Functions... 101... for tech dummies... my notes

Trying to get a grasp on functions prior to continuing my attack on the assignment (see my last entry for that temporary hot mess.) Reading my textbook chapter on functions. My notes below...

What is a Function?

A subprogram that can act on data and return a value.

*main() is a function. When your program starts, main() is automatically called and run. There can be multiple functions within main().

*global functions -- functions not part of an object.

*each function has its own name. When that name shows up in the code, the function executes.

***well designed functions perform a single, specific, and easily understood task, identified by the function name.

*built-in functions: part of compiler package
*user-defined functions: defined / written by user (duh)

===================

Return Value: result of work done by a program or function

int MyFunction(); //will return an integer value

int myFunction(int someValue, float someFloat); //will take two values and return an int.

Parameter List: description of values you send into a function (the value/number types, int and variable name, or float and variable name (may be other options but these are all I know so far))

Arguments: values (numbers, etc) passed through a function

int theValueReturned = myFunction (5, 6.7);
myFunction is the function, values 5 and 6.7 are the arguments, and the type of arguments must match the declared parameter type -- (int someValue, float SomeFloat);

====================================

prototype: declaration of a function (calling the function to run within the program)

3 ways to declare a function:

-1 write your prototype into a file and use #include to include it in your program

-2 write the prototype into the file in which your function is used.

-3 define the function before it is called by any other function. The function acts as its own prototype using this method. (But don't do this because it requires functions to be in a particular order which ruins most of the point of using functions in the first place.)

Function prototype: a statement that consists of the function's return type and signature (the name and parameter list for the function)

- if you don't want your function to return a value you can write void in front of it (I don't understand why you'd want to do that, but i find out I'll let you know)

Function definition: function header and body. the header looks like the function prototype except the parameters must be named and no semicolon at the end is used. The body is the set of statements enclosed in braces.
=========================

According to my professor, the proper way to write a function is:

1) write function call
(call for the function you haven't written yet)

2) draw box with parameters and return type

3) write prototype AND comment

4) write the full function definition

========================================

Ok... now I'm going to try to tackle my assignment again now that I understand functions a little more.

Getting Started on my "Functions" Assignment

After class yesterday, I'm still quite confused about functions. So work on this assignment will be challenge.

Before I get into it, a HUGE shout out to my friends Sam & Brian who helped me figure out some of the final bugs in my last program. I got 5/5 on the assignment. (Yeay) -- my professor noted that my indentation was not accurate and I had one redundant note to the program, but she led that slide this time. Phew.

Ok, so this week's assignment, posted in the last entry, is about functions.

I am supposed to write a program that --

1) asks user how much she will put into savings account
2) asks user what the annual interest rate is
3) ask user how long she'll be leaving the money in the savings account
4) tell the user how much money they will have at the end of that period

Ok, sounds simple enough. I could do that WITHOUT functions, but that's not the assignment. So...

My program must define and use a function that performs this calculation.

According to the formula to do that given in class yesterday, I need to...

1) write function call for the function you haven't written yet
2) draw box with the parameters and return types
3) write prototype AND comment for what it's doing
4) write the full function definition

(half of that is still not English to me, so I'm going to take this one step at a time.)

Of course in the assignment, my teacher gave us the prototype (which is supposed to be STEP 3) so... I don't know if that's good or bad. The whole assignment instructions contradicts the professors order of doing this. Eeks.


OK, I'm just going to do this the way she said to in class... because this type of question is apparently going to be on the midterm.

1. Write a function call for the function you haven't written yet

First... what's a function call?

The way to use a function is with a "function call" expression, which consists of the function name followed by a list of "arguments" in parentheses. Another explaination: A function call is an expression containing the function name followed by the function call operator, (). If the function has been defined to receive parameters, the values that are to be sent into the function are listed inside the parentheses of the function call operator. The argument list can contain any number of expressions separated by commas. It can also be empty.

Say What?

Ok. So, what are parameters?

"Parameters provide a simple mechanism for defining and setting the valuesof inputs that are required by a form at startup. Form parameters are variables of type char,number,date that you define at design time." -- GeekInterview

Or, from my class notes: "parameter is a local variable that gets initialized with the function call"

(Still greek to me, but let's move on...) 

ok. So. I think it goes:

functionName (function call operator: list parameters (variables) here)

For this assignment, then, that's...

Well, this is the prototype not the function call, so I'm confused, but anyway...

double futureInvestmentValue (double investmentAmount, double monthlyInternetRate, it years);

More later...

Next week's assignment

What I'll be working on next...

Objectives: Write a reusable C++ function
Write a reusable C++ class
Material from: Day 5, 6; String handouts starting on page 29.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Part 1)
Write a program that asks the user how much she will put into a savings account, what the annual interest rate is, and what period of time she plans to keep the money in the savings account. After these values are read in, report back to the user how much money she will have in her account at the end of the period.

The following formula calculates how an investmentAmount grows when left in a bank account for some years which compounds interest monthly at monthlyInterestRate:
futureInvestmentValue = investmentAmount * (1 + monthlyInterestRate) ^years*12

Your program must define and use a function that performs this calculation.
Here is the prototype, and you must write the comment telling what the function does:

double futureInvestmentValue(double investmentAmount,
double monthlyInterestRate, int years);

Prompts and messages must be in CORRECT ENGLISH. The main() is the only one that reads and prints. There are no cin or cout statements inside the function that returns the futureInvestmentValue().

Plan of Attack
1) Write a function with the following prototype:
double futureInvestmentValue(double investmentAmount,
double monthlyInterestRate, int years);

First thing to do is write a comment for this function.
Before proceeding to step 2, you must have your main() call
futureInvestmentValue(1000, 3.25/100/12, 1)
An annual interest rate of 3.25% is equivalent to a monthlyInterestRate of 3.25/100/12.
The function call above must return 1032.99.

2) Now change only your main() to read values for initial Investment and annual interest rate using cin and cout.
3) Use the following values in the run that you turn into me:
Deposit = 1000, Annual Interest Rate = 4%
4) Be careful of whether your interest rate is monthly, and whether it needs to be divided by 100.


Part 2)
Write a class that can be used to create very short form letters concerning an election. One object represents one form letter, so name your class FormLetter. Each FormLetter object might have different values for these String fields:

• the name of the person the letter is addressed to (to)
• the name of the candidate you want the addressee to vote for (candidate)
• the name of the person the letter is from (from)

If you were to create a new FormLetter object and set the following values for the fields:
to: Hildegard
candidate: The Terminator
from: Brunhilda

And then you were to print that object, your output would look like this:
_____________________________________________

Dear Hildegard,

I would like you to vote for The Terminator
because I think he is best for this state.

Sincerely,
Brunhilda
_____________________________________________

Therefore, class FormLetter needs three member variables: to, candidate, and from.
And class FormLetter needs two member functions: setValues() and printLetter(). Note that the member function called setValues() must have three parameters to accept the new values for the three member variables. The member function printLetter() needs no parameters, because all the data is already inside the object when printLetter() is called.

In order to test this class FormLetter, you must write a main() outside of the class. Every time you write one reusable class, you will always write a main() that will simply declare an object of the reusable class, and call its member functions on the object to see if they work.

So inside main():
1. declare a variable of class FormLetter
2. call setValues() with your chosen values to store inside the object
3. call printLetter() to see if the letter looks right.

In order to receive full credit for this assignment:
• You must go through the above TEST TWICE in the same main(), so that you can see whether the member function setValues() can change the values inside an existing FormLetter object, based on values sent from main().
• This program gets no data from the user's keyboard, all data is included as string literals in the main().

Final Insurance Rate Program

Finished the insurance fee program. I think it's accurate. It's not copy & pasting right but this shows where I fixed the errors I was confused about.

/* This program prints the annual insurance fee for a person based on their car value, age, and number of tickets they have received*/

#include

#include

using namespace std;

int main ()

{

int carValue, age, numberOfTickets;

cout << "Enter your car value: \n";

cin >> carValue;

cout << "Enter your age: \n";

cin >> age;

cout << "How many tickets have you received? \n";

cin >> numberOfTickets;

float baseRate;

baseRate = (carValue*.05);

float ageRate;

if (age<=24)

ageRate=(carValue*.0575);

else if ((age>=25) && (age<=29))

ageRate=(carValue*.055);

else

ageRate=baseRate;

switch (numberOfTickets)

{

case 0: cout << "Your annual insurance rate is " <<>"\n";

break;

case 1: cout << "Your annual insurance rate is " <<>1.10 << "\n";

break;

case 2: cout << "Your annual insurance rate is " <<>1.25 << "\n";

break;

case 3: cout << "Your annual insurance rate is " <<>1.50 << "\n";

break;

default: cout << "Hop on a bike and start peddling. You are so denied.";

}

return 0;

}

/* program output */

Running…

Enter your car value:

10000

Enter your age:

35

How many tickets have you received?

1

Your annual insurance rate is 550

Running…

Enter your car value:

15000

Enter your age:

29

How many tickets have you received?

2

Your annual insurance rate is 1031.25

Running…

Enter your car value:

850

Enter your age:

19

How many tickets have you received?

3

Your annual insurance rate is 73.3125

Running…

12500

Enter your age:

81

How many tickets have you received?

4

Hop on a bike and start peddling. You are so denied.

Building an Insurance Cost Calculator in C++

My assignment this week is to build an insurance rate calculator in C++ using the simplest program possible.

***disclaimer: I am learning C++ and there is a chance that what I have written below is incorrect. I will update with corrections when I get my assignment back.

=================

The assignment variables are as follows:

1) The base rate is 5 percent of the car value

2) If the person is younger than 24, add on 15% of the base rate to the total rate

3) If the person is between 25 and 29, add on 10% of the base rate to the total rate

4) If the person is older than 30, it's just the base rate

5) If the person has 1 ticket, add 10% to the age rate

6) If the person has 2 tickets, add 25% to age rate

7) If the person has 3 tickets, add 50% to age rate (sucks for them)

8) If the person has 4 tickets, deny them coverage (muhahahaha)

Ok, so that's it. Sounds simple, right? Well, maybe it is, but for someone without a programming background, this is tough.

Ok, so our teacher said to break it down piece by piece. Get it working, then simplify.

I'm also supposed to use "Switch," "If," and "Else" which I don't completely understand yet. Hopefully by the end of this post, I will get it.

============

Integer inputs needed to solve problem (cin >>)

Int CarValue

Int Age

Int NumberOfTickets

============

Other Integers

AgeRate

FinalRate

============

Breaking down the math...

BASE RATE

BaseRate=(CarValue*.05)

AGE RATE

If Age is <=24 AgeRate=BaseRate+(BaseRate*.15)

//if age is less than or equal to 24

AgeRate = CarValue*.05+(Car Value *.05 * .15)

AgeRate = Car Value * .05 + Car Value * .0075

AgeRate = Car Value * .0575

If Age is >=25 and <=29 AgeRate=BaseRate+(BaseRate*.10)

//if age is greater than or equal to 25 and less than or equal to 29

AgeRate = CarValue*.05 + (Car Value *.05 *.10)

AgeRate = Car Value * .05 +Car Value *.005

AgeRate = Car Value *.055

FINAL (TICKETS) RATE

If NumberOfTickets = 0

FinalRate = AgeRate

If NumberOfTickets = 1

AgeRate*1.10

If NumberOfTickets = 2

AgeRate*1.25

If NumberOfTickets = 3

AgeRate*1.50

If NumberOfTickets >=4

Denied. Sucka.

=====================

/* Ok, good, I think the math is right there. Now I just have to figure out how to write this program. This is the part where I get really lost. Let's see...*/

===============

Understanding If and Else and the "Logical Operators" (And, Or, Not)

Even though ultimately I want to write this program using Switch, I need to understand If and Else, which is what I'd use if I couldn't simplify with Switch.

//stolen from textbook

"The if statement enables you to test for a condition and branch to different parts of your code, depending on the result. The simplest form:

if (expression)

statement;

The expression in the parentheses can be any expression, but usually contains one of the relational expressions. If the expression has the value false, the statement is skipped. If it's true, it's executed.

if (bigNumber > smallNumber

bigNumber = smallNumber;

So...

{

if (age<=24);

ageRate=(carValue*.0575);

}

{

if ((age=>29) && (age=<24));

ageRate=(carValue*.055);

{

else

ageRate=baseRate;

}

// the logical operators: (And = && ) (Or= ||) ( Not= !)

==============

Let's Switch

Ok, so I'm not sure if I'm supposed to use Switch for just number of tickets, or if I should use it for the ageRate too. Hmm...

First, let me see if I can figure out "Switch."

Stolen from the textbook:

"Unlike if, which evaluates one value, switch statements enable you to branch on to any of several values. The general form of the switch statement is:

switch (expression)

{

case valueOne: statement;

break;

case valueTwo: statement;

break;

default: statement

break;

}

expression is any legal C++ expression, and the statements are any legal C++ statements. If one of the case values matches the expression, program execution jumps to those statements and continues to the end of switch block, unless a break statement is encountered." Also, if nothing matches, it goes to the optional default statement || no default exists and execution falls through switch commands and basically ignores them.

/* Now what's confusing me the most is figuring out where I define what the case is. Also, does it make sense to do Switch for ageRate or is that simple enough that it doesn't need switch? I guess I might be able to make the entire program written in one switch statement, but I'm not sure how I'd do that. Good thing I have all of Sunday afternoon and unlimited blog space to figure this out

Maybe the case name doesn't matter, you just have to label it.

*/

/*ugh*/

/*$*!@*/

/* 30 minutes later. Ok, I'm not getting this. I'm going to try a different approach, starting with the beginning of the program and asking for inputs, then seeing how I can apply switch to them */

#include
using namespace std;
int main(void)

{
int carValue;
cout << "Enter your car value: ";
cin >> carValue;

float baseRate = (carValue*.05)

switch (ageRate)

case

/*huh?*/

/*Google searching "complex switch C++"*/

/*FINALLY figured out what was confusing me... thanks to a devmaster.net thread ... "You can't use ranges in switch statements. Not supported by the language, sorry." Ooooh. So, I can't switch for AgeRate BUT I can for Tickets since that's just a number. OMG. No wonder I was confused. Let's see if this works.*/

#include
using namespace std;
int main(void)

{
int carValue;

int age;

int numberOfTickets

cout << "Enter your car value: ";
cin >> carValue;

cout << "Enter your age: ";

cin >> age;

cout >> "How many tickets have you received?";

cin >> numberOfTickets

float baseRate = (carValue*.05)

{

if (age<=24);

ageRate=(carValue*.0575);

}

{

if ((age=>29) && (age=<24));

ageRate=(carValue*.055);

{

else

ageRate=baseRate;

}

switch (finalRate)

{

case 0: cout >> "Your annual insurance rate is "ageRate<<"\n;

break;

case 1: cout >> "Your annual insurance rate is "ageRate*1.10<<"\n;

break;

case 2:cout >> "Your annual insurance rate is "ageRate*1.25<<"\n;

break;

case 3:cout >> "Your annual insurance rate is "ageRate*1.50<<"\n;

}

{

if numberOfTickets =>4;

cout >> "Hop on a bike. You are so denied.";

}

return 0;

}

/*this is probably incorrect but at the very least I have the start of a program that could feasibly work. Time to move it over to the compiler and see what happens. Holding breath.*/

=========================

If Debugging=Fun cout>>"Liar."

Running program in xcode for error search...

Well, that only had 14 errors and 4 warnings. :) Time to get down to the real work.

#include expects "FILENAME" or

ok, so I copied that top from some blog somewhere. I'm replacing with the top part I used in my last assignment that seemed to work fine.

Down to 12 errors but now at 6 warnings.

Expected initializer before 'cout' for cout << "Enter your care value: ";

I forgot a semicolon...

Now at 11 errors and 7 warnings, huh?

Unused variable: carValue

but I do use it. Or maybe it has to be within the same brackets. Getting rid of the ints I'm defining up top...

10 errors, 4 warnings...

Expected constructor, destructor, or type conversion before '>>' token

Moved the ints to the same place i'm asking for cins and the program seems to like that.

9 errors, 4 warnings...

No match for 'operator>>' in'std::cout>> "How many tickets have you received?"

arrows going wrong way, duh. also adding semicolon I'm missing on next line...

7 errors, 4 warnings

'carValue' was not declared

have a feeling this has to do with brackets

6 errors, 4 warnings...

no, wait... 9 errors, 4 warnings... what???

Expected unqualified-id before '{' token

... down to 4 warnings with the following code:

#include

#include

using namespace std;

int main ()

{

int carValue, age, numberOfTickets;

cout << "Enter your car value: \n";

cin >> carValue;

cout << "Enter your age: \n";

cin >> age;

cout << "How many tickets have you received? \n";

cin >> numberOfTickets;

float baseRate;

baseRate = (carValue*.05);

float ageRate;

if (age<=24)

ageRate=(carValue*.0575);

else if ((age<=24) && (age>=29))

ageRate=(carValue*.055);

else

ageRate=baseRate;

float finalRate

switch (finalRate)

{

case 0: cout << "Your annual insurance rate is ageRate \n";

break;

case 1: cout << "Your annual insurance rate is >> ageRate*1.10 \n";

break;

case 2:cout << "Your annual insurance rate is >> ageRate*1.25 \n";

break;

case 3:cout << "Your annual insurance rate is >> ageRate*1.50 \n";

break;

}

if (numberOfTickets >=4)

cout << "Hop on a bike. You are so denied.";

return 0;

}

================

/*more when i get this figured out*/

Learning C++

I put Javascript on hold and decided to learn C++ first. I'm convinced if I can figure out C++ my brain will understand programming overall and it will make learning other computer languages easier.

I'm taking two courses at the local community college: Intro to C++ and Intro to Data Management Systems. So far I really like the Intro to C++ course, but I'm not quite at the point where I feel comfortable with the language. Granted, I've only had 3 classes as of today. Last week we had to write a BMI calculator from scratch. It took me a while to figure out. She gave us the math formula, but we had to figure out the entire program in our compiler. Once I got the hang of int and float, it made a little more sense.

This week, though, our assignment is harder, and I'm struggling. We're doing Switch and If and Else. Our assignment is to build a insurance rate calculator. There are a bunch of different variables. In my next post, I'm going to work through the code until I figure it out.