How to Get a Variable from my MAIN function to another function?

This is a discussion on How to Get a Variable from my MAIN function to another function? within the C Programming forums, part of the General Programming Boards category; I am defining a variable n using scanf in my main function. will the rest of my program know it? ...

  1. #1
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    How to Get a Variable from my MAIN function to another function?

    I am defining a variable n using scanf in my main function. will the rest of my program know it?

    I am solving an equation and have a square root part of my function that sends back the square root value to my main function.

    Code:
    double getSquareRoot ( void ); 
    
    
    int main(void)
    {
            double n_factorial; // powers multipled by the solved square root
    
    
            printf("ESTIMATE A FACTORIAL NUMBER\n");
            printf("This program was written by %s.\n", PROGRAMMER_NAME);
    
    
            printf("Please enter a positive integer: "):
            scanf("%lf", &n);
    
    
            sqrt_partial = (2.0 * n) + (1.0 + 3.0);
    
    
            sqrt_solved = getSquareRoot( );       
       
            n_factorial = pow(n,n) * exp(-n) * sqrt_solved;
            printf("%.0f! equals approximately %.5f \n", n, n_factorial);
    
    
    return EXIT_SUCCESS;
    }
    
    
    double getSquareRoot (void)
    {
            double n; // User defines the factorial
            double sqrt_partial; 
            double sqrt_solved;
    
    
            printf("Please enter a positive integer: "):
            scanf("%lf", &n);
    
    
            sqrt_partial = (2.0 * n) + (1.0 / 3.0);
    
    
            sqrt_solved = sqrt(sqrt_partial * PI);
    
    
            retun sqrt_solved;
    }

  2. #2
    SAMARAS std10093's Avatar
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    You have to learn what the arguments of a function are.
    You wrote
    Code:
    double getSquareRoot (void)
    ,where the void declares that this function has no arguments at all.When you want to pass an argument you have to write something like this
    Code:
    double getSquareRoot (typeOfArgument argumentName)
    In your case you have a variable called n...but oops!You have not declare it!This is not f#,you have to say to the compiler the type of the variable.int is a probably good choice for n in this case.
    So you can write
    Code:
    double getSquareRoot (int n)
    Now n is visible by the body of getSquareroot.In other words ,n lives now and in the world of the function(not only in the world of main).

    You could also set is a global variable ,but this is a really bad practice,especially if you are going to write a large program in the future.

  3. #3
    and the hat of wrongness Salem's Avatar
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    > n_factorial = pow(n,n) * exp(-n) * sqrt_solved;
    You see how you use n here.

    > sqrt_solved = getSquareRoot( );
    How about trying
    sqrt_solved = getSquareRoot( n );
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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