Ch5 HW1

The purpose of this homework is for you to practice your Lisp program-writing skills. If you find yourself writing “Racket code”, ask for help before the end of the week!

1. (addlength) (SC 3.12) Write a function that takes a list as input and returns a new list with the length of the input added onton the front of it.

    (addlength '(a big cat)) ==> '(3 a big cat)
   

2. (crank-call) (SC 3.14) (a) Without running the function: what is the result of (crank-call 'wanda 'fred)? (b) Modify the function so it behaves as a non-crank call using “quasiquote” but not “list”.

    (defun crank-call (caller callee)
      '(hello callee this is caller calling))
   

3. (SC Section 4.8, EX 4.14) Carefully state the rules for evaluating and and or. What is (and 'a 'b)? What is (or nil 'bank 'money)? Give the results of each without typing them:

       (and ’fee ’fie ’foe)
       (or ’fee ’fie ’foe)
       (or nil ’foe nil)
       (and ’fee ’fie nil)
       (and (equal ’abc ’abc) ’yes)
       (or (equal ’abc ’abc) ’yes)
   

4. (same-sign) (SC, Page 124) Write a function (same-sign a b) that returns true if a and b have the same sign (choices: +,-, or 0).

5. Get the handout and do exercise 6.41 (SC, Ex 6.41). Use the starter code that loads the house definition.