Learn to Program with C_ Learn to Program using the Popular C Programming Language ( PDFDrive )

Chapter 7 ■ Functions
As written, max returns the larger of two integers. What if we want to find the larger of two
double numbers? Could we use max? Unfortunately, no. If we called max with double values as
arguments, we may get strange results when a double number is assigned to an int parameter.
On the other hand, if we wrote max with double parameters and double return type, it would
work for both double and int arguments, since we can assign an int value to a double parameter
without losing any information.
Note, however, that if we call max with two character arguments, it would work by returning
the larger of the two codes. For example, max('A', 'C') will return 67, the code for C.
Exercise
Write functions to return the smaller of two integers and two floating-point numbers.
7.5 Print the Day
Let us write a program that requests a number from 1 to 7 and prints the name of the day of the
week. For example, if the user enters 5, the program prints Thursday. Program P7.3 does the job
using a series of if...else statements.
Program P7.3
#include <stdio.h>
int main() {
int d;
printf("Enter a day from 1 to 7: ");
scanf("%d", &d);
if (d == 1) printf("Sunday\n");
else if (d == 2) printf("Monday\n");
else if (d == 3) printf("Tuesday\n");
else if (d == 4) printf("Wednesday\n");
else if (d == 5) printf("Thursday\n");
else if (d == 6) printf("Friday\n");
else if (d == 7) printf("Saturday\n");
else printf("Invalid day\n");
}
Now suppose that printing the name of a day of the week was a small part of a much larger
program. We wouldn’t want to clutter up main with this code nor would we want to rewrite this
code every time we needed to print the name of a day. It would be much nicer if we could write
printDay(n) and get the appropriate name printed. We would be able to do this if we write a
function printDay to do the job.
The first thing to ask is what information does printDay need to do its job. The answer is
that it needs the number of the day. This immediately suggests that printDay must be written
with the number of the day as a parameter. Apart from this, the body of the function will contain
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