Summary: In this laboratory, you will explore various aspects of the Vector data type that Scheme provides as an alternative to lists.
a. Start DrScheme.
b. Tell DrScheme not to print the lengths of vectors by entering
a. In DrScheme's interaction window, type in a vector literal that denotes a vector containing just the two elements 3.14159 and 2.71828. How does DrScheme display the value of this vector?
b. Create a vector that contains the same two values by using the
c. Create a vector that contains the same two values by using the
a. Tell DrScheme to print the length of vectors by entering
b. Enter each of the following vector expressions in DrScheme; consider the result (perhaps by examining individual elements with
vector-ref); and indicate what vector has been created.
#2(1 2 3 4)
(make-vector 4 0)
c. Tell DrScheme not to print the lengths of vectors and reenter each expression. Do your results differ? What do the differences suggest?
(vector-sum numbers), that takes one argument, a vector of numbers, and returns the sum of the elements of that vector.
You can use
vector->list from the reading as a pattern for
vector-sum -- only a few judicious changes are needed. However, you should not use
vector->list as a helper.
In the reading on vectors, we saw that it was possible to implement
vector->list by using more primitive operations (particularly
Write your own version of
vector-fill!. Remember that
vector-fill! takes two parameters, a vector and a value, and puts that value in every position of the vector.
Consider the following code.
> (define aardvark (list 1 2 3 4)) > (define baboon aardvark) > (define aardvark (cons 5 (cdr aardvark))) > (define chinchilla (vector 1 2 3 4)) > (define dingo chinchilla) > (vector-set! chinchilla 0 5)
a. What do you expect the output of the following commands to be?
> (list-ref aardvark 0) _____ > (list-ref baboon 0) _____
b. Verify your answer experimentally.
c. What do your results suggest about Scheme?
d. What do you expect the output of the following commands to be?
> (list-ref chinchilla 0) _____ > (list-ref dingo 0) _____
e. Verify your answer experimentally.
f. What do your results suggest about Scheme?
Write a procedure,
(rotate! vec) that rotates
the elements in vec. That is,
the initial element of vec at the end, the element at position
1 in position 0, the element at position 2 in position 1, and so on
and so forth.
a. Write a procedure,
that creates a new vector whose elements appear in the reverse order
of the elements in vec.
b. Write a procedure,
that reverses vec
in place. That is, instead of
producing a new vector, it rearranges the elements within vec.
Write a procedure,
(rotate! vec amt), that
rotates the values in vec by amt positions. That is,
the first amt values in vec move to the end, the value
in position amt moves to position 0, the value in position
amt+1 moves to position 1, and so on and so forth.
Just as in the case of
list->vector, you will probably
want to define a helper procedure that fills only part of the vector.
Your termination condition will certainly be different and should probably
involve the length of the vector.
Wednesday, 20 September 2000 [Samuel A. Rebelsky]
Wednesday, 8 November 2000 [Samuel A. Rebelsky]
http://www.cs.grinnell.edu/~stone/courses/scheme/spring-2000/vectors.xhtml(version of April 5, 2000).
Wednesday, 7 February 2001 [Samuel A. Rebelsky]
Thursday, 8 February 2001 [Samuel A. Rebelsky]
vector->listshould be used as a pattern rather than as a helper.
Thursday, 3 October 2002 [Samuel A. Rebelsky]
Thursday, 13 February 2003 [Samuel A. Rebelsky]
Friday, 14 February 2003 [Samuel A. Rebelsky]
Friday, 13 February 2004 [Samuel A. Rebelsky]
I usually create these pages
on the fly, which means that I rarely
proofread them and they may contain bad grammar and incorrect details.
It also means that I tend to update them regularly (see the history for
more details). Feel free to contact me with any suggestions for changes.
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