Thread: writing a pair of numbers to an array

perhaps it's time to post the updated code

Originally Posted by wankel

will "struct coord hold;" do the trick? Im currently using that right now and its giving me the same error so I think im doing it wrong haha

EDIT: nevermind, that worked

But when I sort the x's, it still only gives me the x's and doesnt display there corresponding y points.

You have to specify what you want to print. If you want to print the x's and the y's, then you have to say as much in your print statement.

Originally Posted by itCbitC

perhaps it's time to post the updated code

Code:

#include <stdio.h>

void read_location(double *x, double *y);

int main ()
{
	struct coord{
		double x;
		double y;
	};
	
	struct coord array[20];

	int index=0;
	int choice;
	
	//read in coordinates
	do
	{
		read_location( &array[index].x, &array[index].y);
		index++;
	}while(index < 5);
	
	//test array
	printf("\n");
	printf("%lf", array[3].x);
      
	printf("\n");
	printf("List of entered x's:\n");
	for (index=0; index < 5; index++)
	{
		printf("%4lf\n", array[index].x);
	}

	int pass;
	int a;
	struct coord hold;

	//menu
	do
	{
		printf("Please choose one of the following actions:\n");
		printf("1.) Quit\n");
		printf("2.) Sort by x's:\n");
		printf("3.) Sort by y's:\n");
		printf("4.) Sort by distance:\n");
		printf(":");
		scanf("%d", &choice);
		switch(choice)
		{
			case 1:
				return 0;
			case 2:
				//sort by x
					
					for(pass=1; pass< index; pass++)
					{
						for (a=0; a < index -1; a++)
					{
						if (array[a].x > array[a+1].x)
					{
					        hold=array[a];
						array[a] = array[a+1];
						array[a+1]=hold;
					}
					}
					}

					printf("ordered x's:\n");
					for (a=0; a< index; a++)
					{
					printf("%4lf\n", array[a]);
					
					}

				break;
			case 3:
				//sort by y's;
					for(pass=1; pass< index; pass++)
					{
						for (a=0; a < index -1; a++)
					{
						if (array[a].y > array[a+1].y)
					{
						hold=array[a];
						array[a] = array[a+1];
						array[a+1]=hold;
					}
					}
					}
					
					
					printf("ordered y's:\n");
					for (a=0; a< index; a++)
					{
					printf("%4lf\n", array[a]);
					}
					break;

			case 4:
				//sort by distance
				break;
		}
	}while (choice <=4);

	return 0;
	}

//read in the x and y values
void read_location(double *x, double *y)
{
	printf("Enter x's:\n");
	scanf("%lf", x);
	printf("Enter y's:\n");
	scanf("%lf", y);
}

Originally Posted by tabstop

You have to specify what you want to print. If you want to print the x's and the y's, then you have to say as much in your print statement.

I feel so dumb. I added the y's to the printf statement and everything is showing up as it should.

I can't begin to tell you how much I hate this type of indentation:

Code:

					for(pass=1; pass< index; pass++)
					{
						for (a=0; a < index -1; a++)
					{
						if (array[a].x > array[a+1].x)
					{
					        hold=array[a];
						array[a] = array[a+1];
						array[a+1]=hold;
					}
					}
					}

All the training that a programmer's eye/brain have built up from scanning conventionally indented code, goes right out the window - Poof!

You'll miss a lot of errors if you continue to use it.

Great that it's working - now please indent any future code, with a normal style.

Im wrapping this up and all I have left is sort by distance part. I wrote the code but its not giving me the output Im looking for. It doesnt seem to be doing anything.

Code:

	//sort by distance
					printf("Please enter x:\n");
					scanf("%lf", x2);
					printf("Please enter y:\n");
					scanf("%lf", y2);
					printf("\n");
					printf("List distances:\n");
					for (index =0; index < n; index++)
					{
						
						x3=array[index].x;
						y3=array[index].y;
						cx=(x3-x2)*radian;
						cy= (y3-y2)*radian;
						
						
                                                //test to see y3 and x3 print correct values
					 	printf("%.2lf  %.2lf\n", y3, x3);	
						
						a=sin(cx/2)*sin(cx/2)+cos(x2)*cos(x3)*sin(cy/2)*sin(cy/2);
						
						c=2*atan2(sqrt(a), sqrt(1-a));
						distance=earth*c;
                                                //test a, c, and distance values
                                                printf("%.2lf       %.2lf      %.2lf", a, c, distance);
                                         }

the last printf gives me the values of zero for a, x2 for c, and zero for distance.

What is a supposed to be, and why do you think it's related to distance?

You have one test print statement inside that loop. I suggest adding more of those, to test all your variables, through each step of the loop that you need to, until you find your bug.

Indeed, I like to add a ShowIt() function sometimes, just for that purpose, and then just call that function as needed. Saves a lot of lines of code intruding into my loops.

a and c are used to calculate the distance. Its the formula I found online. Ill take another look and see if I can find the issue.