CISC106, Fall 2006

Second Midterm Exam Makeup (E02b)

Exam Date: November 14, 2006

Name: ________________________________________________________________

UD Email: _____________________________________________@ udel.edu

Circle your section number:

010 011 012 013

014 015 016 017

Do not write your name on any page except this one.

Answer all questions on this paper directly (including the multiple choice)

Total Points: ???

A hint about allocating your time:

You need to answer 100 points worth of questions in 50 minutes, so....

if a question is worth 4 points, it should take 2 minutes or less
if a question is worth 30 points, it should take 15 minutes or less
etc...

Multiple Choice: What is the output?

Each of the problems in this section gives you some input that is typed into MATLAB inside the box with the heavy border.

Which of the boxes afterwards with the light border represents the output you will get back?

Consider each problem as a new problem—that is, suppose that you do a clear command in between each problem.

Feel free to use the blank space on the exam sheet for scratch work. .

(4 pts) Suppose you have the following M file in your current working directory.

function result = mysteryFunction(a,b)
%mysteryFunction does something mysterious
%Examples:
%  ... (omitted to make you think harder)
%D. Duck for CISC106 sect 99, 11/10/2006
  if (a < b)
    result = a:b;
  else
    result = b:a;
  return;
end

Then, suppose you type the following at the MATLAB prompt. What is the output?

>> mysteryFunction(6,3)

```
ans = 
      6:3
>>
```
```
ans = 
      3:6
>> 
```
No output—just a new >> prompt
```
ans =
      3 4 5 6
>>
```
```
ans =
      6 5 4 3
>>
```

(4 pts) Suppose you have the following M file in your current working directory.

function result = yetAnotherFunction(a,b)
%yetAnotherFunction does something with a and b
%Examples:
%  ... (omitted to make you think harder)
%D. Duck for CISC106 sect 99, 11/10/2006
  if (a > b)
    result = [ a b ];
  else
    result = [ b a ];
  end
  return;
end

Then, suppose you type the following at the MATLAB prompt. What is the output?

>> yetAnotherFunction(2,4)

```
ans = 
      8
>>
```
```
ans = 
      24
>> 
```
No output—just a new >> prompt
```
ans =
      2  4
>>
```
```
ans =
      4  2
>> 
```

(4 pts) Suppose you have the following M file in your current working directory.

function result = stillAnotherFunction(v)
%stillAnotherFunction does something with a vector v
%Examples:
%  ... (omitted to make you think harder)
%D. Duck for CISC106 sect 99, 11/10/2006
  result = 0;
  for k=1:length(v)
     result = result + ( v(k)^2 );
  end
  return
end

Then, suppose you type the following at the MATLAB prompt. What is the output?

>> stillAnotherFunction([3 4]);

```
ans = 
      3 4
>>
```
```
ans = 
      7
>> 
```
No output—just a new >> prompt
```
ans =
      9 16
>>
```
```
ans =
      25
>>
```

(4 pts) Suppose you have the same M-file as in the previous question, and you type the following at the MATLAB prompt. What is the output?
```
>> stillAnotherFunction([6 3])
```
1. ```
ans = 
      6 3
>>
```
2. ```
ans = 
      9
>> 
```
3. No output—just a new >> prompt
4. ```
ans =
      36    9
>>
```
5. ```
ans =
      45
>>
```
Basics of C++ programming (short answer)

(4 pts) When writing C++ programs, you need to use a text editor to create the source file. What would you type at the Unix command prompt to bring up the text editor to create or make changes to a C++ file called lab08.cc?
(4 pts) Give the Unix command to compile and run a C++ program called lab08.cc
(4 pts) Give the C++ equivalent of the following MATLAB statement. You do not need a complete C++ program to answer this question—just the line(s) of code that correspond to the one line of MATLAB code listed below.

diameter = input('What is the diameter?');
(4 pts) Give the C++ equivalent of the following MATLAB statement. Assume that the variable result has already been assigned a value (and in the case of C++, it was previously declared as type double.) You do not need a complete C++ program to answer this question—just the line(s) of code that correspond to the one line of MATLAB code listed below.

fprintf('result = %d\n',result);

Fill in the missing code

For each of the questions in this section, you are given
- an M file that defines a function
- an M file which is a acceptance/regression test for that function
- sample output from the regression test
In each problem, there is one or more piece missing that you have to fill in. Fill in the missing piece.

In the file countNegativeNumbers.m, fill in

(7 pts) the missing part of the if statement in the body of the function
(6 pts) the right hand side of an assignment statement

In the file testCountNegativeNumbers.m, fill in

(6 pts) the missing parts of each of the three if tests (i.e. the conditions). Use the examples given in the M file as the test cases.

function result = countNegativeNumbers(vec)
%countNegativeNumbers counts how many even numbers are in a vector
%
%consumes: vec, vector of numbers
%produces: result, a scalar number
%
%Examples:
%   >> countNegativeNumbers([1 -3 0 -5 6])
%   ans = 2
%   >> countNegativeNumbers(-3:1:3)
%   ans = 3
%   >> countNegativeNumbers([1 3 5])
%   ans = 0

  count = 0;

  for k=1:length(vec)    

     if ( vec(k) < 0          )          % <== fill in something here
         count = count + 1;          
     end % end of if
  
  end % end of for

  result = count;                        % <== fill in something here on
                                         %     right hand side

end

% testCountNegativeNumbers.m
% regression/acceptance test for countNegativeNumbers.m
% S. J. Cat, CISC106, sect 99, 11/06/2006


fprintf('Test 1: ');
if (                          )             % <== fill in something here
  fprintf('passed\n');
else
  fprintf('failed\n');
end
 

fprintf('Test 2: ');
if (                           )            % <== fill in something here
  fprintf('passed\n');
else
  fprintf('failed\n');
end
 
fprintf('Test 3: ');
if (                           )             % <== fill in something here
  fprintf('passed\n');
else
  fprintf('failed\n');
end

>> testCountNegativeNumbers
Test 1: passed
Test 2: passed
Test 3: passed
>>

In the file slope.m, fill in

(7 pts) the missing first line of the file. Read the H1 comment and the body carefully, so that you do this exactly right!
(6 pts) one missing line of code in the body of the function

In the file testSlope.m, fill in

(6 pts) the missing parameters to fprintf()

                                                             % <== fill in 
%slope return slope of line passing through two points
%
%consumes: x1, y1, x2, y2: scalar numbers
%produces: theSlope, a scalar number
%
%Examples:
%    >> slope(2,2,4,4)
%    ans = 1
%    >> slope(3,1,5,5)
%    ans = 2
%    >> slope(1,4,1,5)
%    Error: slope is undefined
%    >>
  
denom = x1 - x2;
num = y1 - y2;

if (                )                     % <== fill in this line of code
  error('slope is undefined');
else
  theSlope = num/denom;
  return;
end

% testSlope.m  Peggy Hill for CISC106, sect 99, Arlen Comm. College
% regression/acceptance testing for slope.m
  

fprintf('Test 1: ');
if (slope(2,2,4,4)==1)
  fprintf('passed\n');
else
  fprintf('failed\n');
end

fprintf('Test 2: ');
if (slope(3,1,5,5)==2)
  fprintf('passed\n');
else
  fprintf('failed\n');
end

fprintf('Test 3: ');
try
   x = slope(1,4,1,5);
   fprintf(                  );   % <== fill in some code here
catch
   fprintf(                  );   % <== fill in some code here
end

>> testSlope
Test 1: passed
Test 2: passed
Test 3: passed
>>

Writing an M-file

(30 pts)
In the space below, write a complete M-file to define a function that computes the product of all the elements of a one-dimensional vector of numbers.

Important notes (read these carefully!)
- You do not need to check whether the input is legal or not—for purposes of this exercise, you can assume that you are passed a non-empty, one-dimensional vector of numbers.
- Call your M-file product.m.
- Use steps 1, 2 and 3 of the "design recipe" discussed in lecture.
- Here is an example of the usage of this file. You may use the two examples given here as two of the examples in the comment as part of step 2. Include at least one other example in your comment.
Hints (questions to guide your thinking if you are stuck)
- When accumulating a product, should you initialize to 0 or to 1?
- How do you step through every element in an array?

>> product([3 4 5])

ans =

    60
>> product([-1 -5 -0.5 -1])

ans =

    2.5000

>>

(Extra space in case you need it for the M-file)

(End of Exam)

Notes Sheet for CISC106, E02, Nov 09 2006

MATLAB vs. C++

	MATLAB	C++
comments	`% comment`	`// comment`
string literals	`'delimited with single quotes'`	`"delimited with double quotes"`
variables	don't have to be declared before they are used	have to be declared before they are used (e.g. `int x;`) choices: `double`, `float`, `int`
input	`price = input('please input the price: ');`	`double price; cout << "please input the price: "; cin >> price;`
output	`fprintf('The price is %d\n',price);` or `disp(['The price is ' num2str(price)]);`	`cout << "The price is " << price << endl;`
if/else statements	`if`/`else`/`end` is used to delimit blocks `if (condition) statement; else statement; end`	`{}` is used to delimit blocks; there is no `end` keyword `if (condition) { statement; } else { statement; }`
function definition	start with the word `function` have output variable(s) types are not needed on result or arguments put `end` at the end of function body `function result = nameOfFunction(formalArg1) %nameOfFunction brief statement of purpose %rest of H1 comment statementsInBodyOfFunction; result = someExpression; return; end`	The word `function` does not appear there is no output variable but the output type is required (e.g. `double`) arguments must have types (e.g. `double`) output value follows keyword `return` no keyword end—use `{}` around the body `double nameOfFunction(double formalArg1) { statementsInBodyOfFunction; return someExpression; }`

CISC106, Fall 2006

Second Midterm Exam Makeup (E02b)

Exam Date: November 14, 2006

Multiple Choice: What is the output?

Basics of C++ programming (short answer)

Fill in the missing code

Writing an M-file

Notes Sheet for CISC106, E02, Nov 09 2006

MATLAB vs. C++