Reputation: 25
for loop with invalid error and looping questions
I am fairly new to C++, I am trying to write a code that allows input number of reviewers then allows number of reviewers to enter movie rating and display asterisks based on the number input. I am having difficulty incorporating an if statement that display "Movie ratings must be from 1 to 5." when the user input any number that's outside of 1 to 5. Another thing when it does work, it still continues the for loop of cout << "\nReviwer " << r << " rating: " ; instead of stopping and restarting. Any assistance is appreciated. complied code
int reviewers;
int rating;
//input how many reviewers will be reviewing
cout << "How many reviewers? ";
cin >> reviewers;
cout << "Movie ratings must be from 1 to 5." << endl;
for (int r = 1; r <= reviewers; r++) {
cout << "\nReviwer " << r << " rating: ";
cin >> rating;
if (rating < 1 || rating > 5)
cout << "Movie ratings must be from 1 to 5." << endl;
else {
for (int j = 1; j <= rating; j++) {
cout << "* ";
} //end for
cout << endl;
} //end if
} //end for
Output example should be like this
Upvotes: 2
Views: 142
Answers (5)
Reputation: 23832
You'd want to keep asking the number of stars if the user inputs a value outside the range, something like:
for (int r = 1; r <= reviewers; r++)
{
cout << "\nReviwer " << r << " rating: ";
do
{
cin >> rating;
if (rating < 1 || rating > 5) // print error message
cout << "Movie ratings must be from 1 to 5." << endl;
} while (rating < 1 || rating > 5); // repeat the loop if out of range
for (int j = 1; j <= rating; j++)
{
cout << "* ";
} //end for
cout << endl;
}
Note that you should be doing input validation also, e.g., if the input is an alphabetic character, your code will trigger an infinite loop, here an example of a possible solution:
#include <limits>
//...
do
{
if (!(cin >> rating))
{
std::cout << "Bad input, try again";
cin.clear(); //clear error flags
cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n'); // clear buffer
rating = 0;
}
if (rating < 1 || rating > 5)
cout << "Movie ratings must be from 1 to 5." << endl;
} while (rating < 1 || rating > 5);
Upvotes: 1
Reputation: 51
Here is some code I quickly put together. I hope the comments are useful and if you have any questions just ask!
The main part is the recursive function get_ratings which will loop forever until it returns 1
// All this function does is returns the correct amount of stars
// E.G. make_stars(4) returns " * * * *"
string make_stars(int star_Count) {
string stars;
for (int i = 0 ; i < star_Count ; i++) {
stars += " *";
}
return stars;
}
// We get the ratings and returns 1 or 0 depending of it succeeded or failed
int get_ratings(int reviewer_count) {
// We initialise the ratings integer
int rating;
// We loop through all reviewers
for (int i = 0 ; i < reviewer_count ; i++) {
// We do i + 1 so it is more readable (usually in English we start at 1 not 0 like computers)
cout << "What is reviewer " << (i + 1) << "'s rating?" << endl;
//We get the user input
cin >> rating;
// We check to see if rating is withing the range. We could also do is NOT in the range and flip line 27 and 29
if (1 <= rating && rating <= 5) {
// If it is within range we will print the correct amount of stars
cout << make_stars(rating) << endl;
} else {
// We return 0 so we can determine the function "failed"
return 0;
}
}
// We return 1 so we can determine the function "succeeded"
return 1;
}
// This is a recursive function (it can run itself)
int get_ratings_rec(int reviewers) {
cout << "All ratings must be given between 1 and 5 (inclusive)" << endl;
// get_ratings_status is equal to 1/0 depending on if get_ratings() succeeded or failed
int get_ratings_status = get_ratings(reviewers);
if (get_ratings_status == 1) {
// If it was a success we print "Success!"
cout << "Success!" << endl;
} else {
// If it was a failure we tell the user and run get_ratings_loop() again until it succeeds
cout << "Failed, please try again\n" << endl;
get_ratings_loop(reviewers);
}
}
// Our main entry point to the program
int main() {
// We initialise the reviewers integer
int reviewers;
cout << "How many reviewers?\n>>> " << endl;
cin >> reviewers;
// We run get_ratings_loop() with the integer given
get_ratings_loop(reviewers);
}
Upvotes: 1
Reputation: 240
You should have
#include <iostream>
#include <string>
using namespace std;
int main(){
int reviewers;
int rating;
//input how many reviewers will be reviewing
cout << "How many reviewers? ";
cin >> reviewers;
cout << "Movie ratings must be from 1 to 5." << endl;
for (int r = 1; r <= reviewers; r++) {
cout << "\nReviwer " << r << " rating: ";
cin >> rating;
while (rating < 1 || rating > 5){
cout << "Movie ratings must be from 1 to 5." << endl;
cout << "\nReviwer " << r << " rating: ";
cin >> rating;
}
if (rating >= 1 && rating <=5){
for (int j = 1; j <= rating; j++) {
cout << "* ";
} //end for
cout << endl;
} //end if
} //end for
}
};
It's not optimised but do the trick
Upvotes: 1
Reputation: 7774
I suppose you aim at something like this:
int reviewers;
int rating;
//input how many reviewers will be reviewing
cout << "How many reviewers? ";
cin >> reviewers;
cout << "Movie ratings must be from 1 to 5." << endl;
for (int r = 1; r <= reviewers; r++) {
while(true) {
cout << "\nReviewer " << r << " rating: ";
cin >> rating;
if (rating < 1 || rating > 5) {
cout << "Movie ratings must be from 1 to 5." << endl;
} else {
break;
}
}
for (int j = 1; j <= rating; j++) {
cout << "* ";
} //end for
cout << endl;
} //end for
Upvotes: 1
Reputation: 76
if your mean is the reviewer must input the number between 1 and 5, you can use a do while loop like this:
do
{
//enter rating;
}while (rating < 1||rating >5);
//print out rating;
Upvotes: 1