CS1321 Fall 2002
Homework 13
Due before 8 a.m. Friday, Oct. 19, 2001
Instructions:
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TURN IN THIS ASSIGNMENT USING WEBWORK!!!
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Do this homework using DrScheme. (Save the file as
a ".scm" file--that is, with a .scm extension.)
- At the top of your file, include the student info portion of the HW Skeleton
(Name, GT Number, HW, Course, Instructor, Lecture Time).
Note:
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Your parameters must be in the same order as they are shown here. If you
are unsure, ask your TA. You will lose credit otherwise.
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Your functions should be named exactly as they are shown in each problem.
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Follow the HW Skeleton, these homeworks will be autograded and must be
in the specified format. You will lose credit otherwise.
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Any submissions which don't execute cleanly (i.e. no errors when you click
Execute) may receive a grade of zero.
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If you do not submit a .scm file, you may
receive a grade of zero.
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Remember that you must be in "Intermediate Scheme".
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For all problems, you should read the words program
and function to mean "program or
group of programs," or "function or group of functions."
Problem 1
Using the dir.ss teachpack from problem 16.3.1,
write a program called dir-depth. It should
consume a directory structure (as created by the dir.ss
function create-dir) and return the depth— the longest path from the highest
level to the lowest level— of the directory is. A directory with no subdirectories
has a depth of 1.
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Fig. 1
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Your program should be called in the following manner:
(dir-depth <directory>)
If dir-depth were to consume the directory
created by dir.ss that represented the
folder "fonts" in Fig. 1, it should return 6. When passed the
directory that represents the folder "cm" in Fig. 1, it should
return 2.
A sample directory is being provided for testing
and examples purposes. Download this sample directory
into an empty fold/directory on your computer and unzip the the provided
zip file. You should see a directory tree that resembles the picture shown
in Fig. 2.
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Fig. 2
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NOTES
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Section
16 of your HtDP book covers various models of directory trees that may
help you better understand this problem.
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Remember to do the analysis for any structures that are provided by the
dir.ss teachpack— there is no need to
provided the define-struct commands given
in the teachpack.
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The help desk in Dr.Scheme can provide you with additional information
on the dir.ss teachpack.
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Exercise 16.3.1 shows how to enter the directory/folder name passed into
the create-dir function in the dir.ss
teachpack. Notice that double backslashes are used on computers running
windows.
Problem 2
Similar to problem
17.3.1, write a function called list-pick.
The function will consume a non-negative integer and a list. The function will
return the nth position element
out of the list, starting from the left most element in position zero of the
list. If the list is too short for there to be an nth
element, your function should return the symbol 'ERROR.
Your function will be called in the following manner:
(list-pick <number> <list>)
NOTES
The use of the list functions length
and list-ref is prohibited. You
will receive a zero for this problem if the length or list-ref functions are used.
Problem 3
Write a function called merge-even that will
consume two list of integers (called list1
and list2 for discussion purposes). The function
will go through list1 and list2
alternately taking even numbers from each of the list. The function will return
a list of even numbers alternating between those found in list1
and list2. The process by which the numbers
are selected are outlined bellow. If one list runs out of numbers before the
other, the remaining numbers of the list which still contains numbers should
continue to be processed.
PROCESS FOR SELECTING NUMBERS
- The first even number from list1 should
be collected first.
- The first even number from list2 should
be collected next.
- Step 1 and 2 should be continued until all the even numbers have been
processed.
Your function will be called in the following manner:
(merge-even <list1> <list2>)
EXAMPLE
>(merge-even (list 1 3 5 6 -1 0 9 10) (list -2
4 8))
(list 6 -2 0 4 10 8)
>(merge-even (list 3 19 21 99 317) (list 11))
empty
NOTES
For this problem the predicate even? may
be used.
(Parts of this assignment were taken from HtDP
Section 14.4, and are the work of Felleisen, Findler, Flatt and Krishnamurthi.
However, modifications have been made by the College of Computing, Georgia Tech;
for educational purposes, for its introductory CS class.)