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Write a function (is-older date1 date2) that takes two dates and evaluates to true or false. It evaluates to true if the first argument is a date that comes before the second argument. (If the two dates are the same, the result is false.) Hint: use a let-expression to capture the different pieces of the dates.

Respuesta :

teobguan2019

Answer:

The solution code is written in Python 3

  1. def is_older(date1, date2):
  2.    date1_list = date1.split("/")
  3.    date2_list = date2.split("/")
  5.    for i in range(0, len(date1_list)):
  6.        date1_list[i] = int(date1_list[i])
  7.        date2_list[i] = int(date2_list[i])
  9.    if(date1_list[2] > date2_list[2]):
  10.        return False
  11.    elif(date1_list[2] < date2_list[2]):
  12.        return True
  13.    else:
  14.        if(date1_list[1] > date2_list[1]):
  15.            return False  
  16.        elif(date1_list[1] < date2_list[1]):
  17.            return True
  18.        else:
  19.            if(date1_list[0] >= date2_list[0]):
  20.                return False  
  21.            else:
  22.                return True  
  23.            
  24. print(is_older("2/14/2020", "2/13/2019"))
  25. print(is_older("1/15/2019","1/15/2020"))
  26. print(is_older("3/10/2020", "3/10/2020"))

Explanation:

Let's presume the acceptable date format is (mm/dd/yyyy). We create a function is_older that takes two input dates (Line 1). Next we use split method to convert the two date strings into list of date components, month, day and year (Line 2-3).

The codes in Line 5-7 are to convert each number in the list from string to numerical type.

Next, we do the date comparison started with the year which is indexed by 2. If the year in date1_list is greater than the date2_list, return False (Line 10). If it is smaller, return True (Line 12). If it is equal, then we need to go on to compare the month component  (Line 14 - 17). The comparison logic is similar to checking the year.

If the month of the two dates are the same, we go on to compare the day (Line 19 -22).  If the day in date1_list is greater or equal to the date2_list, it shall return False, else it return True.

We test the function using three sample inputs (Line 24-25) and the output is as follows:

False

True

False

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