Thread: what's the difference?

well...this is the program that i had.....

/* Calculate the total charges and the total hours for the
parking garage. */

#include <iostream>

using std::cout;
using std::cin;
using std::endl;

void calculatecharges (double hoursa, double hoursb, double hoursc);

int main()
{
double a, b, c;

cout<<"Enter the number of hours for CAR 1:";
cin>>a;

cout<<"Enter the number of hours for CAR 2:";
cin>>b;

cout<<"Enter the number of hours for CAR 3:";
cin>>c;

calculatecharges(a, b, c);

return 0;
}

void calculatecharges(double hoursa, double hoursb, double hoursc)
{
double costa = 0;
double costb = 0;
double costc = 0;
double totalhours = 0;
double totalcost = 0;

if(hoursa <= 3)
costa = 2;
else if (hoursa >= 17)
costa = 10;
else
costa = 2 + ((hoursa-3) * .5);

if(hoursb <= 3)
costb = 2;
else if (hoursb >= 17)
costb = 10;
else
costb = 2 + ((hoursa-3) * .5);

if(hoursc <= 3)
costc = 2;
else if (hoursc >= 17)
costc = 10;
else
costc = 2 + ((hoursc-3) * .5);

totalhours = hoursa + hoursb + hoursc;
totalcost = costa + costb + costc;
cout<<"CAR 1 CHARGES: "<<costa<<endl;
cout<<"CAR 2 CHARGES: "<<costb<<endl;
cout<<"CAR 3 CHARGES: "<<costc<<endl;
cout<<"TOTAL: "<<totalhours<< " hours, $"<<totalcost<<endl;
}

and now i'm told that i have to do the same program, but use 3 functions; one to calculate the charges, one to calculate the total hours, and one to calculate the total charges. this time though, i can't use global variables. my question is...what's the difference? doesn't my program fit to the new criteria? also...i still have an error with that function...why? i don't know. it just won't compile without returning an error.

/* Calculate the total charges and the total hours for the
parking garage. */

#include <iostream>

using std::cout;
using std::cin;
using std::endl;

fxn userValues(a, b, c);
fxn calcCharges(double hoursa, double hoursb, double hoursc);
fxn calcTotalHrs(double hoursa, double hoursb, double hoursc);
fxn calcTotalCharges(double hoursa, double hoursb, double hoursc);

int main()
{
userValues a, b, c;

cout<<"Enter the number of hours for CAR 1:";
cin>>a;

cout<<"Enter the number of hours for CAR 2:";
cin>>b;

cout<<"Enter the number of hours for CAR 3:";
cin>>c;

calcCharges(double hoursa, double hoursb, double hoursc);
calcTotalHrs(double hoursa, double hoursb, double hoursc);
calcTotalCharges(double hoursa, double hoursb, double hoursc);

return 0;
}

void calcCharges(double hoursa, double hoursb, double hoursc);
{
double costa = 0;
double costb = 0;
double costc = 0;
double totalhours = 0;

if(hoursa <= 3)
costa = 2;
else if (hoursa >= 17)
costa = 10;
else
costa = 2 + ((hoursa-3) * .5);

if(hoursb <= 3)
costb = 2;
else if (hoursb >= 17)
costb = 10;
else
costb = 2 + ((hoursa-3) * .5);

if(hoursc <= 3)
costc = 2;
else if (hoursc >= 17)
costc = 10;
else
costc = 2 + ((hoursc-3) * .5);
}

void calcTotalHrs(double hoursa, double hoursb, double hoursc);

totalhours = hoursa + hoursb + hoursc;
}

void calcTotalCharges(double hours, double hoursb, double hoursc);
{
double costa = 0;
double costb = 0;
double costc = 0;
double totalcost =0;

if(hoursa <= 3)
costa = 2;
else if (hoursa >= 17)
costa = 10;
else
costa = 2 + ((hoursa-3) * .5);

if(hoursb <= 3)
costb = 2;
else if (hoursb >= 17)
costb = 10;
else
costb = 2 + ((hoursa-3) * .5);

if(hoursc <= 3)
costc = 2;
else if (hoursc >= 17)
costc = 10;
else
costc = 2 + ((hoursc-3) * .5);

totalcost = costa + costb + costc;

cout<<"CAR 1 CHARGES: "<<costa<<endl;
cout<<"CAR 2 CHARGES: "<<costb<<endl;
cout<<"CAR 3 CHARGES: "<<costc<<endl;
cout<<"TOTAL: "<<totalhours<< " hours, $"<<totalcost<<endl;
}

i'm still more confused now than i was before.

In order to use a function the compiler needs to see the function declaration before a function call, just like it needs to see a variable declaration before it can use a variable. Function declarations are usually placed after the list of #includes and before main(). The prototype for a function declaration is:

returnTypeHere functionNameHere(parameterTypesHere);

Note the ; at the end of this line.

Function definitions can be placed either before main() or after mani(), depending on your philosophy. Here is the generic prototype for a function definition:

returnTypeHere functionNameHere(parameterTypeHere parameterNameHere)
{
//function body here
}

Note that the first line of the function definition looks exactly like the function declaration EXCEPT that you HAVE to include the parameter name in the definition (the parameter name is optional in the declaration); AND you DON'T have a semicolon at the end of the line like you do for the declaration.

//Sample program using (silly) function

#include <iostream.h>

//function declaration
void display();

int main()
{
//function call
display();

return 0;
}

//function definition
void display()
{
cout << "Good luck" << endl;
}

return type and parameter type can be any type valid for the program.

You don't need to do prototypes if the function is declared prior to the function that calls it.

ie:

Code:

#include <stdio.h>

int doHello(void)
{
 printf("Hello, world");
 return 0;
}

int main(void)
{
 doHello();
}

OneStiffRod, you can't put them inside another function because the vars will go out of scope.

Oh, nevermind, I see what you were thinking.

huh? lol


scott27349<----newbie