Thread: writing a pair of numbers to an array

Use a struct.

You can use a struct "straight" up, or with a typedef "chaser". For this example, try one straight up:

Code:

struct mystruct {  //mystruct is the name for the *definition* of this struct
   double x;
   double y;
} NameofStruct; //NameofStruct is the name for the first declaration or instance, of this struct.

Now make an array of that type of struct, and you're good to go. You'll use the "." operator, to access the x and the y portions of it.

You'll really be moving your programming skills up a big jump, with this. It's the right way to go, however.

Heres the code so far:

Code:

#include <stdio.h>

//function prototype
int read_location(double *x, double *y);

struct coordinates {
	double x;
	double y;
};


int main ()
{
 	int choice;	
	struct coordinates table[19];
	read_location;

	//loop menu as long as valid option is chosen
	do
	{
		printf("Please choose one of the following actions:\n");
		printf("1.) Quit\n");
		printf("2.) Sort by x:\n");
		printf("3.) Sort by y:\n");
		printf("4.) Sort by distance:\n");
		printf(":");
		scanf("%d", &choice);
		switch(choice)
		{
			case 1:
				return 0;
			case 2:
				//sort by x
				break;
			case 3:
				//sort by y
				break;
			case 4:
				//sort by distance between two points
				break;
			}
	} while (choice <=4);

	return 0;
}



int read_location(double *x, double *y)
{
	printf("Enter x:\n");
	scanf("%lf", &x);
	printf("Enter y:\n");
	scanf("%lf", &x);
}

Also im compiling this on linux using gcc, not sure if that matters or not just throwing that out there.

I think I got it now, but before I continue can you guys take a look at it and let me know if im on the right track? Now it allows me to read the numbers before it goes to the menu, but im not sure how to stick it into an array.

Code:

#include <stdio.h>

//function prototype
int read_location(double *x, double *y);

struct coordinates
{
	double x;
	double y;
};

struct coordinates number1;

int main ()
{
 	struct coordinates *heyyo;
        heyyo = &number1;
        number1.x=0;
        number2.y=0;
        int choice;	
	double num1, num2;
	struct coordinates table[19];
	read_location(&num1, &num2);

	//loop menu as long as valid option is chosen
	do
	{
		printf("Please choose one of the following actions:\n");
		printf("1.) Quit\n");
		printf("2.) Sort by x:\n");
		printf("3.) Sort by y:\n");
		printf("4.) Sort by distance:\n");
		printf(":");
		scanf("%d", &choice);
		switch(choice)
		{
			case 1:
				return 0;
			case 2:
				//sort by x
				break;
			case 3:
				//sort by y
				break;
			case 4:
				//sort by distance
				break;
			}
	} while (choice <=4);

	return 0;
}


int read_location(double *x, double *y)
{
	printf("Enter x:\n");
	scanf("%lf", &number1.x);
	printf("Enter y:\n");
	scanf("%lf", &number1.y);
}

Code:

int read_location(double *x, double *y)
{
	printf("Enter x:\n");
	scanf("%lf", &number1.x);
	printf("Enter y:\n");
	scanf("%lf", &number1.y);
}

This function should work one of two ways:

1 - Pass it a pointer to a structure, and fill it in.
2 - Pass it pointers to individual doubles, and fill those in.

You are doing half of each.

Code:

void foo( stuct bar *baz )
{
    read into baz->x;
    read into baz->y;
}

Or...

Code:

void foo( double *bar, double *baz )
{
    read into bar
    read into baz
}

If doing the latter, you need to assign those values to your structure (or pass the structure's elements individually). That might be done like so:

Code:

foo( &astruct.x, &astruct.y );

Or perhaps...

Code:

foo( &x, &y );
astruct.x = x;
astruct.y = y;

Pick one.


Quzah.

You have the right idea and syntax.

Originally Posted by laserlight

You have the right idea and syntax.

Im getting a "coordinates undeclared, first use in function" error when I try to compile it.

I changed it to:

read_location(&number1.x, &number1.y);

it compiles fine but im not sure if thats the same thing or not