what happens in pass by value.
So if you want to find the number of occurences of tabs and commas in a file:
void findtabcomma(const char *fn, int *ncomma, int *ntab)
{
FILE *fp;
int c;
if (fp = fopen(fn, "r")) {
while ((c = getc(fp)) != EOF) {
if (c == '\t')
++(*ntab);
if (c == ',')
++(*ncomma);
}
fclose(fp);
}
}
You can use the function like this:
int c, t;
findtabcomma(filenam, &c, &t);
printf("Commas: %d\nTabs: %d", c, t);
And in C++, you can use reference variables. So the findtabcomma function could be rewritten as:
void findtabcomma(const char *fn, int &ncomma, int &ntab)
{
FILE *fp;
int c;
if (fp = fopen(fn, "r")) {
while ((c = getc(fp)) != EOF) {
if (c == '\t')
++ntab;
if (c == ',')
++ncomma;
}
fclose(fp);
}
}
And used like this:
int c, t;
findtabcomma(filenam, c, t);
printf("Commas: %d\nTabs: %d", c, t);
Notice how there are no more *s and &s with C++ references.

Answer 3

You can create a function that either returns an array of type int of size 2 such as
int* functionName(arg1, arg2)
array[0] = totalScore;
array[1] = totalPoints;
return array;
or you could pass in the values by reference by doing something like
void functionName(&arg1, &arg2)
What passing by reference does is it passes the ADDRESS of the variable and then modifies the variable directly instead of creating a copy and passing it into the function.

Answer 4

You can use reference in the argument list to return data
int fun(); can be coded as void fun(int& )