C: Record structures with strings

The C programming language has special ways in which to handle strings.

In order to avoid complexity, input that is to be assigned to a string variable, say in a record structure, should be directly read into that string field in the record structure.

Here is an example program.

The example program reads in each line consisting of an integer multiplication factor, a distance, and units for that distance.

The data goes until a trailer value of 0.

There are at most 50 data lines.

All input, processing and output is to be separated.

The input has values for an integer factor, a floating point approximation for a distance, and text for units.

The processing requires a second distance to be calculated.

Thus, the following needs to be in the record structure.

struct Measure {
	int factor1;
	double distance1;
	double distance2;
	char units1[255];
	};

An array with elements that are a record structure are required. There are at most 50 data lines so 50+1 array elements are required since the first list element is 1. To avoid repeating the 50 literal, a constant named MMAX1 is used. The array is called mList1 since it is a measurement list represented as an array. To keep track of the number of data elements actually used, the variable mLen1 is used.

const int MMAX1 = 50;
struct Measure mList1[MMAX1+1];
int mLen1;

To make it easier to process the header loop, the variable factor0 is used.

int factor0;

The standard header loop pattern is used. Note the use of variable factor0 for the possible trailer value.

mLen1 = 0;
// input
scanf("%d",&factor0);
while (factor0 != 0) {
	mLen1 += 1;
	mList1[mLen1].factor1 = factor0;
	scanf("%lf %[^\n]s",&mList1[mLen1].distance1,&mList1[mLen1].units1);
	printf("\t%d. factor %d, distance %3.1lf, units \"%s\"\n",mLen1,mList1[mLen1].factor1,mList1[mLen1].distance1,mList1[mLen1].units1);
	scanf("%d",&factor0);
	}

Important point: In C, the scanf into a string such as units1 should be directly into the record structure.

The processing computes the second distance, distance2 for measurements from 1 to mLen1.

for (int mPos1=1; mPos1 <= mLen1; mPos1++) {
	mList1[mPos1].distance2 = mList1[mPos1].factor1 * mList1[mPos1].distance1;
	printf("\t%d. %d times %0.1lf is %0.1lf %s\n",mPos1,mList1[mPos1].factor1,mList1[mPos1].distance1,mList1[mPos1].distance2,mList1[mPos1].units1);
	}

The output goes though the array and outputs the results for measurements from 1 to mLen1..

for (int mPos1=1; mPos1 <= mLen1; mPos1++) {
	printf("\tMeasure %d is %0.1lf %s\n",mPos1,mList1[mPos1].distance2,mList1[mPos1].units1);
	}

Here is the final program using the above code fragments.

Here is the C code.

#include <stdio.h>

int main() {
	// declarations
	struct Measure {
		int factor1;
		double distance1;
		double distance2;
		char units1[255];
		};
	const int MMAX1 = 50;
	struct Measure mList1[MMAX1+1];
	int mLen1;
	int factor0;
	printf("Input:\n");
	printf("\n");
	mLen1 = 0;
	// input
	scanf("%d",&factor0);
	while (factor0 != 0) {
		mLen1 += 1;
		mList1[mLen1].factor1 = factor0;
		scanf("%lf %[^\n]s",&mList1[mLen1].distance1,&mList1[mLen1].units1);
		printf("\t%d. factor %d, distance %3.1lf, units \"%s\"\n",mLen1,mList1[mLen1].factor1,mList1[mLen1].distance1,mList1[mLen1].units1);
		scanf("%d",&factor0);
		}
	printf("\tFound %d measurements.\n",mLen1);
	// process
	printf("\n");
	printf("Process:\n");
	printf("\n");
	for (int mPos1=1; mPos1 <= mLen1; mPos1++) {
		mList1[mPos1].distance2 = mList1[mPos1].factor1 * mList1[mPos1].distance1;
		printf("\t%d. %d times %0.1lf is %0.1lf %s\n",mPos1,mList1[mPos1].factor1,mList1[mPos1].distance1,mList1[mPos1].distance2,mList1[mPos1].units1);
		}
	// output
	printf("\n");
	printf("Output:\n");
	printf("\n");
	for (int mPos1=1; mPos1 <= mLen1; mPos1++) {
		printf("\tMeasure %d is %0.1lf %s\n",mPos1,mList1[mPos1].distance2,mList1[mPos1].units1);
		}
	return 0;
	}

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

Here is an example input.

2 3.4 miles
3 4.5 inches
4 6.7 centimeters
0

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

Input:

	1. factor 2, distance 3.4, units "miles"
	2. factor 3, distance 4.5, units "inches"
	3. factor 4, distance 6.7, units "centimeters"
	Found 3 measurements.

Process:

	1. 2 times 3.4 is 6.8 miles
	2. 3 times 4.5 is 13.5 inches
	3. 4 times 6.7 is 26.8 centimeters

Output:

	Measure 1 is 6.8 miles
	Measure 2 is 13.5 inches
	Measure 3 is 26.8 centimeters

Here is an example input.

1 1.2 ounces
2 3.4 pounds
0

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

Input:

	1. factor 1, distance 1.2, units "ounces"
	2. factor 2, distance 3.4, units "pounds"
	Found 2 measurements.

Process:

	1. 1 times 1.2 is 1.2 ounces
	2. 2 times 3.4 is 6.8 pounds

Output:

	Measure 1 is 1.2 ounces
	Measure 2 is 6.8 pounds