I am trying to extract double values from 2 different text files and will be putting them in arrays. Here is a snippet of the code:
#include <cstdlib>
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
int p;
cout<<"Enter number of ordered pairs: ";
cin>>p;
cout<<endl;
double x[p];
ifstream myfile("x.txt");
while (myfile.good())
{
myfile>>x[p];
cout<<x[p]<<endl;
}
double testx = x[4]+x[3]+x[2]+x[1]+x[0];
cout<<endl<<"The sum of the values of x are: "<<testx<<endl<<endl;
double y[p];
ifstream myfile2("y.txt");
while (myfile2.good())
{
myfile2>>y[p];
cout<<y[p]<<endl;
}
double testy = y[4]+y[3]+y[2]+y[1]+y[0];
cout<<endl<<"The sum of the values of y are: "<<testy<<endl<<endl; system("PAUSE");
return EXIT_SUCCESS;
}
I don't think that the values are being stored properly since checking it via testx
and texty
, the sum of the values are not the expected ones.
You're writing out of bounds of the arrays: you're writing into x[p]
and y[p]
, where x
and y
are arrays of size p
and thus valid indices are from 0
to p-1
.
Not to mention the fact that runtime-sized arrays are not standard C++; some compilers (such as GCC) support them as an extension, but it's best not to rely on them.
When you need a dynamically-sized array in C++, use std::vector
:
int p;
cout<<"Enter number of ordered pairs: ";
cin>>p;
cout<<endl;
std::vector<double> x;
ifstream myfile("x.txt");
double d;
while (myfile >> d)
{
x.push_back(d);
cout<<b.back()<<endl;
}
DTTO for y
.
Note that I changed the loop condition—you were not testing the result of the input operation. More info.
Additionally, if the numbers are arbitrary floating-point values, remember they cannot be simply compared for equality in many situations, due to rounding errors and representation imprecisions.