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fstream problem.

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Join Date: Oct 2008

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imput1234

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fstream problem.

Nov 25th, 2008

Hey,

I'm trying to only read the int's and the symbol - (negative) from the file.

right now my code is where m,d, and y are dates.
Everything works fine. Except I do not read the - symbol.

Any one know how to solve this?

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fin.open(ifile.c_str());
fin >> m1 >> c >> d1 >> c >> y1;
fin >> m2 >> c >> d2 >> c >> y2;
fin >> m3 >> c >> d3 >> c >> y3;
fin.close();

For example date -10/-1/1999

will be read as 10/1/1999

for my assignment I must read the negative symbol.

Thanks

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Join Date: Aug 2007

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vmanes

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Re: fstream problem.

Nov 25th, 2008

What are the data types of the variables?

With the mdy variables as ints and the c as a char, it seems to work for me - I get the negative values.

A full code sample illustrating your problem will help us help you.

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Join Date: Oct 2008

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imput1234

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Re: fstream problem.

Nov 25th, 2008

Nevermind, weird it works now. I havent;' made any changes.

But I do have another problem.

I'm trying to make the program so that, if the user does not enter a valid file name, it will output that and clsoe the program.

This is what I have so far, and no matter what the user enters, the console will go in to a failstate. Anyone know why

Thanks.

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	ifstream fin;

	cout << "Enter filename: ";
	getline(cin, ifile);	

    
	if ( !ifile.size() == 0 )
	{	
		cout << "No file found." << endl;
		system ("PAUSE");
		return 1;
	}

	fin.open(ifile.c_str());

Last edited by imput1234; Nov 25th, 2008 at 2:08 am.

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vmanes

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Re: fstream problem.

Nov 25th, 2008

That should work. Please post the exact data file contents you're trying to read.

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imput1234

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Re: fstream problem.

Nov 25th, 2008

edited original post.

ifile is a string.

Last edited by imput1234; Nov 25th, 2008 at 2:09 am.

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imput1234

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Re: fstream problem.

Nov 25th, 2008

I've also tried

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	if ( !ifile.empty() )
	{	
		cout << "No file found." << endl;
		system ("PAUSE");
		return 1;
	}

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Join Date: Aug 2007

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vmanes

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Re: fstream problem.

Nov 25th, 2008

And, the test you're doing is only testing the filename the user entered, it does not test if there's actually a file or if it has any content.

(this should have come after my next reply - they got out of order somehow)

Last edited by vmanes; Nov 25th, 2008 at 2:23 am.

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vmanes

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Re: fstream problem.

Nov 25th, 2008

You're asking a question that's not exactly what I think you mean.

if ( (! ifile.size( ) ) == 0 ) means, logically negate the value the size function returns, giving you a boolean true or false value, then compare that to zero, which is considered false.

If you're trying to find out if the user actually entered some string as the file name, try

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
if( ifile.size( ) == 0 )
{
   //error handler
}
else
{
    fin.open( ifile.c_str( ) );
}
if( ifile.size( ) == 0 )
{
   //error handler
}
else
{
    fin.open( ifile.c_str( ) );
}

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cikara21

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Re: fstream problem.

Nov 25th, 2008

If failed to open..

 Help with Code Tags 
 c++ Syntax (Toggle Plain Text) 
if (fin.fail())
   cout<<"file does not exist";
if (fin.fail())
   cout<<"file does not exist";

Last edited by cikara21; Nov 25th, 2008 at 2:39 am.

$.:-cikara21-:.$

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imput1234

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Re: fstream problem.

#10

Nov 25th, 2008

I've tried those. They don't work.
This is my problem.
Lets say the user enters hello.txt
but hello.txt does not exist.
How can I make the program say "Does not exist"
That is what I have been trying to do.
all the previous methods don't do that, they just make the dates really long numbers.

Hope that makes more sense.