How to write a series of float from text using fstream - c++

Question

Example ABC.txt
10.f 30.2f 20.f
I want to retrieve those information and store inside my array. However i am unsure how to do it.
I dont understand what is
Then (if good), it calls num_get::get (using the stream's selected locale) to perform both the extraction and the parsing operations, adjusting the stream's internal state flags accordingly. Finally, it destroys the sentry object before returning.
std::fstream filestr("ABC.txt", std::fstream::in);
if(!filestr.good()) //Logical error on i/o operation
{
//Unable to process
filestr.close();
return;
}
unsigned index= 0;
unsigned count= 0;
while(filestr.good())
{
float buffer= 0.f;
filestr >> std::skipws >> buffer;
score[index]= buffer;
++index;
}
filestr.close();

Answer 1

There are a number of ways to do this. One way is using stringstreams, in combination with vectors and strings:
#include <fstream>
#include <iostream>
#include <string>
#include <cstdlib>
#include <sstream>
#include <vector>
using namespace std;
int main() {
std::ifstream filestr("C:\\nums.txt", std::fstream::in);
std::vector<double> numbers;
if (!(filestr.good())) {
std::cout << "BAD FILE" << std::endl;
exit(0);
}
else {
std::string temp;
double d = 0.0;
while(std::getline(filestr, temp)) {
std::istringstream iss(temp);
while(std::getline(iss, temp, ' ')) {
std::istringstream ist(temp);
ist >> f;
numbers.push_back(f);
}
}
}
//see that the vector has information in it
for (int i = 0; i < numbers.size(); i++) {
std::cout << numbers[i] << std::endl;
}
filestr.close();
return 0;
}
One thing to note is that you could also use iterators here, but that's something you could implement for yourself.

Answer 2

Super simple with istream_iterator. There is only one tricky bit in the code below. The vector constructor call needs an extra set of parens around the first argument to avoid the Most Vexing Parse.
#include <fstream>
#include <iostream>
#include <iterator>
#include <vector>
#include <algorithm>
using namespace std;
int
main (int argc, char** argv)
{
for (int i = 1; i < argc; ++i) {
ifstream in (argv[i]);
if (!in) {
cerr << "Failed to open " << argv[i] << endl;
continue;
}
vector<double> nums ((istream_iterator<double> (in)), istream_iterator<double> ());
copy (nums.begin (), nums.end (), ostream_iterator<double> (cout, "\n"));
}
return 0;
}