CS451    Fall 2007    Assignment 1    Due September 6 (in class)
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1.  Define a type called Person, which is a triple, consisting
of the name of a Person, the age of the Person, and the name
of the parent of the Person (assume ever person has just one
parent).

2. Create a list of Persons called plist.  (A global variable)

3.  Write a function called age, which takes a Person, and
returns the age of that Person.

4.  Write a function called name, which takes a Person, and
returns the name of that Person.  

You will need list comprehension for the following functions,
and it is easier if you define a function using previous functions.

5.  Write a function called nameChildren, which takes a Person and
returns a list of the names of all the Children of that person.

6.  Write a function called children, which takes a Person and
returns a list of all the children of that Person.  (You must
return a list of Persons)

7.  Write a function called over21, which takes a Person and
returns a list of all the children of that Person who are over 21
years old.  (Again, return a list of Persons)

8.  Write a function called namesover21, which takes a Person
and returns a list of the names of all the children of that
Person who are over 21 years old.  

9.  Write a function called grandchildren, which takes a Person
and returns a list of the names of all the grandchildren of 
that Person.

For the following, you also need to use recursion.

10. Write a function called descendants, which takes a Person
and returns a list of the names of all the descendants of that Person.