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  1. #include <iostream>
  2. #include <stdlib.h>
  3. #include <limits>
  4.  
  5. bool invalid_input(std::istream& in) {
  6.     return in.rdstate() == std::ios::failbit;
  7. }
  8.  
  9. std::istream& get_single_grade(std::istream& in, int& grade) {
  10.     std::cout << "Please enter a grade value between 0 and 100." << "\n";
  11.     if (in >> grade) {
  12.         if(grade<0 || grade>100)
  13.             in.setstate(std::ios::failbit);
  14.     }
  15.     return in;
  16. }
  17.  
  18. bool get_grade(std::istream& in, int &grade) {
  19.     while(invalid_input(get_single_grade(in, grade))) { //while we failed to get data
  20.          in.clear(); //clear the failure flag
  21.          //ignore the line that the user entered, try to read the next line instead
  22.          in.ignore(std::numeric_limits<std::streamsize>::max(),'\n'); 
  23.     }
  24.     return in.good();
  25. }
  26.  
  27. int main(int argc, char* argv[])
  28. {    
  29.     int grade = -1; // grade will hold grade value; initialized to -1
  30.     if (get_grade(std::cin, grade) == false) {
  31.         std::cerr << "unxpected EOF or stream error!\n";
  32.         return false;
  33.     }    
  34.     std::cout << grade << "\n";
  35.     return EXIT_SUCCESS;
  36. }
Success #stdin #stdout #stderr 0s 3344KB
comments (?)
stdin 
A
stdout 
Please enter a grade value between 0 and 100.
Please enter a grade value between 0 and 100.
stderr 
unxpected EOF or stream error!
https://ideone.com/2tcPfE
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
secret

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