 |
|
Program involving classes: [See the Chapter on Classes in the PPG for much of the notation here.] Note that even though this problem also involves dates, it is independent of the date problem in Recitation on Regular Expressions. You should not have any common code between the two problems. This problem has you working with dates and times. Ruby, like most programming languages, has library functions for treating times and dates, and in normal applications, you should use such library functions. This problem has you creating classes from scratch in order to learn how to do it. You are not allowed to use Ruby time/date library classes for this assignment. Consider the following Date1 class in Ruby. (Here is the whole file, Date1 class plus test code: date.rb. I named this class Date1 because Ruby has a library class Date. It actually worked to redefine the library class, but there were other problems.)
| Date1 class in Ruby, file: date.rb | |
|---|---|
| The class Date1 | Test code and a run |
#!/usr/bin/ruby
class Date1
attr_reader :year, :month, :day
def initialize(y, m, d)
if check_date(y, m, d)
@year, @month, @day = y, m, d
else
@year, @month, @day = 2000, 1, 1
end
end
@@mon = [nil,"Jan","Feb","Mar","Apr",
"May","Jun","Jul","Aug",
"Sep","Oct","Nov","Dec"]
@@days = [0, 31, 28, 31, 30, 31, 30,
31, 31, 30, 31, 30, 31]
def check_date(y, m, d)
if m < 1 or m > 12 or
d < 0 or d > 31 or y < 0
false
elsif d > 0 and d <= @@days[m]
true
elsif m == 2 and d == 29 and
is_leap(y)
true
else
false
end
end
def is_leap(y)
if (y%400 == 0 or
(y%4 == 0 and y%100 != 0) )
true
else
false
end
end
def to_s
@@mon[@month] + " " + day.to_s +
", " + year.to_s
end
def incr_day
@day +=1
if not (@month == 2 and
is_leap(@year) and
@day == 29) and
@day > @@days[@month]
@day = 1
incr_month
end
end
def incr_month
@month +=1
if @month > 12
@month = 1
incr_year
end
end
def incr_year
@year += 1
end
end
|
def test_date(y, m, d)
date = Date1.new(y, m, d)
print "Start Date: ", date," "
date.incr_day
print "\n Next day: ", date
date.incr_day
print "\n Next day: ", date
date.incr_day
print "\n Next day: ", date,
"\n"
end
print "TEST ORDINARY DATES\n"
test_date(2004, 4, 22)
test_date(2013, 3, 30)
test_date(2013, 4, 29)
print "\nTEST YEAR END\n"
test_date(2001, 12, 30)
test_date(1999, 12, 30)
print "\nTEST LEAP YEARS\n"
test_date(2004, 2, 28)
test_date(2001, 2, 27)
test_date(2000, 2, 28)
test_date(1900, 2, 27)
test_date(2100, 2, 27) |
- Answer the following questions about the Ruby program above.
(These are not necessarily obvious. You will need to consult the
reference above, or some other reference.)
- In code outside the class (at the top of the right hand column above), the statement on the third line is (truncated) "print date". This statement causes things to be printed. How is the output determined?
- Does the class Date1 have a constructor? What is it?
- What is the meaning (or purpose) of the character '@' in front of year in the code?
- What is the meaning (or purpose) of the characters '@@' in front of days in the code?
- What is the purpose (or effect) of the line attr_reader :year, :month, :day ?
- In the same file add another class Time1 that will keep track of hours, minutes, and seconds. This new class should be similar to the Date1 class. (Again, it is named Time1 because Ruby has a library class named Time.) In particular, it should have methods: initialize, check_time, to_s, incr_sec, incr_min, and incr_hour. Test this new class with code to instantiate time objects and to test incrementing by seconds, including showing that it handles the end of a minute and the end of an hour correctly.
- Change your Time1 class so that it inherits the Date1 class, that is Date1 is a superclass of Time1, and Time1 is a subclass of Date1. (In Java terms, Time1 extends Date1, and in place of the Java "Time1 extends Date1", Ruby writes "Time1 < Date1". The initializer for Time1 should now have 6 parameters, including the ones before, along with year, month, and day. These last three will be passed on into Date1 using the super method. [Again see the Chapter on Classes in the PPG.]
- Alter the incr_hour method of Time1,
so that in case an addition goes past hour 23, it will wrap around
to hour 0 and increment to the next day.
It is permissible to change the code in the class Date1,
although I didn't need to make any changes. There are many different
ways to write this code. You should test your program with the
following initial data, and your output should look something
like the following:
Possible output for this question Start Time: Apr 22, 2004 13:15:30 Next second: Apr 22, 2004 13:15:31 Next second: Apr 22, 2004 13:15:32 Start Time: Feb 28, 2000 13:59:59 Next second: Feb 28, 2000 14:00:00 Next second: Feb 28, 2000 14:00:01 Start Time: Feb 28, 2000 23:59:59 Next second: Feb 29, 2000 00:00:00 Next second: Feb 29, 2000 00:00:01 Start Time: Feb 29, 2000 23:59:59 Next second: Mar 1, 2000 00:00:00 Next second: Mar 1, 2000 00:00:01 Start Time: Feb 28, 2001 23:59:59 Next second: Mar 1, 2001 00:00:00 Next second: Mar 1, 2001 00:00:01 Start Time: Dec 31, 2001 23:59:58 Next second: Dec 31, 2001 23:59:59 Next second: Jan 1, 2002 00:00:00 Start Time: Apr 30, 2001 23:59:58 Next second: Apr 30, 2001 23:59:59 Next second: May 1, 2001 00:00:00
What you should submit:
| Contents of submission for Recitation 14: Last Name, First Name; Course Number; Recitation Number. 1. Give short answers to the questions here. 2. For your own benefit and for partial credit, you should first create the class Time1 as a completely separate class (in a separate file). This is very similar to Date1, but simpler, so you should really try this one. You should test this separately and show your test. 3. and 4. These parts just add extra features. For full credit, it is enough to have a single Ruby program in a single file that does everything, producing roughly the output shown above for the 7 given inputs. (The two classes could also be in separate files, but in that case you would need a "require" statement.) |
Revision date: 2014-04-30. (Please use ISO 8601, the International Standard Date and Time Notation.)