Thread: Help needed :-(

Can you help me understand why I keep getting this error message when I compile this code? The error message is: determine_grade redefinition different basic types.

Code:

#include <stdio.h>
				   
int main(void)
{
	// declaring variables
	float test_1,
		test_2,
		test_3,
		test_4,
		test_5;
	char letter_1,
		letter_2,
		letter_3,
		letter_4,
		letter_5;
	float test_average;

	// printing a safe-entry message for the user
	printf("WARNING! Only values between 0-100 are valid.\n");
	
	// asking the user for the test scores
	printf("Test 1: ");
	scanf("%f", &test_1);
	printf("Test 2: ");
	scanf("%f", &test_2);
	printf("Test 3: ");
	scanf("%f", &test_3);
	printf("Test 4: ");
	scanf("%f", &test_4);
	printf("Test 5: ");
	scanf("%f", &test_5);

	// passing the arguments to the calc_average function
	test_average = calc_average(test_1, test_2, test_3, test_4, test_5);

	// passing the arguments to the determine_grade function
	letter_1 = determine_grade(test_1);
	letter_2 = determine_grade(test_2);
	letter_3 = determine_grade(test_3);
	letter_4 = determine_grade(test_4);
	letter_5 = determine_grade(test_5);

	// printing the test scores, equivalent letters, and
	// the test average and its letter on the screen
	printf("\n%.2f\t%c\n", test_1, determine_grade(letter_1));
	printf("%.2f\t%c\n", test_2, determine_grade(letter_2));
	printf("%.2f\t%c\n", test_3, determine_grade(letter_3));
	printf("%.2f\t%c\n", test_4, determine_grade(letter_4));
	printf("%.2f\t%c\n", test_5, determine_grade(letter_5));
	printf("Test Average: %.2f\t%c\n", test_average, determine_grade(test_average));

}

// declaring the calc_average function
float calc_average(float, float, float,
				   float, float);
float calc_average(float score_1, float score_2, float score_3,
				   float score_4, float score_5)
{
	float average;

	average = (score_1 + score_2 + score_3 + score_4 + score_5) / 5.0;

	return average;
}

// declaring the determine_grade function
char determine_grade(float);
char determine_grade(float test_score)
{
	if (test_score >= 90 && test_score <= 100)
		return 'A';
	else if (test_score >= 80 && test_score <= 89)
		return 'B';
	else if (test_score >= 70 && test_score <= 79)
		return 'C';
	else if (test_score >= 60 && test_score <= 69)
		return 'D';
	else if (test_score >= 0 && test_score < 60)
		return 'F';
}

Code:

char determine_grade(float);

Move that forward declaration up above the main() function. You are attempting to call determine_grade() in the main() function, but it isn't defined yet!

char determine_grade(float);
char determine_grade(float test_score)

That first line needs to appear before the main() function in the code.

To be safe, shouldn't all function declarations go above main? Meaning this too should go up top for safety's sake:

Code:

// declaring the calc_average function
float calc_average(float, float, float,
				   float, float);

Okay, I did. I tried to move both of the statements declaration for both of the functions, but now the compiler says: determine_grade not all control paths return a value. :-(

Originally Posted by adrian.mowrey

Okay, I did. I tried to move both of the statements declaration for both of the functions, but now the compiler says: determine_grade not all control paths return a value. :-(

What if test_score is -15 ?

I haven't gotten to the error handling part. I printed a message to let the user know that values between 0-100 are valid. But I don't understand why the compiler says that not all control paths return a value.

Originally Posted by adrian.mowrey

I don't understand why the compiler says that not all control paths return a value.

Nothing gets returned by determine_grade if test_score is below zero.

Two options the way I see it:
Change the last else if just just an else.
or...
Append a final else, and have a special character for an error(perhaps 'E' or '!')



edit: Elysia explained it maybe a bit better than me

Return '?'. That's easy for the user. Else s/he will only see some random crap.

Okay, this worked.

Code:

/*
Chapter: 3
Exercise: 7
Author: Adrian Gheorghe Mowrey
*/

#include <stdio.h>

float calc_average(float, float, float,
				   float, float);

char determine_grade(float);

int main(void)
{
	// declaring variables
	float test_1,
		test_2,
		test_3,
		test_4,
		test_5;
	char letter_1,
		letter_2,
		letter_3,
		letter_4,
		letter_5;
	float test_average;

	// printing a safe-entry message for the user
	printf("WARNING! Only values between 0-100 are valid.\n");
	
	// asking the user for the test scores
	printf("Test 1: ");
	scanf("%f", &test_1);
	printf("Test 2: ");
	scanf("%f", &test_2);
	printf("Test 3: ");
	scanf("%f", &test_3);
	printf("Test 4: ");
	scanf("%f", &test_4);
	printf("Test 5: ");
	scanf("%f", &test_5);

	// passing the arguments to the calc_average function
	test_average = calc_average(test_1, test_2, test_3, test_4, test_5);

	// passing the arguments to the determine_grade function
	letter_1 = determine_grade(test_1);
	letter_2 = determine_grade(test_2);
	letter_3 = determine_grade(test_3);
	letter_4 = determine_grade(test_4);
	letter_5 = determine_grade(test_5);

	// printing the test scores, equivalent letters, and
	// the test average and its letter on the screen
	printf("\n%.2f\t%c\n", test_1, letter_1);
	printf("%.2f\t%c\n", test_2, letter_2);
	printf("%.2f\t%c\n", test_3, letter_3);
	printf("%.2f\t%c\n", test_4, letter_4);
	printf("%.2f\t%c\n", test_5, letter_5);
	printf("Test Average: %.2f\t%c\n", test_average, determine_grade(test_average));

}

// declaring the calc_average function
float calc_average(float score_1, float score_2, float score_3,
				   float score_4, float score_5)
{
	float average;

	average = (score_1 + score_2 + score_3 + score_4 + score_5) / 5.0;

	return average;
}

// declaring the determine_grade function
char determine_grade(float test_score)
{
	if (test_score >= 90 && test_score <= 100)
		return 'A';
	else if (test_score >= 80 && test_score <= 89)
		return 'B';
	else if (test_score >= 70 && test_score <= 79)
		return 'C';
	else if (test_score >= 60 && test_score <= 69)
		return 'D';
	else (test_score >= 0 && test_score  < 60);
		return 'F';
}

Thank you "crowe," and of course everybody else for the replies. ;-) I didn't need anything to handle the errors, I just needed to demonstrate the purpose of functions and how to return values back, etc. Thank you again! :-D

Originally Posted by adrian.mowrey

Okay, this worked.

Code:

	else (test_score >= 0 && test_score  < 60);

This is wrong. else is the final result. As in, if none of the other conditions evaluate to true, then you do this. So you shouldn't have an expression there.

Code:

	else
		return 'F';

Still, this isn't really the best solution. You'd probably want to do it more like:

Code:

...
	else if (test_score >= 0 && test_score < 60)
		return 'F';
	else
		return '?';

That would handle values both above 100 and below 0.


One more thing to consider: Multiple returns are generally considered a no-no.