How can i perform this loop thing in switch-case in C. I Want to print that the student got A grade-CodePudding

int user_marks;
printf("Enter your obatined marks to know your grade: ")
scanf("%d", &user_marks);

switch (user_marks)
{
case user_marks>=90 && user_marks<=100:
    printf("Your grade is A.");
    break;


default:
    printf("Enter valid marks.");
    break;
}

I want to print that the user got an A grade if they enter numbers between 90 and 100 including those values in the "case" section of the code.

CodePudding user response：

cant use switch, use if / else

int user_marks;
printf("Enter your obatined marks to know your grade: ")
scanf("%d", &user_marks);

if(user_marks>=90 && user_marks<=100){
    printf("Your grade is A.");
} else {
    printf("Enter valid marks.");
}

CodePudding user response：

The case labels must use integer constant expressions. This means that the result of these expressions must be known at compile-time. However, the value of user_marks is not known at compile-time.

Even if user_marks were an integer constant, the line

case user_marks>=90 && user_marks<=100:

would still be wrong, because, depending on the value of user_marks, the expression user_marks>=90 && user_marks<=100 would evaluate to either 0 (false) or 1 (true), so the entire line would be equivalent to either

case 0:

case 1:

which is not what you want.

Therefore, if you really wanted to use a switch statement, you would have to do the following instead:

switch (user_marks)
{
    case 90:
    case 91:
    case 92:
    case 93:
    case 94:
    case 95:
    case 96:
    case 97:
    case 98:
    case 99:
    case 100:
        printf("Your grade is A.");
        break;

    default:
        printf("Enter valid marks.");
        break;
}

However, it is simpler to use an if...else statement instead:

if ( user_marks >= 90 && user_marks <= 100 )
{
    printf( "Your grade is A." );
}
else
{
    printf( "Enter valid marks." );
}

CodePudding user response：

When the source data is particularly well understood, a "hashing function" can be used to determine a quality of that data.

The problem stated "only 90-100" are equivalent to "A", and the desire to use a switch() statement.

The following tests several values in sequence, hashing them to a constant. (It's expected that values won't be greater than 100.

int my_main() {

    int marks[] = { 70, 85, 89, 90, 94, 100 };

    for( int i = 0; i < sizeof marks/sizeof marks[0] ; i   ) {
        int mark = marks[i];

        // hash:
        // leading 9 or 10 plus 1 => 10 or 11
        // integer divide by 2 of result => 5
        switch( ((mark / 10)   1) / 2 ) {
            case 5:
                printf( "%d is worth an A\n", mark );
                break;
            default:
                printf( "%d is NOT worth an A\n", mark );
                break;
        }
    }
    return 0;
}

Output

70 is NOT worth an A
85 is NOT worth an A
89 is NOT worth an A
90 is worth an A
94 is worth an A
100 is worth an A

A simple if/else would be easier and clearer, of course...