
arrays and functions
ok, i need help with using arrays with functions, the following code is supposed to calculate the centroid and area of a polygon, but so far i can only get it to calculate squat, any help would be appreciated(yes i do know there are several things wrong but do not know how to correct them)
#include <iostream>
#include <cmath>
#include <iomanip>
using namespace std;
void getxy (double&, double&);
void calccent (double&, double&);
void answer (double&, double&, double&);
int main()
{
double centx, centy, area;
int n;
double x[]= {n};
double y[]= {n};
getxy (x[n],y[n]);
calccent (x[n],y[n]);
answer (centx, centy, area);
system ("PAUSE");
}
void getxy (double& x[n], double& y[n])
{
int n;
double x[]= {n};
double y[]= {n};
cout << "Enter x and y separated by a space: ";
cin >> x[0];
cin >>y[0];
while (x[n+1]!=x[0]  y[n+1]!=y[0])
{
int n;
cout <<"Insert x and y separated by a space: ";
cin >> x[n];
cin >> y[n];
n=0;
n++;
}
}
void calccent (double& centx, double& centy, double& x[n], double& y[n], double& area)
{
int n;
area=((y[n+1]y[n])*(x[n+1]x[n]))/2;
centx=(1/area)*((y[n+1]y[n])/8))*(pow((x[n+1]+x[n]),2))+(pow((x[n+1]x[n]),2))/3;
centy=(1/area)*((x[n+1]x[n])/8))*(pow((y[n+1]+y[n]),2))+(pow((y[n+1]y[n]),2))/3;
}
void answer (double& centx, double& centy, double& area)
{
cout << "These are the centroid coordinates: " << centx << "," << centy;
cout << "\nThis is area of the polygon: " << area << endl;
}

pointing at a couple of things:
#include <iostream>
#include <cmath>
#include <iomanip>
using namespace std;
void getxy (double&, double&);
void calccent (double&, double&);
void answer (double&, double&, double&);
int main()
{
double centx, centy, area;
int n;
double x[]= {n}; //N has no value X has no size. consider double x[10] = {0}
double y[]= {n};
getxy (x[n],y[n]);
calccent (x[n],y[n]);
answer (centx, centy, area);
system ("PAUSE");
}
void getxy (double& x[n], double& y[n]) //arrays are always reference, lose the &
{
int n; //local N overrides the N that was supposedly visible in the header. (??)
Half your troubles are N  you dont give it a value, its scope is hopping around, etc. Take a good look at every use of N to start with.

well then i guess the question i should ask is if using arrays are justified for the particular purpose i have
i want the user(in this case me)to input any double for x and y and when the x and y first input is input again it terminates the loop and then puts all those values in my equations
taking out the n's and the &'s did help alot tho
updated:
#include <iostream>
#include <cmath>
#include <iomanip>
using namespace std;
void getxy (double&, double&);
void calccent (double&, double&);
void answer (double&, double&, double&);
int main()
{
double centx, centy, area;
int n;
double x[]= {n};
double y[]= {n};
getxy (x[n],y[n]);
calccent (x[n],y[n]);
answer (centx, centy, area);
system ("PAUSE");
}
void getxy (double x[], double y[])
{
int n;
cout << "Enter x and y separated by a space: ";
cin >> x[0];
cin >>y[0];
while (x[n+1]!=x[0]  y[n+1]!=y[0])
{
int n;
cout <<"Insert x and y separated by a space: ";
cin >> x[n];
cin >> y[n];
n=0;
n++;
}
}
void calccent (double& centx, double& centy, double x[], double y[], double& area)
{
int n;
area=((y[n+1]y[n])*(x[n+1]x[n]))/2;
centx=(1/area)*((y[n+1]y[n])/8))*(pow((x[n+1]+x[n]),2))+(pow((x[n+1]x[n]),2))/3;
centy=(1/area)*((x[n+1]x[n])/8))*(pow((y[n+1]+y[n]),2))+(pow((y[n+1]y[n]),2))/3;
}
void answer (double& centx, double& centy, double& area)
{
cout << "These are the centroid coordinates: " << centx << "," << centy;
cout << "\nThis is area of the polygon: " << area << endl;
}

I don't arrays are necessary here. Isn't the value calculated after the user has entered a pair of values? In that case, you can stick to a single pair of double, and simply overwrite this pair on each iteration.
If you want to read multiple pairs, use a vector or some other container. This will free you from the burden of declaring the array's size at compiler time and will make your code simpler.
Danny Kalev
Similar Threads

By tenpoints in forum VB Classic
Replies: 4
Last Post: 02142006, 09:11 PM

By aesoprock00 in forum Java
Replies: 2
Last Post: 02122006, 12:17 AM

By peter higgins in forum VB Classic
Replies: 1
Last Post: 02142001, 12:31 PM

Replies: 1
Last Post: 09242000, 02:05 AM

By Brian Leung in forum VB Classic
Replies: 12
Last Post: 06202000, 04:06 PM
Posting Permissions
 You may not post new threads
 You may not post replies
 You may not post attachments
 You may not edit your posts

Forum Rules

Development Centers
 Android Development Center
 Cloud Development Project Center
 HTML5 Development Center
 Windows Mobile Development Center
