C++ - Repeat std::getline() as user integer input? [closed] - c++

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How to repeat std::getline() as user number input like this method:
std::string num;
std::cout << "How many subjects you want to sum: ";
std::getline (std::cin,num);
Then take user number input and repeat std::getline() many times as input to sum all the subjects marks user will input them after the first questions.

Answer 1

Prefer not to use std::getline for inputting numbers.
You need a standard pattern:
int quantity = 0;
std::cout << "Enter quantity of subjects to sum: ";
std::cin >> quantity;
int sum = 0;
for (int i = 0; i < quantity; ++i)
{
int value;
std::cin >> value;
sum += value;
}
A common data input format is to specify the quantity as the first number on a single line.
The data will follow on subsequent lines, usually one number per line.
The operator>> will skip whitespace (including newlines).
Edit 1: Using getline
If you must use getline, remember that it only reads in strings (characters). If you want to numbers, you will have to convert from text representation to internal representation.
int quantity;
std::string text_line;
std::cout << "Enter quantity to sum: ";
std::getline(std::cin, text_line);
int sum = 0;
// Extract number from the text
{
std::istringstream text_stream(text_line);
text_stream >> quantity;
}
for (int i = 0; i < quantity; ++quantity)
{
std::getline(std::cin, text_line);
std::istringstream text_stream(text_line);
int value = 0;
text_stream >> value;
sum += value;
}
Notice the difference in the number of lines.
Also, notice the usage of std::istringstream. It looks like using std::cin in the first example.
There are other techniques to convert text representation of numbers to internal representation. These are left to the reader to research.