call of nonfuncytion in function main()

[anas mashudi]

#include<iostream.h>
#include<fstream.h>
main()
{
char date[15], circle[10], filename[10], filename2[10], ans, write;
int bil,i;
double r[10], area[20], perimeter[15], pow[10];
const double pi=3.1415926535897932384626433832795;
again:
cout<<"\n enter data filename:";
cin>>filename;
// protocol read file
ifstream fp1;
fp1.open(filename);
if(!fp1)
{
cout<<"\n cannot open"<<filename<<"to read";
cout<<"\n continue read file?Y/N";
cin>>ans;
if(ans=='y'||'Y')goto again;
return 0;
}
cout<<"file found";//if file found

//read data
fp1>> date;
fp1>> circle;
fp1>> bil;

for(i=1; i<=bil; i++)
{
fp1>>r[i];
}

//display data on screen
cout<<"\ndate:"<<date;
cout<<"\n\nradius:";

for(i=1; i<=bil; i++)
{
cout<<"\n"<<r[i];
}

fp1.close();

//write to file(lab 6c)

//process
for(i=1; i<=bil; i++)
{
area[i]=pi*(pow(r[i],2));
perimeter[i]=2*(pi*r[i]);
}
//write data to file
cout<<"\nwrite data to file? Y/N";
cin>>write;
if(write=='y'||write=='Y')goto next;
return 0;
next:
cout<<"enter filename output name:";
cin>>filename2;

//protocol write to file
ofstream fp2;
fp2.open(filename2);
if(!fp2)
{
cout<<"\n cannot write to file"<< filename2;
}

fp2<<"\ndate:"<<date;
fp2<<"\n\nradius:"<<"\t\tarea:"<<"\t\tperimeter:";

for(i=1; i<=bil; i++)
{
fp2<<"\n"<<r[i]<<"\t\t\t\t"<<area[i]<<"\t\t\t\t"<<perimeter[i];
}
cout<<"\n file write successfully";
cout<<"\n open file output to read";
fp2.close();
return 0;
}

[weaknessforcats]

At first glance I see an array pow[10].

There is a library function named pow to caculate the power of a number. I expect your array name cannot be pow unless you create a namespace for yourself and put the pow array inside the namespace.

[donbock]

I don't know about C++, but you can't get away with this in C:

if(ans=='y'||'Y')goto again;

You have many opportunities for buffer overflow.

You print an error message if you can't open fp2, but then you fall into the code that writes to fp2.

As weaknessforcats suggests, the real culprit is this line:

area[i]=pi*(pow(r[i],2));

It suggests that "pow" is a function, when you earlier declared pow to be an array of double. Hence you get an error saying that you tried to call a nonfunction.