bool functions

[vinny1]

For the given input

std::ifstream fin; // 'f'ile in - fin
std::string filename = "fake.txt";
bool isOpen = GetInputFileStream(&fin, filename);
std::cout << filename << " open: ";
std::cout << std::boolalpha << isOpen << std::endl;
std::cout << std::endl;
filename = "real.txt";
isOpen = GetInputFileStream(&fin, filename);
std::cout << filename << " open: ";
std::cout << std::boolalpha << isOpen << std::endl;
std::cout << std::endl;
fin.close();

The output should be

Opening file fake.txt
fake.txt open: false
Opening file real.txt
real.txt open: true

But my bool function returns both as true this is what I have.

bool GetInputFileStream(std::ifstream * fin, std::string filename)
{
fin->open(filename);
std :: cout<< "opening file" << filename << std :: endl;
if(fin)
	return true;
else
	return false;
}

[Peter87]

You are checking if the pointer is null or not.

if(fin == nullptr)

If you want to check the state of the stream you have to dereference the pointer first.

if(*fin)

[vinny1]

The function should be checking whether the file exists or not

when I put (*fin) or (fin==nullptr) it now returns both as false

[JLBorges]

#include <iostream>
#include <string>
#include <fstream>

bool file_exists( std::string path ) // can_open_file_for_input( std::string path )
{ return std::ifstream(path).is_open() ; }

int main()
{
    std::cout << std::boolalpha
              << file_exists( __FILE__ ) << '\n' // true
              << file_exists( "fake.txt" ) << '\n' ; // false
}