Universal Number?

[wilkejon000]

Hello, I am creating a gradebook calculator. I am trying to make it so that anything entered for Grade1 has to be a number. Is there a variable or value I can use to represent all numbers to replace x?

std::cout << "Welcome to the Grade Calculator. What is your first number grade? " << std::endl;
std::cin >> Grade1;
if (Grade1 != x)
std::cout << "That is not an acceptable number. Please double-check your typing and try the program again." << std::endl;
return 1;

[jonnin]

No. There is a numerical limitations file, so that things that cannot be represented (like 1 million factorial) in standard variable types can be checked somewhat.

But you are asking for a logical test in a single value, and that isnt possible. Most likely, there is a valid range of input, like 0 to 100, or if you allow bonus points, maybe 0 to 125 where these are typical school grades representing a %.

There are no unsigned floating point types, so if you need decimal accuracy, you need a double.
If you are working in whole numbers, an unsigned char will work, an you can check it:
if(Grade1 <125 && Grade1 >= 0)
.... handle error..
etc

you can do the same for floating point... just be a little more precise (no real effect but its better code as it tells the user that Grade1 should be a floating point).
if(Grade1 < 125.0 && Grade1 >= 0.0)

with a bit of odd coding you could probably express this as a value such that your example code would work, but it would be a strange thing to do.

[JLBorges]

#include <iostream>

int main()
{
    const int MIN_GRADE = 0 ;
    const int MAX_GRADE = 100 ;

    int grade_1 ;
    std::cout << "Welcome to the Grade Calculator. What is your first number grade?\n"
                 "please enter a value in the range [" << MIN_GRADE << ',' << MAX_GRADE << "]: " ;

    if( std::cin >> grade_1 ) // if the user entered a valid integer
    {
        // proceed with processing the input
        if( grade_1 >= MIN_GRADE && grade_1 <= MAX_GRADE ) // the value within range
        {
            // do something with the entered grade
            // ...
        }

        else // integer was input, but it is out of range
        {
            std::cout << "the value you entered is out of range\n"
                         "please try the program again.\n" ;
            return 1 ;
        }
    }

    else // the user did not enter a sequence of characters that formed an integer
    {
        std::cout << "That is not an acceptable number.\nPlease double-check your"
                     " typing and try the program again.\n" ;
        return 1 ;
    }
}