Trailer loops with data sets

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The trailer loop expects a value at the end of the input that is not part of the input.

How is a trailer loop best done when each line of data has more than one number? Let us look at some examples with more than one data number per line.

See the following for more information.

Here is the C code.

#include <stdio.h>

int main() {
	int pos1;
	int len1;
	int value1;
	int value2;
	int value3;
	// trailer loop
	printf("Enter data sets of three numbers or -1 when done.\n");
	printf("\n");
	scanf("%d %d %d",&value1,&value2,&value3);
	pos1 = 0;
	while (value1 >= 0) {
		pos1 += 1;
		printf("%d. Data set %d is: %d %d %d\n",pos1,pos1,value1,value2,value3);
		scanf("%d %d %d",&value1,&value2,&value3);
		}
	len1 = pos1;
	printf("\n");
	printf("Trailer %d found.\n",value1);
	printf("%d data sets found.\n",len1);
	return 0;
	}

Here are some examples of input and output for the above program code.

Here is an example input.

11 22 33
44 55 66
77 88 99

For the above example input, here is the expected output. Here is an example input.

22 33 44
55 66 77

For the above example input, here is the expected output. Here is an example input.

-1

For the above example input, here is the expected output.

Enter data sets of three numbers or -1 when done.


Trailer -1 found.
0 data sets found.

When there is no data to be read, the programming language C will just read empty values, zeros for numbers, without an error.

Some programming languages will raise an error if an attempt is made to read beyond the end of the data.

Here is a way to handle this. Note only one value is input before determining whether the trailer value has been read. Here is the C code.

#include <stdio.h>

int main() {
	int pos1;
	int len1;
	int value1;
	int value2;
	int value3;
	// trailer loop
	printf("Enter data sets of three numbers or -1 when done.\n");
	printf("\n");
	scanf("%d",&value1);
	pos1 = 0;
	while (value1 >= 0) {
		scanf("%d %d",&value2,&value3);
		pos1 += 1;
		printf("%d. Data set %d is: %d %d %d\n",pos1,pos1,value1,value2,value3);
		scanf("%d",&value1);
		}
	len1 = pos1;
	printf("\n");
	printf("Trailer %d found.\n",value1);
	printf("%d data sets found.\n",len1);
	return 0;
	}

Here are some examples of input and output for the above program code.

Here is an example input.

11 22 33
44 55 66
77 88 99

For the above example input, here is the expected output. Here is an example input.

22 33 44
55 66 77

For the above example input, here is the expected output. Here is an example input.

-1

For the above example input, here is the expected output.

Enter data sets of three numbers or -1 when done.


Trailer -1 found.
0 data sets found.