how to pass an ifstream object to a function

This is a discussion on how to pass an ifstream object to a function within the C++ Programming forums, part of the General Programming Boards category; hi masters!! can anyone plese help me in this? i want to pass an ifstream object to function. please dont ...

  1. #1
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    how to pass an ifstream object to a function

    hi masters!!

    can anyone plese help me in this?
    i want to pass an ifstream object to function.

    please dont suggest me to use istream instead!!!!!!!

    i know it can b passed by reference, but i am not been able to do that!!

    my code
    Code:
    #pragma warning(disable:4786)
    #pragma warning(disable:4996)
    
    #include <vector>
    #include "common.h"
    #include "defFile.h"
    #include<uf.h>
    #include <iostream>
    #include <uf_part.h>
    #include <uf_curve.h>
    #include"runner_blade.h"
    
    using namespace std;
    void defFile::readFile(char *DefFileName)
    { 
    	char buf[256];
    	int i=0,j=0;
    	ifstream inpfile;
    	inpfile.open(DefFileName);
    	while(!inpfile.eof())
    	{
    		inpfile.getline(buf,256,'\n');
    		if(strstr(buf,"action"))
    		{
    			//I'm check whether the string action is coming or not		
    			inpfile.getline(buf,256,'\n');		
    			sscanf(buf,"%d %d",&ActionSide.NumberOfSections,&ActionSide.NumberOfPoints);
    			readLine(ActionSide.NumberOfSections,ActionSide.NumberOfPoints,ifstream &inpfile);			
    		}
    	}
    	inpfile.close();
    }





    error:


    1>d:\backup_qi-287\geconfidential\rajesh\hitachi_runner_blade\cod e_runner_blade\runner_blde\runner_blde\deffile.cpp (28) : error C2275: 'std::ifstream' : illegal use of this type as an expression

  2. #2
    C++ Witch laserlight's Avatar
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    It sounds like you need to #include <fstream>

    please dont suggest me to use istream instead!
    If I suggest using an ifstream, I'm suggesting to use an istream, since an ifstream is an istream.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  3. #3
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    thanks for suggestion but still its not working & i think u misunderstood me ! i want to use "ifstream " . i dont want to use "istream"!

  4. #4
    C++ Witch laserlight's Avatar
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    thanks for suggestion but still its not working
    Ah, but what is the error message now? I suspect it has changed, because the next problem you have appears to be here:
    Code:
    readLine(ActionSide.NumberOfSections,ActionSide.NumberOfPoints,ifstream &inpfile);
    If readLine() takes an ifstream (or istream, for that matter) by reference, you would write:
    Code:
    readLine(ActionSide.NumberOfSections, ActionSide.NumberOfPoints, inpfile);
    i think u misunderstood me ! i want to use "ifstream " . i dont want to use "istream"!
    I understand you very well. You, on the other hand, do not understand that there is an is-a relationship between ifstream and istream, and consequently you should prefer to use reference to istream parameters unless ifstream specific functionality is to be used.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  5. #5
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    hi expert!! i have done whatever u said & i am getting this error!! u have to b very patient with me, because i am begineer!!!

    thanks!!



    error C2248: 'std::basic_ios<_Elem,_Traits>::basic_ios' : cannot access private member declared in class 'std::basic_ios<_Elem,_Traits>'

  6. #6
    C++ Witch laserlight's Avatar
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    error C2248: 'std::basic_ios<_Elem,_Traits>::basic_ios' : cannot access private member declared in class 'std::basic_ios<_Elem,_Traits>'
    On which line is that?
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  7. #7
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    i cant tell , it directly goes to fstream!!!

  8. #8
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    i cant tell , it directly goes to fstream!!! when i click on error

  9. #9
    C++ Witch laserlight's Avatar
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    Take a look at your previous error message:
    d:\backup_qi-287\geconfidential\rajesh\hitachi_runner_blade\cod e_runner_blade\runner_blde\runner_blde\deffile.cpp (28) : error C2275: 'std::ifstream' : illegal use of this type as an expression
    See the part that I bolded? That's the line number. Look for that in your current error message.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  10. #10
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    sorry went for lunch, i am not been able to find it .i have pasted whole stack here!!










    1>------ Build started: Project: runner_blde, Configuration: Debug Win32 ------
    1>Compiling...
    1>defFile.cpp
    1>d:\apps\microsoft visual studio 8\vc\include\fstream(675) : error C2248: 'std::basic_ios<_Elem,_Traits>::basic_ios' : cannot access private member declared in class 'std::basic_ios<_Elem,_Traits>'
    1> with
    1> [
    1> _Elem=char,
    1> _Traits=std::char_traits<char>
    1> ]
    1> d:\apps\microsoft visual studio 8\vc\include\ios(151) : see declaration of 'std::basic_ios<_Elem,_Traits>::basic_ios'
    1> with
    1> [
    1> _Elem=char,
    1> _Traits=std::char_traits<char>
    1> ]
    1> This diagnostic occurred in the compiler generated function 'std::basic_ifstream<_Elem,_Traits>::basic_ifstrea m(const std::basic_ifstream<_Elem,_Traits> &)'
    1> with
    1> [
    1> _Elem=char,
    1> _Traits=std::char_traits<char>
    1> ]
    1>Build log was saved at "file://d:\Backup_QI-287\GEConfidential\rajesh\Hitachi_runner_blade\cod e_runner_blade\runner_blde\runner_blde\Debug\Build Log.htm"
    1>runner_blde - 1 error(s), 0 warning(s)
    ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

  11. #11
    The larch
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    Streams are non-copiable and their copy constructors are private for that reason.

    Are you trying to pass a stream to a function by value? You can't do that and must pass a reference.
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).

  12. #12
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    hi anon,

    i tried passing it with reference but it is giving below error,


    d:\backup_qi-287\geconfidential\rajesh\hitachi_runner_blade\cod e_runner_blade\runner_blde\runner_blde\deffile.cpp (28) : error C2275: 'std::ifstream' : illegal use of this type as an expression

  13. #13
    The larch
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    The code in the first post?

    Whether something is passed by reference or by value is determined where the function is declared/defined, not where it is called.

    Example of a function that takes a reference.
    Code:
    void foo(std::istream& is); //declaration
    
    //implementation
    void foo(std::istream& is) 
    {
    }
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).

  14. #14
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    anon i dont want to use istream !! i am using ifstream!!!after declaring as u said i get this error!

    error C2275: 'std::ifstream' : illegal use of this type as an expression

  15. #15
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    thanks got it!!!!!!!!!!!!!!!

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