Thread: passing structure to function

Hey all, thanks for the help (again)

I'm just returning link.year to try and get a working number after the function is called but it won't work. Do I somehow need to add link.year inside the struct_function function to initialize link.year, it's returning as '0' when i run the program no matter what yyyy I insert.

I will be coding the forumla inside the struct_function function once i can see that all the structure variables date_one.month, date_one.day, date_one.year can be activated through the printf function after I run the program. Thanks for the help

This

Code:

// EX_2.c  Chapter 8 Exercise #2
// compute two date
// August 8, 2014
// February 22, 2015


#include <stdio.h>


struct my_struct
{
    int month;
    int day;
    int year;
};


int main(void)
{    
    int struct_function (struct my_struct link);


    struct my_struct date_one, date_two;


    printf("Enter date #1: (mm dd yyyy): ");
    scanf("%i/%i/%i", &date_one.month, &date_one.day, &date_one.year);
    
    /*
    printf("Enter date #2: (mm dd yyyy): ");
    scanf("%i/%i/%i", &date_two.month, &date_two.day, &date_two.year);
    */


    // return integer
    
    printf("%i\n", struct_function(date_one));


    //    printf("%i", struct_function(date_two));
    
    return 0;
}


int struct_function (struct my_struct link)
{
    // N = 1461 * f(year, month) / 4 + 153 * g(month) / 5 + 3;`


    int sum; 


    if (link.month <= 2)
    {
        link.year -= 1;
        link.month += 13;
    }


    else if (link.month > 2)
    {
        link.year = link.year;    
        link.month += 1;
    }
    


    return link.year;
}

You're probably entering the date as mm dd yyyy, but the scanf format ("%i/%i/%i") wants it as mm/dd/yyyy. You can check the return value of scanf() to see how many numbers it actually scanned.

Originally Posted by Hodor

You're probably entering the date as mm dd yyyy, but the scanf format ("%i/%i/%i") wants it as mm/dd/yyyy. You can check the return value of scanf() to see how many numbers it actually scanned.

that worked thanks I fixed the scanf function call

Here's my finished code right here i think I found a typo in the book there is more than one so far I've found. The end of the formula "+ day" makes the calculation not add up correctly for the dates specified in the book, for august 8 2004 and February 22 2005 (this is date_one.day in struct_function function). Thanks!

Code:

// EX_2.c  Chapter 8 Exercise #2
// compute two date
// August 8, 2014
// February 22, 2015


#include <stdio.h>


struct my_struct
{
	int month;
	int day;
	int year;
};


int main(void)
{	
	int struct_function (struct my_struct link);


	struct my_struct date_one, date_two;


	printf("Enter date #1: (mm dd yyyy): ");
	scanf("%i %i %i", &date_one.month, &date_one.day, &date_one.year);
	
	printf("%i\n", struct_function(date_one));


	printf("Enter date #2: (mm dd yyyy): ");
	scanf("%i %i %i", &date_two.month, &date_two.day, &date_two.year);


	printf("%i\n", struct_function(date_two));


	printf("RESULT: \n");
	
	int aa, bb, result;


	aa = struct_function(date_one);
	bb = struct_function(date_two);


	result = aa - bb;


	printf("%i days\n", result);


	return 0;
}


int struct_function (struct my_struct link)
{
	// N = 1461 * f(year, month) / 4 + 153 * g(month) / 5 + days;


	int sum; 


	if (link.month <= 2)
	{
		link.year -= 1;
		link.month += 13;
	}


	else if (link.month > 2)
	{
		link.month += 1;
	}
	
	int a, b;


	a = (1461 * link.year) / 4;
	b = (153 * link.month) / 5 + link.day;


	sum = a + b;


	return sum;
}

Is it possible that in the computation of "b" you want to divide the first term by 5 + link.day, not just by 5?

By the way you really should be using more descriptive variable and function names.

I think he want's to calculate the day of the week given by a date, or the Date of Easter Sunday given by a year. May be according the formula of Zeller's congruence, Butcher or Gauss. But it looks like Zeller's congruence.
Is this correct _jamie?

I hope you can find a PDF-file in the Attachment with several formulas.
The file is written in german. But i still hope, it can help you.

my code works, i just switched the

Code:

result = bb - aa;

line around because I was getting a negative number. For example, inserting two dates, i.e. 7 27 2016 and 7 28 2016 results in the program executing and displaying "1 days".

rusyoldguy, i didn't understand the Zeller's congruence formula after a quick view, the formula is in the code

Code:

// N = 1461 ...

The programming book just names the formula by "formula" and says write a program using the formula that calculates the days between dates using a date structure returning the value of N computed.

Thanks!

Hodor:

Code:

// EX_4.c


#include <stdio.h>


struct day
{
	int numbers;
	char letter[15];
};


struct my_struct
{
	int month;
	int day;
	int year;
};


int main(void)
{	
	int struct_function (struct my_struct link);
	int aa;


	struct my_struct date_one;


	// array of structures


	const struct day days[7] = { { 6, { 'S', 'u', 'n', 'd', 'a', 'y' } },
		{ 5, { 'M', 'o', 'n', 'd', 'a', 'y' } },
		{ 7, { 'T', 'u', 'e', 's', 'd', 'a', 'y' } },
		{ 9, { 'W', 'e', 'd', 'n', 'e', 's', 'd', 'a', 'y' } },
		{ 8, { 'T', 'h', 'u', 'r', 's', 'd', 'a', 'y' } },
		{ 6, { 'F', 'r', 'i', 'd', 'a', 'y' } },
		{ 8, { 'S', 'a', 't', 'u', 'r', 'd', 'a', 'y' } } };




	printf("Enter a date: (mm dd yyyy): ");
	scanf("%i %i %i", &date_one.month, &date_one.day, &date_one.year); // get date_one (first date)


	aa = struct_function(date_one);


	printf("%i\n", aa);


	int x, i;


	x = (aa - 621049) % 7;


	for (i = 0; i <= days[x].numbers; ++i)
		printf("%c", days[x].letter[i]);


	printf("\n");


	return 0;
}
	


int struct_function (struct my_struct link)
{
	// N = 1461 * f(year, month) / 4 + 153 * g(month) / 5 + day;


	int sum;


	if (link.month < 3)
	{
		link.month += 12;
		link.year -= 1;
	}


	sum = link.day + (153 * link.month - 457) / 5  + 365 * link.year + link.year / 4 - link.year / 100 + link.year / 400 - 306;


	return sum;
}

Code:

$ ./EX_4 
Enter a date: (mm dd yyyy): 2 20 2008
733092
Monday

The output for February of 2008 doesn't show the 20th day is a Monday so i'm thinking your formula is wrong, or what is wrong here? Thanks!

It's probably to also good to note that the formulas in the book give the incorrect day of the week number as well for some years. For example, using the book's formulas it says that 1 March 2100 is a Tuesday, which is incorrect. My implementation using Baum's formula's correctly gives the day as a Monday. (this is also why the book is broken for date ranges, for the other exercise, that include centuries that are not evenly divisible by 400; e.g. the book is treating the year 2100 as a leap year when it's not, but 2000 is)

Thank you for time & effort Hodor.