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Brian 12-09-2005 06:43 AM

A few function questions
 
I wrote this program to calculate a users gross pay based on marital
status and the number of exemptions they have. I have a few questions
about my functions, heres my code:

#include <iostream>
#include <iomanip>
#include <string>
#include <stdlib.h>
using namespace std;


double federal_taxes(char marital_status, int hours_worked, double
hourly_rate);
double state_taxes(int hours_worked, double hourly_rate);
double gross_pay(int hours_worked, double hourly_rate);
double net_pay(double pay, double federal_tax, double tax);


int main()
{
string first_name;
string last_name;
char marital_status;
int hours_worked;
double hourly_rate;



cout << "Enter your first name: ";
cin >> first_name;
cout << "Enter your last name: ";
cin >> last_name;
cout << "Enter the amount of hours worked: ";
cin >> hours_worked;
cout << "Enter the hourly rate: ";
cin >> hourly_rate;
cout << "Enter your marital status (M) for married (S) for single: ";
cin >> marital_status;


double federal_tax = federal_taxes(marital_status, hours_worked,
hourly_rate);
double tax = state_taxes(hours_worked, hourly_rate);
double pay = gross_pay(hours_worked, hourly_rate);
double total_pay = net_pay(pay, federal_tax, tax);



cout << system("cls");
cout << "Payroll information for ";
cout << last_name;
cout << ", ";
cout << first_name;
cout << ":";
cout << endl;


//HOURS WORKED
cout << "Hours worked:";
cout << fixed;
cout << showpoint;
cout << setprecision(2);
cout << setw(26);
cout << hours_worked;
cout << endl;

//HOURLY RATE
cout << "Hourly rate:";
cout << fixed;
cout << showpoint;
cout << setprecision(2);
cout << setw(27);
cout << hourly_rate;
cout << endl;

//MARITAL STATUS
cout << "Marital status:";
cout << setw(24);
cout << marital_status;
cout << endl;

//NUMBER OF EXEMPTIONS
cout << "Number of exemptions:";
cout << endl;

//GROSS PAY
cout << "Gross pay:";
cout << fixed;
cout << showpoint;
cout << setprecision(2);
cout << setw(29);
cout << pay;
cout << endl;

//FEDERAL TAX
cout << "Federal tax:";
cout << fixed;
cout << showpoint;
cout << setprecision(2);
cout << setw(27);
cout << federal_tax;
cout << endl;

//STATE TAX
cout << "State tax:";
cout << fixed;
cout << showpoint;
cout << setprecision(2);
cout << setw(29);
cout << tax;
cout << endl;

//NET PAY
cout << "Net pay:";
cout << fixed;
cout << showpoint;
cout << setprecision(2);
cout << setw(31);
cout << total_pay;
cout << endl;

}

double federal_taxes(char marital_status, int hours_worked, double
hourly_rate)
{
int num_exemptions;
double federal_tax;


switch(marital_status)
{
case 'M':
cout << "Enter the number of exemptions: ";
cin >> num_exemptions;

if (num_exemptions == 0)
federal_tax = (hours_worked * hourly_rate) * .15;

else if (num_exemptions == 1)
federal_tax = (hours_worked * hourly_rate) * .14;

else if (num_exemptions == 2)
federal_tax = (hours_worked * hourly_rate) * .13;

else if (num_exemptions == 3)
federal_tax = (hours_worked * hourly_rate) * .12;

else if (num_exemptions >= 4)
federal_tax = (hours_worked * hourly_rate) * .11;
break;

case 'S':
cout << "Enter the number of exemptions: ";
cin >> num_exemptions;

if (num_exemptions == 0)
federal_tax = (hours_worked * hourly_rate) * .17;

else if (num_exemptions == 1)
federal_tax = (hours_worked * hourly_rate) * .16;

else if (num_exemptions == 2)
federal_tax = (hours_worked * hourly_rate) * .15;

else if (num_exemptions == 3)
federal_tax = (hours_worked * hourly_rate) *.14;

else if (num_exemptions >= 4)
federal_tax = (hours_worked * hourly_rate) *.13;
break;

}


return (federal_tax);
}

double state_taxes(int hours_worked, double hourly_rate)
{
double tax;
tax = (hours_worked * hourly_rate) * .08;

return tax;
}

double gross_pay(int hours_worked, double hourly_rate)
{
double pay;
pay = hours_worked * hourly_rate;

return pay;
}

double net_pay(double pay, double federal_tax, double tax)
{
double total_pay;
total_pay = (pay - federal_tax) - tax;

return total_pay;
}

First of all, can I get 2 values sent back to main from my
federal_taxes function? I would like to get the value of exemptions
back to main. How would I do it if its possible? Second, I think I want
to create another function for the output. Is there a way to print all
the output in the main function from an output_function?


romain.gaucher@gmail.com 12-09-2005 06:48 AM

Re: A few function questions
 
to return many variables, you cad:

1/ Put theses variables in arguments:
int foo(int value1, int value2, int& return1, int& return2) {}

the "int&" make your variables "writables"...

2/ Return a vector of variables...


Andrew Ward 12-09-2005 07:47 AM

Re: A few function questions
 
Brian wrote:
> First of all, can I get 2 values sent back to main from my
> federal_taxes function? I would like to get the value of exemptions
> back to main. How would I do it if its possible?
>



You could introduce a composite type:

class tax
{
public:
double amount;
int num_exceptions;
tax(double a, int n) : amount(a), num_exceptions(n) {}
};

Then just return this from your function:

return tax(federal_tax, num_exceptions);

Marcus Kwok 12-09-2005 04:54 PM

Re: A few function questions
 
Brian <brian.digipimp@gmail.com> wrote:
> I wrote this program to calculate a users gross pay based on marital
> status and the number of exemptions they have. I have a few questions
> about my functions, heres my code:
>

[code redacted]
>
> First of all, can I get 2 values sent back to main from my
> federal_taxes function? I would like to get the value of exemptions
> back to main. How would I do it if its possible?


Others have already answered this so I will defer.

> Second, I think I want
> to create another function for the output. Is there a way to print all
> the output in the main function from an output_function?


Sure, you could create like

void output_function(const string& first_name,
const string& last_name
/* and the other variables you need */);

in which you have all your cout statements. However, it looks like you
would need to pass in many variables. You could create a struct
containing all the values you need, then just pass the struct to the
output_function. Even better, you could create a class encapsulating
all of the data you want (I'll just call it "Data" to illustrate, but
you will probably want to pick a more meaningful name), and
then provide

ostream& operator<<(ostream& o, const Data& d)
{
cout << d.last_name << ", " << d.first_name << '\n';
/* ... */

return o;
}

Then, you can do like

Data my_data;
// ...
cout << my_data;


By the way, you know you can chain these "<<" statements together?

> //HOURS WORKED
> cout << "Hours worked:";
> cout << fixed;
> cout << showpoint;
> cout << setprecision(2);
> cout << setw(26);
> cout << hours_worked;
> cout << endl;


can be written as

cout << "Hours worked:"
<< fixed << showpoint << setprecision(2) << setw(26)
<< hours_worked
<< endl;

--
Marcus Kwok

Brian 12-09-2005 06:45 PM

Re: A few function questions
 
romain.gaucher@gmail.com wrote:
> to return many variables, you cad:
>
> 1/ Put theses variables in arguments:
> int foo(int value1, int value2, int& return1, int& return2) {}
>
> the "int&" make your variables "writables"...
>
> 2/ Return a vector of variables...


You say the & make your variables "writeables". I thought they made
them refrence points or a pointer?


Default User 12-09-2005 07:00 PM

Re: A few function questions
 
Brian wrote:

> I wrote this program to calculate a users gross pay based on marital
> status and the number of exemptions they have. I have a few questions
> about my functions, heres my code:
>


> double federal_taxes(char marital_status, int hours_worked, double
> hourly_rate)
> {
> int num_exemptions;
> double federal_tax;
>
>
> switch(marital_status)
> {
> case 'M':
> cout << "Enter the number of exemptions: ";
> cin >> num_exemptions;


The question asking for exemptions should be back in main() along with
marital status, then both values passed in. It certainly shouldn't be
repeated in the separate switch cases.

> if (num_exemptions == 0)
> federal_tax = (hours_worked * hourly_rate) * .15;


You should go with a better algorithm, and calculate the tax rate and
pass that in instead of the status.

double CalculateFederalRate(int exemptions, char status)
{
double rate = .11;

if (exemptions < 4)
{
rate += (4 - exemptions) * .01);
}

// status value should be checked before this point!
if (status != 'M')
{
rate += .02;
}

return rate;
}

This isolates the taxrate calculations so that if it changes, it's
contained in one spot, easy to update. Then you remove the whole
switch() from this function, which you've changed to:

double federal_taxes(double federalRate, int hoursWorked, double
hourlyRate)
{
double federalTax;

federalTax = (hoursWorked * hourlyRate) * federalRate;

return federalTax;
}

> First of all, can I get 2 values sent back to main from my
> federal_taxes function? I would like to get the value of exemptions
> back to main. How would I do it if its possible?


Either return a class or struct, or use reference parameters.

> Second, I think I
> want to create another function for the output. Is there a way to
> print all the output in the main function from an output_function?


You have to pass it all over. Your solution really should be using some
sort of OO approach. The basic data should be member variables, with
service functions to do the calculations, and a print one.

You've written essentially a C program with iostream for IO. It should
be rewritten as a C++ program.


Brian

--
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Marcus Kwok 12-09-2005 07:09 PM

Re: A few function questions
 
Brian <brian.digipimp@gmail.com> wrote:
> romain.gaucher@gmail.com wrote:
>> to return many variables, you cad:
>>
>> 1/ Put theses variables in arguments:
>> int foo(int value1, int value2, int& return1, int& return2) {}
>>
>> the "int&" make your variables "writables"...

>
> You say the & make your variables "writeables". I thought they made
> them refrence points or a pointer?


The '&' does indeed make them references. This means that any changes
you make to those variables in the function, also change the original
variable that you passed in, so in that sense it makes them writable.

The parameters without the '&' are passed by value, which means that the
function gets its own local copy of the variables, and the originals are
not changed.


#include <iostream>

void value(int x)
{
x = 5;
}

void reference(int& x)
{
x = 5;
}

int main()
{
int x = 42;
std::cout << "x = " << x << '\n';

std::cout << "calling value()\n";
value(x);
std::cout << "x = " << x << '\n';

std::cout << "calling reference()\n";
reference(x);
std::cout << "x = " << x << '\n';

return 0;
}


--
Marcus Kwok


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