6.001 Recitation – Feb 26, 2003

RI: Konrad Tollmar

• Pop Quiz

0. ‘(say your name)

1. Warm-up

Value Type

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(define (three) 3)

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three

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(three)

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(define four 4)

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four

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(four)

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(+ (three) four)

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(define (add-x x)

(lambda (y) (+ y x)))

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(define add-10 (add-x 10))

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(add-10 5)

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2. Procedures

Given the procedure,

(define apply-to-3-and-4

(lambda (p) (p 3 4)))

What choices for <exp> in a combination of the form (apply-to-3-and-4 <exp>) will cause the following numbers to be returned?

a. --> 7 , <exp> =

b. --> 1 , <exp> =

c. --> 2 , <exp> =

d. --> 3 , <exp> =

e. --> 4 , <exp> =

3. Recursive procedures

Someone, by misstake i guess, redefined the standard + and – procedures (among many other procedures). Write a new recursive add procedures by only using the =, inc and dec procedures.

4. List procedure

Write a process version of a procedure called remove that takes a number and a list and returns a new version of the list where that number is no longer an element.