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Why the use of iostream::eof inside a loop condition considered wrong?
Just because we haven't reached the EOF, doesn't mean the next read will succeed.
Consider you have a file that you read using file streams in C++. When writing a loop to read the file, if you are checking for stream.eof(), you're basically checking if the file has already reached eof.
So you'd write the code like −
Example
#include<iostream>
#include<fstream>
using namespace std;
int main() {
ifstream myFile("myfile.txt");
string x;
while(!myFile.eof()) {
myFile >> x;
// Need to check again if x is valid or eof
if(x) {
// Do something with x
}
}
}Example
While when you use the stream directly in a loop, you'd not be checking the condition twice −
#include<iostream>
#include<fstream>
using namespace std;
int main() {
ifstream myFile("myfile.txt");
string x;
while(myFile >> x) {
// Do something with x
// No checks needed!
}
}
Updated on: 23-Jun-2020
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