Assignment 2 “On Strings and Pointers”

NWEN 241 Assignment 2
“On Strings and Pointers”

In this assignment, you will be given 11 tasks where you will apply your
knowledge about strings and pointers.
The assignment is divided into 3 parts. In Part I (Tasks 1–5), you will be
asked to answer questions about pointers. In Part II (Tasks 6–8) and Part
III (Tasks 9–11), you continue the implementation several basic text editor
operations. You will implement some of the operations in pure C (Part II),
and some in C++ (Part III).
You only need to submit the required implementations. You do not need to
write a main() function, but you would need one if you want to test your
code. Sample code showing an example on how you can test your code
are provided under the files directory in the archive that contains this
file.
Full marks is 100.
Instructions and Submission Guidelines:
• For Parts II and III, you should provide appropriate comments to
make your source code readable. If your code does not work and
there are no comments, you may lose all the marks. See the marking
criteria at the end of this document for details about the marks for
commenting.
• For Parts II and III, you should follow a consistent coding style when
writing your source code. There is a short discussion about coding
style below. See the marking criteria at the end of this document for
details about the marks for coding style.
• Submit the required files to the Assessment System (https://apps.
ecs.vuw.ac.nz/submit/NWEN241/Programming_Assignment_
2) on or before the submission deadline.
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NWEN 241 2019-T1 “On Strings and Pointers” Assignment 2
• Late submissions (up to 48 hours from the submission deadline) will
be accepted but will be penalized. No submissions will be accepted
48 hours after the submission deadline.
Coding Style for Parts II and III
Coding style (also known as coding standard) refers to the use of appropriate indentation, proper placement of braces, proper formatting of control
constructs, etc. Following a particular coding style consistently will make
your source code more readable.
There are many coding standards available (search "C/C++ coding style").
Most of these standards are dense and will take you many days (even
weeks) to read and understand. If you want to follow a lightweight coding style, consult the Linux kernel coding style (https://www.kernel.
org/doc/html/v4.10/process/coding-style.html). You only need
to read sections 1–3 of this document.
Note that you do not have to follow every recommendation you can find
in a coding style document. If you change, for instance the tab size from 8
to 4, that is fine. You just have to apply that style consistently.
Part I: Pointer Concepts
This part will test your conceptual knowledge of pointers. Your answers
should be submitted in a plain text file named part1.txt.
Task 1.
Basics [10 Marks]
1. (2 Marks) Declare a pointer to a floating-point quantity.
2. (2 Marks) Declare a prototype for a function func1 that accepts two
integer arguments and returns a pointer to a long integer.
3. (2 Marks) Declare a prototype for a function func2 that accepts a
character pointer argument and returns a pointer to a character. The
function must not allow the modification of the input argument.
4. (2 Marks) Declare a one-dimensional array of integer pointers with
20 elements.
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NWEN 241 2019-T1 “On Strings and Pointers” Assignment 2
5. (2 Marks) Declare an array of C strings whose initial values are "cyan",
"magenta", "yellow", and "black".
Task 2.
Completion [5 Marks]
A C/C++ program contains the following statements:
1 char u, v = 'A';
2 char *pu, *pv = &v;
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4 *pv = v + 1;
5 u= *pv + 1;
6 pu = &u;
Each character occupies 1 byte of memory. If the value assigned to u is
stored in (decimal) address 1100 and the value assigned to v is stored in
(decimal) address 1101, then
1. (1 Mark) What is the numeric value of the expression &u?
2. (1 Mark) What is the numeric value of the expression &v?
3. (1 Mark) What value is assigned to pv after the completion of line 2?
4. (1 Mark) What is the numeric value of the expression *pv after the
completion of line 4?
5. (1 Mark) What value is assigned to u after the completion of line 5?
Task 3.
Completion [5 Marks]
Consider the following C++ code snippet:
int int1 = 26;
int int2 = 45;
int *int1Ptr = &int1;
int *int2Ptr = &int2;
*int1Ptr = 89;
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NWEN 241 2019-T1 “On Strings and Pointers” Assignment 2
*int2Ptr = 62;
int1Ptr = int2Ptr;
*int1Ptr = 80;
int1 = 57;
std::cout << int1 << " " << int2 << endl;
std::cout << *int1Ptr << " " << *int2Ptr << endl;
1. (1 Mark) What is its output?
2. (4 Marks Explain individually the printed values.
Task 4.
Challenge [3 Marks]
A C/C++ program has the following statements:
short a[] = {1, 2, 4, 8, 16, 32};
short *pa = a;
short **ppa = &pa;
Suppose each short integer quantity occupies 2 bytes of memory. If the
array a is at (decimal) address 1102, pa is at (decimal) address 1114, and
ppa is at (decimal) address 1118, then
1. (1 Mark) What is the numeric value of the expression a?
2. (1 Mark) What is the numeric value of the expression ppa?
3. (1 Mark) What is the numeric value of the expression *ppa + 2?
Task 5.
Challenge [2 Marks]
Consider the following C++ code snippet:
std::string seasons[4] = {"Winter", "Spring", "Summer",
"Fall"};
std::string *strPtr;
strPtr = new string[5];
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NWEN 241 2019-T1 “On Strings and Pointers” Assignment 2
for (int i = 0; i < 4; i++)
strPtr[i] = seasons[i];
1. (1 Mark) Write a C++ code snippet that outputs the contents of the
array to which strPtr points using pointer notation.
2. (1 Mark) Write a C++ code snippet that deallocates the memory space
occupied by the array to which strPtr points.
Part II: Pure C Programming
You may only use the Standard C Library to perform the tasks in this part.
Task 6.
Basics [15 Marks]
In this task, you will create a C header that will declare the functions that
you will implement in Tasks 7 and 8. You may declare constants and userdefines types needed by your function implementations.
Save the header file as editor2.h.
Task 7.
Completion [15 Marks]
In this task, you will implement a function that counts the number of lines
from a given editing buffer. The editing buffer is an array of characters,
and is passed to the function using pointer notation. The size of the buffer
should also be passed to the function. The function will not modify the
contents of the buffer, and this should be indicated in the function header
(and prototype).
The function should be named editor_count_lines. It must return the
number of lines in the buffer. A line is defined as consisting of the characters: (i) from the start of the buffer until a newline character; or (ii) immediately after a newline character until another newline character.
The arguments should be ordered as follows:
1. Editing buffer
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NWEN 241 2019-T1 “On Strings and Pointers” Assignment 2
2. Size of editing buffer
In implementing the function, you must use pointer notation in traversing
the buffer.
Save the function implementation in editor2.c. You may implement
other functions (needed by your implementation) in editor2.c.
Task 8.
Challenge [7.5 Marks]
In this task, you will implement a function that will search for multiple occurrences of a given search string from a given editing buffer. The search
string is a null-terminated array of characters, and is passed to the functions using pointer notation. The editing buffer is an array of characters,
and is passed to the function using pointer notation. The size of the buffer
should also be passed to the function. The function will not modify the
search string and contents of the buffer, and this should be indicated in the
function header (and prototype).
Two other arguments are passed to the function: an array of integers (passed
using pointer notation) and the size of the integer array. This array will be
used for storing the positions of the found occurrences of search string in
the buffer. Position refers to the index of the first letter of the search string
in the buffer.
To clarify the use of the integer array, suppose that the search string is found
at positions 10, 24, 56, and 100, then the values of integer array elements at
indices 0, 1, 2, and 3 should be 10, 24, 56, and 100, respectively. Note that
the function will only be able to search at most K occurrences, where K is
the size of the integer array.
The function should be named editor_search_multiple. It must return the number of elements in the integer array which has valid positions.
In the example above where the search string is found at positions 10, 24,
56, and 100, the function must return 4.
The arguments should be ordered as follows:
1. Editing buffer
2. Size of editing buffer
3. String to be searched
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NWEN 241 2019-T1 “On Strings and Pointers” Assignment 2
4. Integer array
5. Size of integer array
In implementing the function, you must use pointer notation in traversing
the search string, buffer and integer array.
Save the function implementation in editor2.c. You may implement
other functions (needed by your implementation) in editor2.c.
Part III: C++ Programming
You may use the C++ Standard Library to perform the tasks in this part.
Task 9.
Basics [15 Marks]
In this task, you will create a C++ header file that will contain declaration
of a class for implementing Tasks 10 and 11. You may declare constants and
user-defines types needed by your implementations.
The class should be named EditorUtilities and should be defined
within editor2 namespace.
Save the header file as editor2.hh.
Task 10.
Completion [15 Marks]
In this task, you will implement a member function of EditorUtilities
for counting the number of words in a given editing buffer. The member function should be public and callable even without the instance of
EditorUtilities.
The editing buffer is an array of characters, and is passed to the function
using pointer notation. The size of the buffer should also be passed to the
function. The function will not modify the contents of the buffer, and this
should be indicated in the member function header (and prototype).
The function should be named countWords. It must return the number
of words in the buffer. A word is defined as consisting of non-whitespace
characters. Words are separated by whitespace charaters. In C/C++, the
whitespace characters include:
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NWEN 241 2019-T1 “On Strings and Pointers” Assignment 2
• Space: ' '
• Horizontal tab: '\t'
• Newline: '\n'
• Vertical tab: '\v'
• Form feed: '\f'
• Carriage return: '\r'
The arguments should be ordered as follows:
1. Editing buffer
2. Size of editing buffer
In implementing the function, you must use pointer notation in traversing
the buffer.
Save the implementation in editor2.cc. You may implement other member functions (needed by your implementation) in editor2.cc.
Task 11.
Challenge [7.5 Marks]
In this task, you will implement a member function of EditorUtilities
that will search for multiple occurrences of a given search string from a
given editing buffer, ignoring case. The member function should be public
and callable even without the instance of EditorUtilities.
This is a variation of Task 6, hence, all the points in that task applies to this
as well, except for the following:
• When searching for the occurrence of search string, case should be ignored. This means that if the search string is "Hello", then "Hello",
"hello", "heLLo", etc. are considered as occurrences.
• The search string argument is of type std::string, not an array of
characters.
• The member function should be named searchMultipleNoCase.
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NWEN 241 2019-T1 “On Strings and Pointers” Assignment 2
In implementing the function, you must use pointer notation in traversing
the search string, buffer and integer array.
Save the implementation in editor2.cc. You may implement other member functions (needed by your implementation) in editor2.cc.
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NWEN 241 2019-T1 “On Strings and Pointers” Assignment 2
Marking Criteria for Tasks 7, 8, 9, and 11:
Criteria Weight Expectations for Full Marks
“Compilability” 10% Source code compiles without warnings
Commenting 10% Source code contains sufficient and appropriate
comments
Coding Style 10% Source code is formatted, readable and uses a
coding style consistently
Use of Pointers 30% Uses pointers correctly and as specified
Correctness 40% Handles all possible cases correctly
100%
Marking Criteria for Tasks 6 and 9:
Criteria Weight Expectations for Full Marks
Commenting 10% Source code contains sufficient and appropriate
comments
Coding Style 10% Source code is formatted, readable and uses a
coding style consistently
Correctness 40% Addresses all specifications and correctly uses
syntax in the declarations and/or definitions
Completeness 30% Declaration and/or definition of all required
functions (in Task 6) and class and member
functions (in Task 9)
100%
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