Create ifstream_iterator error

[Peter_APIIT]

Hello to all, i would like to create ifstream_iterator to use it with file.

#include <iostream>
#include <fstream>
#include <string>
#include <list>
#include <iterator>

using namespace std;


int main()
{
	string dataFile("C:\\Documents and Settings\\nicholas_tse\\Desktop\\.Tc.txt");
	/* Wrong 

	This declare a function taking two parameter
	and return list<int> due to first paremeter
	is ignore and second parameter is pointer
	to function

	Remember 
	1. Parentheses around name is ignore
	2. Parentheses has empty argument is function

	*/

/*
	list<int> inputFile(istream_iterator<int>(dataFile), 
		istream_iterator<int>());
*/
	// Solution 1
/*	list<int> nextInputFile((istream_iterator<int>(dataFile)), 
		istream_iterator<int>());*/

	// Solution 2
	ifstream input(dataFile.c_str());
	istream_iterator<string> start;
	istream_iterator<string> end;
	list<string> strList(start, end);


	// No default constructor available
//	ostreambuf_iterator<int> outBufferIte; 
	istreambuf_iterator<int> inBufferIte;   

	// No default constructor available
//	ostream_iterator<int> outIte; 
	istream_iterator<int> inIte;
	

	return 0;
}

Question

1. Why this is list<int> inputFile(istream_iterator<int>(dataFile),
istream_iterator<int>()); wrong ?
2. Why i try solution 1 there are error list<int> nextInputFile((istream_iterator<int>(dataFile)),
istream_iterator<int>()); ?

error C2440: '<function-style-cast>' : cannot convert from 'std::string' to 'std::istream_iterator<_Ty>'

3. How to create ifstream_iterator to use it with file processing ?

4. Why compiler prohibited me to create ostreambuf_iterator<int> outBufferIte;
ostream_iterator<int> outIte; ?

Thanks.

[Philip Nicoletti]

#1) I'm not sure what your question is. Your code comments state
why it doesn't do what you want.

#2) dataFile is a std::string ... it should be an ifstream

Note concerning your solution # 2 ... it should be

istream_iterator<string> start(input);

#3 and #4 : see example below

#include <iostream>
#include <fstream>
#include <iterator>

using namespace std;

void Create()
{
   ofstream out("ints.txt");
   out << " 1 2 3 4 5 6 7 8 9 10\n";
}


int main()
{
    Create();

    ifstream in("ints.txt");

    istream_iterator<int> inpos(in);
    istream_iterator<int> end_pos;

    ostream_iterator<int> outpos(cout,"\n");

    while (inpos != end_pos)
    {
       *outpos = *inpos;
       ++inpos;
       ++outpos;
    }

    return 0;
}

[PredicateNormative]

Question

1. Why this is list<int> inputFile(istream_iterator<int>(dataFile),
istream_iterator<int>()); wrong ?

Because the compiler will mistake this for a function delcaration for a function called inputFile that returns an object of type list<int> and takes two parameters, the first being a parameter of type istream_iterator<int> called dataFile and the second being a function pointer of no name that takes no parameters and returns an object of type istream_iterator<int>. In order to prevent the compiler mistaking your intended list object declaration as a function declaration, you have to add parenthesis around one or both of the formal parameter declarations. e.g.

list<int> inputFile((istream_iterator<int>(dataFile)), istream_iterator<int>());

list<int> inputFile(istream_iterator<int>(dataFile), (istream_iterator<int>()));

2. Why i try solution 1 there are error list<int> nextInputFile((istream_iterator<int>(dataFile)),
istream_iterator<int>()); ?

error C2440: '<function-style-cast>' : cannot convert from 'std::string' to 'std::istream_iterator<_Ty>'

As Philip has said, your data file is of type std::string, when it should derive from std::istream.

3. How to create ifstream_iterator to use it with file processing ?

Use the code Philip has given you or alternatively the following will do the same thing:

ifstream dataFile("ints.txt");
list<int> inputFile(istream_iterator<int>(dataFile), (istream_iterator<int>()));

[Peter_APIIT]

string nextInputFile((istream_iterator<string>()), 
		(istream_iterator<string>()));

Compiler pops up this error.

error C2440: 'type cast' : cannot convert from 'const std::string' to 'char'

Why this statement cause the error ?

[laserlight]

You are trying to initialise a std::string object named nextInputFile with a pair of input stream iterators that denote a range. These iterators iterate over std::strings. However, the iterators that should be used for the initialisation should iterator over chars. Thus, you get the error saying that the conversion from std::string to char could not be done.

[wydkd]

i think you may need some head files ,i can get through complie with some needed head files
#include <iostream>
#include <fstream>
#include <string>
#include <list>
#include <iterator>
using namespace std;

[PredicateNormative]

string nextInputFile((istream_iterator<string>()), 
        (istream_iterator<string>()));

Compiler pops up this error.

error C2440: 'type cast' : cannot convert from 'const std::string' to 'char'

Why this statement cause the error ?

I expect you probably meant

string nextInputFile(istream_iterator<char>(istreamObj), (istream_iterator<char>()));

where istreamObj is an istream derivative such as fstream, ifstream, stringstream, istringstream etc.

However, if you wanted to put each delimited character sequence (e.g. each word) into a separate element in a container then you could do the following:

vector<string> nextInputFile(istream_iterator<string>(istreamObj), (istream_iterator<string>()));

The above yeilds a vector of strings, where each string element contains a delimited character sequence (e.g. a single word).

[Peter_APIIT]

Thanks.