Playing with C and Ruby

c.c

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

char *monthnames[] = {
        (char*)0, "January", "February", "March", "April", "May", "June",
        "July", "August", "September", "October", "November", "December"
};

int days_in_month[] = { -1, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

struct date {
        int day, month, year;
};

int is_leap_year(struct date *today)
{
        return ((today->year & 3) == 0 && ((today->year % 25) != 0 || (today->year & 15) == 0));
}

void next_day(struct date *today)
{
        bool moving_to_next_month = (today->day == days_in_month[today->month]);
        bool moving_to_next_year  = (moving_to_next_month && (today->month == 12));

        if (moving_to_next_year) {
                today->year++;
                today->month = 1;
                today->day = 1;
                days_in_month[2] = is_leap_year(today) ? 29 : 28;
        }
        else if (moving_to_next_month) {
                today->month++;
                today->day = 1;
        }
        else { /* next day */
                today->day++;
        }
}

int main()
{
        struct date today = { 1, 7, 2017 }; /* start of the financial year */

        for (int i = 1; i <= 365; i++) {
                printf("%d,%d,%s,%d\n", i, today.year, monthnames[today.month], today.day);
                next_day(&today);
        }
        exit(0);
}

r.rb

#!/usr/bin/env ruby

require 'csv'
require 'date'
require 'time'

seconds_in_day = 86400
today = start_time = Time.parse("1 July 2017")

(1..365).each do |day_of_fin_year|
  puts CSV.generate_line([ day_of_fin_year, today.year, Date::MONTHNAMES[today.month], today.day ])
  today = Time.at(start_time + (day_of_fin_year * seconds_in_day))
end

I needed code to generate CSV for each day in the financial year to imported into a spreadsheet. Wrote the Ruby version first and decided to see what the code would look like if written in C. Decided to compare the time that each version took to run, even though the Ruby version runs in less than a second.