Homework Part 1.
Due next Tuesday, 2/19/19

Recall the definitions of reflexive, symmetric and transitive relations.
Recall, too, that a relation is a set of ordered pairs.
Section 2.5.2 in Makinson (p44) defines the following:
A similarity relation is when a relation is both reflexive and symmetric, but not transitive.
An equivalence relation is when a relation has three properties - transitivity, symmetry and reflexivity.
Unfortunately, Makinson does not define a relation type when a relation is reflexive and 
transitive, but not symmetric. I will call this an "aintbad" relation because, "Two out of three ain't bad."

	(1) Using the 2/12 lab as a starting point, create three functions:
	    similarity?
		equivalence?
		aintbad?
	that will test a binary relation "R" over A, where A = {1, 2, 3} to see if it 
	qualifies as one of these relations. 
	(2) Find a test case that will work for each one of the above three functions. 
	You can have as many tester test cases (that fail any/all three functions) as you like, 
	but you should have one test case that will pass one of the functions above for a total of three.
	
	WHAT TO HAND IN: 
    No need to email a program to me. Print off your definitions file and a copy of your interactions
	file and hand them both in before Tuesday's lecture. 
	A RUBRIC OF SORTS:
	Total of 10 points.
	2 points each for finding a test case that works and includes failing test cases. (6)
	2 points for properly commenting code                                             (2)
	2 points for properly formatting code                                             (2)
	-2 points if you omit your name.