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I am using a function to check that my input in an integer only:

 int input; while (true) { std::cin >> input; if (!std::cin) { std::cout << "Bad Format. Please Insert an integer! " << std::endl; std::cin.clear(); std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n'); continue; } else return input; }

However when inputing a integer followed by a char, eg. 3s, the integer gets accepted and the message gets printed.

How can I make sure that the input in such format does not get accepted, nor do input in form 4s 5, so when the integer appears after the space.

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  • std::getline and unsure parsed line is empty afterward? Commented May 27, 2020 at 7:43
  • 1
    char is also an int Commented May 27, 2020 at 7:44
  • 1
    std::cin into a string and validate the string using regex or something. Commented May 27, 2020 at 7:44

2 Answers 2

Reset to default
5

That happens because chars in c++ are represented by their numeric value in the ascii table, you can try regular expressions like this:

#include <regex> #include <string> std::string str; std::regex regex_int("-?[0-9]"); while (true) { std::cin >> str; if (regex_match(str, regex_int)) { int num = std::stoi(str); //do sth break; } }
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2 Comments

Fixed the problem Thank you.
"That happens because chars in c++ are represented by their numeric value" No, here, the issue is that std::cin >> input; stops once int has been read (so it remains extra char in std::cin).
0

There's no need for a regular expression that duplicates the validation that std::stoi does. Just use std::stoi:

std::string input; std::cin >> input; std::size_t end; int result = std::stoi(input, &end); if (end != input.size()) // error
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