Is there a simpler way to write this? - c++

Question

Hi I'm learning the basic of C++ and I'm in the process of doing an assignment. I'm asking if there is a simpler way to write this part.
if ( 100 >= projectgrade && 0<= projectgrade ) {}
else
{
cout<<endl<<"invalid data, please retry again.";
cin.ignore();
cin.get();
return EXIT_SUCCESS;
}
if ( 100 >= midtermgrade && 0<= midtermgrade ) {}
else
{
cout<<endl<<"invalid data, please retry again.";
cin.ignore();
cin.get();
return EXIT_SUCCESS;
}
if ( 100 >= finalexamgrade && 0<= finalexamgrade ) {}
else
{
cout<<endl<<"invalid data, please retry again.";
cin.ignore();
cin.get();
return EXIT_SUCCESS;
}
Is it possible to write all those restriction in one bracket of if? I try numerous time but I can't figure it out. Ty for helping out!

Answer 1

Well, if you examine your logic it's if any of the grades is less then 0 or greater then 100, so something like this -
if ( projectgrade < 0 || projectgrade > 100 ||
midtermgrade < 0 || midtermgrade > 100 ||
finalexamgrade < 0 || finalexamgrade > 100
) {
cout<<endl<<"invalid data, please retry again.";
cin.ignore();
cin.get();
return EXIT_SUCCESS;
}
Edit
and we could always add a #define like
#define range(x) x < 0 || x > 100
then that if could be shortened to
if (range(projectgrade) || range(midtermgrade) || range(finalexamgrade))

Answer 2

if ( (projectgrade <0) || (projectgrade > 100) || (midtermgrade <0) || (midtermgrade > 100) || (finalexamgrade < 0) || (finalexamgrade > 100))
{
cout<<endl<<"invalid data, please retry again.";
cin.ignore();
cin.get();
return EXIT_SUCCESS;
}

Answer 3

In C++11 you can write:
auto failure = [](){
cout << "invalid data, please try again" << endl;
cin.ignore();
cin.get();
return 0;
};
and then use it when failures happen:
if ( !(100 >= projectgrade && 0<= projectgrade) )
return failure();
// do more stuff
if ( !(100 >= midtermgrade && 0<= midtermgrade) )
return failure();
Note, doing endl after your text instead of before it is preferable; return 0; always indicates success, and cin.ignore() just ignores a single character (in general, you may want to ignore the rest of the line).

Answer 4

First you may add a function for the test
bool is_valid_grade(int grade)
{
return 0 <= grade && grade <= 100;
}
or
bool is_valid_grade(unsigned int grade)
{
return grade <= 100; // unsigned cannot be negative
}
then use it like:
if (is_valid_grade(projectgrade)
&& is_valid_grade(midtermgrade)
&& is_valid_grade(finalexamgrade))
{
// Valid code
}
else
{
return failure(); // your previous code into a function
}