Difference Between Dates Program in Ruby not working - ruby

Question

def getNumDaysInMonth(month, year)
if (month ==1 || month ==3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12 )
return 31
elsif (month == 2)
if (isLeapYear?(year)== true)
return 29
elsif (isLeapYear?(year)== false)
return 28
end
elsif (month == 4 || month == 6 || month == 9 || month ==11 )
return 30
end
end
def isLeapYear?(year)
if (year % 400 ==0)
return true
elsif (year% 100 != 0) and (year%4==0)
return true
else
return false
end
end
def numDaysInYear(year)
days = 365;
if (isLeapYear?(year)== true)
return days +=1
else
return days
end
end
def differenceBetweenDates()
puts "Enter in a starting date: "
startDate = gets
puts "Enter in an ending date: "
endDate = gets
mdyArr = startDate.split("/", 3)
mdyArr2 = endDate.split("/",3)
startMonth = mdyArr[0].to_i
startDay = mdyArr[1].to_i
startYear = mdyArr[2].to_i
endMonth = mdyArr2[0].to_i
endDay = mdyArr2[1].to_i
endYear = mdyArr2[2].to_i
differenceVal = 0
if (startYear < endYear)
daysleftMonth = (getNumDaysInMonth(startMonth,startYear)) - startDay + 1
differenceVal = daysleftMonth
daysleftyear = 0
counter = 1
while counter <= 12
daysleftyear += (getNumDaysInMonth(counter,startYear))
counter += 1
end
differenceVal += daysleftyear
eachYear = 0
counter = startYear + 1
while counter < endYear
eachYear += (numDaysInYear(counter))
end
differenceVal += eachYear
daysleftyear = 0
counter = 1
while counter < endMonth
daysleftyear += (getNumDaysInMonth(counter, endYear))
end
differenceVal += daysleftyear
daysleftendMonth = 0
counter = 1
while counter <= endDay
daysleftendMonth += daysleftendMonth
end
differenceVal += daysleftendMonth
puts differenceVal
end
end
differenceBetweenDates()

Answer 1

First off, let's write Ruby like Ruby and cut your support methods down to a much more manageable bit of code. Remember that the value of the last expression in a method will be the method's return value. This includes conditional expressions like if/else.
def getNumDaysInMonth(month, year)
raise ArgumentError.new("Month mus be between 1 and 12") if month < 1 || month > 12
if [1, 3, 5, 7, 8, 10, 12].include?(month)
31
elsif month == 2
isLeapYear?(year) ? 29 : 28
else
30
end
end
def isLeapYear?(year)
year % 400 == 0 || (year % 100 != 0 && year % 4 == 0)
end
def numDaysInYear(year)
isLeapYear?(year) ? 366 : 365
end
Where you run into problems is this loop:
while counter < endYear
eachYear += numDaysInYear(counter)
end
counter is never updated, so this loop never ends. You have a few more loops like this.
If you fix these, your program will terminate, though the output is incorrect.
You may wish to create a method day_of_year which determines how far a current day is into the year.
def day_of_year(month, day, year)
raise ArgumentError.new("Month must be between 1 and 12") if month < 1 || month > 12
(1...month).map { |m| getNumDaysInMonth(m, year) }.sum + day
end
You can define a method in terms of that one to figure out how many days are left in he current year.
def days_left_in_year(month, day, year)
raise ArgumentError.new("Month must be between 1 and 12") if month < 1 || month > 12
numDaysInYear(year) - day_of_year(month, day, year)
end
These are both nice, simple methods that are easy to understand. The larger problem can them be expressed in terms of them by adding the days left in the year of the start date to the day of year for the end date, plus the sum of the days in any years in between.
def date_diff(startMonth, startDay, startYear, endMonth, endDay, endYear)
days_left_in_year(startMonth, startDay, startYear) +
day_of_year(endMonth, endDay, endYear) +
(startYear + 1 ... endYear).map { |y| numDaysInYear(y) }.sum
end