Jonas Altrock ew20b126@technikum-wien.at

To overview.

The whole source file u4_date2.c.

/* Compile with `clang -std=c99 -Wall -o u4_date2 u4_date2.c` */
/* Test with `../checkproject u4_date2` */

Include C-libraries for input/output.

#include <stdio.h>
#include <stdlib.h>

Exercise 4: if/switch-Conditions

Read a date in the format yyyy-mm-dd and print it in human readable form.

Detailed exercise

Read a date in the given format. Then print it in the format “day[st/nd/rd/th] of name of month, year”.

You may assume that only a valid date is entered.

Example 1

Input:

2016-08-12

Output:

12th of August, 2016

Example 2

Input:

2015-12-31

Output:

31st of December, 2015

Example 3

Input:

2015-10-03

Output:

3rd of October, 2015

Global declarations

Forward declarations of our own functions. Any function we want to call has to be declared before its use. If the definition for these functions is later in the same file, this is called a forward declaration.

The return type const char * is the type of literal strings with double quotes in our code. These strings are stored somewhere in the read-only section of the binary by the compiler.

const char *day_suffix(int d);
const char *month(int m);

main()

int main() {

Use three integer variables for year, month, day.

    int yyyy, mm, dd;

The scanf format codes can use the same constraints as printf, here we want to read a four-digit year, a two-digit month, and a two-digit day.

    scanf("%04d-%02d-%02d", &yyyy, &mm, &dd);

Print in the format day[st/nd/rd/th] of name of month, year.

%s is the format code for printing a string variable.

    printf("%d%s of %s, %d\n", dd, day_suffix(dd), month(mm), yyyy);

Return code 0 for everything OK.

    return 0;
}

day_suffix()

We know that days in a date can only be between 1 and 31, so we only have to handle a few special cases for the English number suffixes.

const char *day_suffix(int d) {

First

    if (d == 1 || d == 21 || d == 31) return "st";

Second

    if (d == 2 || d == 22) return "nd";

Third

    if (d == 3 || d == 23) return "rd";

N-th

    return "th";
}

month()

Map the month number to the fixed string containing its name.

const char *month(int m) {
    if (m == 1) return "January";
    if (m == 2) return "February";
    if (m == 3) return "March";
    if (m == 4) return "April";
    if (m == 5) return "May";
    if (m == 6) return "June";
    if (m == 7) return "July";
    if (m == 8) return "August";
    if (m == 9) return "September";
    if (m == 10) return "October";
    if (m == 11) return "November";
    if (m == 12) return "December";
    return "invalid month";
}