Calendar: Difference between revisions

{{improve|Ruby|<code>Curses.close_screen</code> has an awful side effect: it writes some escape sequences to stdout, which is awful when one pipes stdout to another program. Should stop using Curses, and instead use shell command <code>tput cols</code>.}}

<code>Date</code> class, from the standard library, knows how many days in a month, and which day is Sunday, for both Julian and Gregorian calendars. This program uses <code>Date</code> class, plus its own assumptions, to create the calendar. This program assumes that every year has 12 months and starts with January 1, and every month fits in 6 weeks starting with Sunday.

# Creates a calendar of _year_. Returns this calendar as a multi-line

# string fit to _columns_.

def cal(year, columns)

# Start at January 1.

#

# Date::ENGLAND marks the switch from Julian calendar to Gregorian

# calendar at 1752 September 14. This removes September 3 to 13 from

# year 1752. (By fortune, it keeps January 1.)

#

date = Date.new(year, 1, 1, Date::ENGLAND)

# Collect calendars of all 12 months.

# Make array of 42 days, starting with Sunday.

# Calculate months per row (mpr).

# 1. Divide columns by 22 columns per month, rounded down. (Pretend

# to have 2 extra columns; last month uses only 20 columns.)

# 2. Decrease mpr if 12 months would fit in the same months per

# column (mpc). For example, if we can fit 5 mpr and 3 mpc, then

# we use 4 mpr and 3 mpc.

mpr = (columns + 2).div 22

mpr = 12.div((12 + mpr - 1).div mpr)

# Use 20 columns per month + 2 spaces between months.

width = mpr * 22 - 2

# Join months into calendar.

rows = ["[Snoopy]".center(width), "#{year}".center(width)]

months.each_slice(mpr) do |slice|

slice[0].each_index do |i|

rows.push(slice.map {|a| a[i]}.join " ")

ARGV.length == 1 or raise "usage: #{$0} year"

# Guess width of terminal device.

# 1. Obey environment variable COLUMNS.

# 2. Try to get columns from Curses library.

# 3. Assume 80 columns.

columns = Integer(ENV["COLUMNS"]) \

rescue (require 'curses'

Curses.close_screen # Measure screen, so Curses.cols != 0.

Curses.cols) \

rescue 80

puts cal(Integer(ARGV[0]), columns)</lang>