Title: More on Mastering Macros.

Make Up Some Points Lost on A3: This is an optional assignment. If you turn it in on time, you may be able to raise your score on Assignment 2. To determine the effect on your A2 score, suppose your A2 score is x percent of the possible points. Then suppose you get y percent of the possible points on this supplement. Your new score on A2 would be z percent, where z = max(x, (x+y)/2). Thus you can make up as many as half the points you missed by successfully completing this supplementary assignment.

Instructions:

• 1. Write a function (code-a-test var exp1 exp2 exp3) that returns a list representing an IF form with a nested IF form that, when evaluated, will cause the value of VAR to be compared to zero, and if it's less than zero, EXP1 is evaluted; if it's equal to zero then EXP2 is evaluated, and if it's positive then EXP3 is evaluated.
• 2. Write a function (code-a-loop n) that returns a list that represents executable Lisp code and that, if executed, causes the first N squares to be printed.
• 3. Write a macro (sign-test var exp1 exp2 exp3) That behaves like CODE-A-TEST, except that: its arguments don't need to be quoted, and the resulting form is evaluated automatically.
• 4. Write a macro (SQUARES-LOOP N) that behaves like (CODE-A-LOOP N), except that the resulting code is evaluated.