I want to read a line of integers from the user. I'm not sure how to check to see if the input has ended. For example I want to be able to do something like
int x[MAX_SIZE];
int i = 0;
while(cin.hasNext())
{
cin >> x[++i];
}
Example input: 2 1 4 -6
how can I check to see if there's any more for cin to take?
Yo have to do the following
int temp;
vector<int> v;
while(cin>>temp){
v.push_back(temp);
}
also you can check for end of input using
if(cin.eof()){
//end of input reached
}
If cin is still interactive, then there's no notion of "no more input" because it will simply wait for the user to provide more input (unless the user has signaled EOF with Ctrl+D or Ctrl+Z as appropriate). If you want to process a line of data, then get a line from the user (with, say, getline) and then deal with that input (by extracting out of a stringstream or similar).
It is very straightforward. All you need to do is perform the extraction as the condition:
while (i < MAX_SIZE && std::cin >> x[i++])
if the extraction fails for any reason (no more characters left, invalid input, etc.) the loop will terminate and the failure will be represented in the stream state of the input stream.
Considering best practices, you shouldn't be using static C-arrays. You should be using the compile-time container std::array<T, N> (or std::vector<T> if the former is not supported).
Here is an example using std::vector. It also utilizes iterators which does away with having to explicitly create a copy of the input:
std::vector<int> v{ std::istream_iterator<int>{std::cin}, std::istream_iterator<int>{}};
You might want something like this:
int inp;
while(cin >> inp){
....
if(cin.peek() == '\n')
cin.clear(ios::eofbit);
....
}
The while loop runs as long as the I/O is successful. Assuming you want to end input when the line of integers ends, you set the eofbit manually when a \n is encountered. This is checked with the condition if(cin.peek() == '\n'). When the condition is true the while loop terminates. In the example below, I demonstrate how to read a line of integers separated by space into a vector and then print it separated by space
#include<iostream>
#include<vector>
#include<iterator>
#include<algorithm>
using namespace std;
int main(){
vector<int> coll;
int inp;
while(cin >> inp){
if(cin.peek() == '\n')
cin.clear(ios::eofbit);
coll.push_back(inp);
}
copy(
coll.cbegin(),
coll.cend(),
ostream_iterator<int>(cout, " ")
);
cout << endl;
}
using fstream you can do something like this
ifstream ifile("input.txt");
while(!ifile.eof())
{
/* do something */
}
you can also use this
if(!ifile.is_open())
{
/* do something */
}
The idea is silimar with this code below so you can try :
int tmp;
while(cin >> tmp != NULL){ // C++ or while(scanf("%d", &tmp) != -1) {} for C
// do something
}
I usually detect end of cpp stream below:
while (cin.peek() != EOF) {
// To do your stuff...
// NOTE: peek() will set failbit when peeking end of stream and return EOF(-1).
}
