Vectors

• Exercises
  • Exercise 0: Preparation
  • Exercise 1: Create a Simple Vector
  • Exercise 2: Specifying Vector Length
  • Exercise 3: Summing Vectors
  • Exercise 4: Length of Each Element
  • Exercise 5: Filling Vectors
• Notes
  • Notes on Problem 5: Filling Vectors

Exercises

Exercise 0: Preparation

a. If you have not done so already (or if you've forgotten what it says), please reread the reading on vectors.

b. Start DrScheme.

c. Tell DrScheme not to print the lengths of vectors by entering (print-vector-length #f).

Exercise 1: Create a Simple Vector

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 vector procedure.

c. Create a vector that contains the same two values by using the make-vector and vector-set procedures.

Exercise 2: Specifying Vector Length

a. Tell DrScheme to print the length of vectors by entering (print-vector-length #t).

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. the result

• #4(0)
• #4(1)
• #4(1 2)
• #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?

Exercise 3: Summing Vectors

Write procedure, (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.

Exercise 4: Length of Each Element

Write a Scheme procedure, (length-of-every-element strings, that takes as argument a vector of strings and returns a vector containing the lengths of those strings.

> (length-of-every-element '#("red" "white" "and" "blue"))
#(3 5 3 4)

Exercise 5: Filling Vectors

In the reading on vectors, we saw that it was possible to implement list->vector and vector->list by using more primitive operations (particularly vector-set! and vector-length).

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.

Notes

Notes on Problem 5: Filling Vectors

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.