.Open CSci202 Computer Science II, Session 02, Review
. Previous
.See http://www/dick/cs202/01.html
. Preparation
Study the page below and
chapters 1,2,3, 4,5,6 and write down the questions,
doubts, and surprises that you have on a piece of paper.
.Open Reading
 1 Introduction to Computers, the Internet and
theWorldWideWeb
 2 Introduction to C++ Programming
 3 Introduction to Classes and Objects
 4 Control Statements: Part 1
 5 Control Statements: Part 2
 6 Functions and an Introduction to Recursion
.List
 6.19 Recursion 294
 Example
.See ./02rec.cpp
.See ./20rec.cpp
 6.20 Example Using Recursion: Fibonacci Series 298
 6.21 Recursion vs. Iteration 301
.Close

. Assigned Work Due
Submit one question before 10am by using the web form provided above to
earn credit. This will tell me what topics to cover in the class.

. Exercise
As a member of the CSci Honors committee I have to calculate a special GPA
of all people who apply for honors each qusrter.  This is a GPA of
just the computer science classes -- and the main computer on campus
runs the Student Information System (SIS+) and doesn't do this for me.

So I need to store upto 30 floating point numbers, add them up,
find the maximum and minimum, and print out these three statistics.

Write the Simplest Possible Program that could do this...

. Chapter 3 pages 86 -- Void Functions
I understand that void functions do not return any data, but why is it that some void functions have return (identifier) in them?

The "return" statement has to purposes.  (1) it gets you out of the function.
(2) it can also give the caller a piece of data.

A "void function" may not give the caller any data.  I think it will be
thrown away.

Some void functions have no "return" because there is an implicit,
invisible, "return" placed at the end of the function.

. Chapter 3 pages 88-90 -- CSCI 202
What are arguments and parameters? 

They are the same things.  Mathematicians talk about parameters and
C program talked about arguments.  BUT they both ment the data that is
give to a function to calculate with.  For example
.As_is 		double sin( double x)
(in <cmath>) is a function with a single double parameter called
`x`.  

It is called like this
.As_is 		whatever = a * sin (omega) + b*sin(gamma);
and in each call it is given the `actual` value that to initialize `x`.

. Chapter 3 pages 88-90 -- Functions
How do you define a function's peramiters?

(1) Good spelling is important for wizards.

(2) In the header of the function:
.As_is 	ReturnedType name( parameters )....

. Chapter 3 pages 89-93 -- Classes
Can you give a better explanation on how classes work and what they're used for?

Classes pay off when organizing a complex project -- it splits a thousand
chaotic lines of code into half-a-dozen well organized files with 100
lines of code in each...

A class describes a rules for a collection of similar objects.  An object
contains data value -- named data values, called attributes.  These
are declared in a class.   So, if we needed to talk about Points in a
Cartesian grid we would expect two coordinates called `x` and `y`.  A
class that looks like this:
.As_is 	class Point {
.As_is 		double x;
.As_is 		double y;
.As_is 	...
.As_is 	};
Describes objects with 2 attributes called x and y.   

A class describes data in an object and the functions that
can apply to these objects.

A class also defines rules for constructing new objects.  These
are special functions that have the same name as the class itself:
.As_is 	class Point {
.As_is 		double x;
.As_is 		double y;
.As_is 	  public:
.As_is 		Point(){ x=y=0; }
.As_is 		Point(double x0, double y0){ x=x0; y=y0; }
.As_is 	  ...
.As_is 	};

You can add functions that do things to Points.... for example to
move one.  And you can add functions to calculate properties of
a Point:
.As_is 	  public:
.As_is 		Point(){ x=y=0; }
.As_is 		Point(double x0, double y0){ x=x0; y=y0; }
.As_is 		void move(double dx, double dy){ x+= dx; y+=dy; }
.As_is 		double length(){ return x*x + y*y; }
.As_is 	  ...
.As_is 	};

Object-oriented design is the diffcult task of discovering the best set
of classes to fit the user's needs.

Here are my
.See ./objects.html
rough notes on classes.


. Chapter 3 pages 91 - 95 -- Class member functions
How do you know when you should and shouldn't use the get and set functions?  Are these functions necessary in a Class when you can directly just call the function. (i.e, data()).

Access to the private data in an object must me on a `need to know` basis.

Only add a "get" function when another type of object needs the value.

Only add a "set" function to a class when a different class needs to
change the value.

In a complex program it heps to draw interaction diagrams -- pages 386 thru
to 391 before you write the code.  The arrows tell you the minimum set
of funtions in each class needed to meet the user's needs.

Beware the temptation to add "get" and "set" for every variable
"Just In Case" -- You Ain't Gonna Need It.

. Chapter 3 pages 99-101 -- classes/constructors
what is the difference between a constructor and a Default Constructor?

The Default constructor needs to data and provides suitable
default values for the private data in the newly constructed object.
It is the constructor used for declarations like this
.As_is		Whatever foo;
However, non-default constructors have arguments and are used for declarations
like this:
.As_is		Whatever foo(bar, mumble, 42, 3.14159, "ying tong iddle I po");

. Chapter 4 pages 139 -- BOOL or bool
What is BOOL and when exactly is it used?

The correct spell is
.As_is 		bool
and it is the name of the "Boolean data type" invented by George Boole
to model "The Laws of Thought".     Boolean data have no more than 2
values
.As_is 		false
.As_is 		true

They have a dozen operators:
.As_is 		and	&&
.As_is 		or 	||
.As_is 		not	!
But, the "English" form means the same thing as the older "C" symbolic form.

All tests and conditions become a Boolean value before the if/while/for...
gets to them.

You will use them -- perhaps without knowing it in all interesting programs.

You can also declare `bool` variables:
.As_is 		bool tooBig;
and store values in them for later use:
.As_is 		tooBig = (x >1000000 or y >100000);


. Chapter 4 pages 173 -- boolean
what is boolean attribute?

A boolean attribute is a property of an object that have two values:
true and false.

. Chapter 5 pages 194 -- Essentials of Counter-Controlled Fepetition
which counter-controlled is more usefull when writting a complex code, the FOR repetition statement or the WHILE statement? and what are the benefits of using that statement?

Use counter controled loops for counting and scanning
across data strutcures!  Use the `while` for simple loops.

. Chapter 5 pages 197 -- For Loop
What exactly is a "for loop" and how do you implement them?

It is short hand for a very comoon kind of loop.

.As_is 		for( Student s = class.first(); not s.end(); s.next) ....

The syntax is
.As_is 		for (A; B; C ) D
where A is statement, B is a condition, C an statement and D any
statement.

The compiler converts it into this code
.As_is 		{
.As_is 			A;
.As_is 			while(B)
.As_is 			{
.As_is 				D;
.As_is  			C;
.As_is 			}
.As_is 		}

Using "for" in this saves a lot of typing...

The vast majority of for-loops look like
.As_is 		for( int i =1; i<=n; i++) ....
or
.As_is 		for( int i =0; i<n; i++) ....

. Chapter 5 pages 206-213 -- Case- Swicth
Is there a limit to how many cases in a case switch and can you call a void function into a case switch?

There is no limit to the number of cases in a switch.

THis have nothing to do with calling void-functions.

. Chapter 3 pages 216-217 -- Break and continue statements
What would be a good example of when we would need to use these? Are they used a lot?

IMHO: dont' use "continue".

Use "break" at the end of each "case" in a switch.

Sometimes you may find a "break" helpful in a complex loop.

. Chapter 6 pages 245-305 -- fucntions and vectors
I would like you to explain more about vectors and functions and some examples on how they work or are used.

If we have time.....

. Chapter 6 pages 245 -- recursion
How much more will we talk about and use recursion?

I might give a working recursive function to evaluate in a quiz or
in the final.
Example
.See ./02rec.cpp
.See ./20rec.cpp

The topic does tend to appear in Computer Job interviews.....
See
.See http://en.wikipedia.org/wiki/Recursion
on the wikipedia for an introduction.

Some of the most beautiful structures in Nature (Fractals) are
the result of recursive processes.  See
.See http://en.wikipedia.org/wiki/Fractal
on the wikipedia for more details.

Rule:  Use recursion when the problem has a recursive structure.... the classic
divide-and-conquer algorithms for searching and sorting.
If an important recursive algorithm comes up we will mention it.
We will test half a dozen in one of the labs.

Second fact: when you call a function it gets a new set of variables to play
with and if you don't allow for this then you won't be able to figure out what it does.

Key fact:  recursion works  -- but like all programming 
-- it needs thought, to work well.

. Chapter 6 pages 245-332 -- pass-by-reference
There is quite a bit of information that wasn't gone over in this chapter 
from my last class but in particular I was wondering if you could elaborate
on the functionality and implementation of the idea of passing-by-reference
and passing-by-value?

Pass by value:  the actual parameter is an expression.  It is evaluated before
the function is called.  The result (the value) is passed to the formal
parameter as its initial value.

Pass by reference: The actual parameter must be a variable.
The actual parameter must be a variable.
The actual parameter must be a variable.  Its address is passed to the
function. All operations on the formal parameter are doene to actual
parameter.
(scary!)(but fast).

. Also I was wondering what is Function Overloading?
When two functions have the same name but different typ[es of parameter.

. Chapter 6 pages 255 -- function prototypes and argument coercion
I would like to know what the purpose of a void function prototype is.  Why do we need it and what does it do?

Void functions do things for use.  non-void functions give us values.

. Chapter 6 pages 258-259 -- Rand()
What, if anything, happens if you put an argument into the function rand()? meaning you enter something between the parentheses.

I don't know.

(rule1): Read the Famous Manual
(rule2): Try it and see.

. Chapter 6 pages 279 -- Inline Functions
When is it better to use an inline function?

When it is short.  Ideally one line long.
.As_is 		int min(int a, int b) { return (a<b ? a: a); }

. Chapter 6 pages 281 -- pass by reference
When using '&' for pass by reference, what are the effects of the const 
keyword.  What limitations does it place on the handling of the variable?

When you pass a parameter by reference you normally give permission for the
function to do things to the actual parameter.  It can assign a
new value, it can apply and operator like "++", it can send it
a message:
.As_is 		formalParameter.message(data);
that might change it in some way.

If you add the "const" then the function can not assign a new value
or apply an operation to it.  The only message that it can sent are
those that are also declared const.  And the compiler will check to see if
these message will do things to their object or not.

. Chapter 6 pages 294-298 -- Recursion
In a recursion step, other than incorrectly writing the recursion step, 
would their be a situation where the function does infinite recursion where
it can't break down a problem to a base case

Yes.  Bad designs tend to generate infinite processes -- whether they
are recursive or iterative.

. Chapter 6 pages 302 -- recursion
When is it better to use recursion vs iteration type repetition?

When the problem is recursive then you'd be wise to code it using recursion.
Example:  searching fo something what you can divide up the possibilities
into two nearly equal pieces and can pick the right half to search:

Find_something_in(Here)
.(
	Divide Here into Part1 and Part2;
	Pick Part that contains the target;
	Find_something_in(Part)
.)

But an iterative problem..... I have one hundred random numbers.... add them
up is probably best done with an iteration.

. Chapter 6 pages 294 -- recursion
Is recursion truly nesscary to be able to code at a high level?

Its another tool that a competent programmer uses when needed.

It is also a useful way of thought to have available when solving problems:
If I could solve this subproblem then....

. Chapter 6 pages 281-285 -- References and Reference Parameters
Can you explain what pass-by-reference does and what it means?
. Chapter number pages ppp-ppp -- Reading question
Message
When using an array are you able to make it into a function then call it as an if statement ??

. Chapter 6.21 pages 301 -- iomanip?
What does this allow:
.As_is #include <iomanip>
.See ./iomanip.html


. Chapter 8 pages 414 -- Passing Arguments to functions by reference with pointers
In the book it claims that there are three ways in c++ to pass arguments to a function 1. pass by reference with reference arguments, pass by reference with pointer arguments, as well as pass by value...is their any other more complicated way to pass an argument to a function?

. Lab
Review:
.See http://www/dick/cs202/lab01.html
. Next -- Arrays + Vectors + Project
Topics:
.See http://www/dick/cs202/03.html

The first project
.See ./p1.html
is due in the fourth class.  It is on Arrays
(Chapter 7).  Select one and start it as soon as you can.
Hand in what ever you've got, however bad, at the start of the 4th class.
.Close CSci202 Computer Science II, Session 02, Review
FAQ::="Frequently Asked Questions", see
.See http://www.faqs.org/faqs/
for more FAQ.