Re: c++ code - C / C++ / MFC Discussion Boards

Re: error C2491: 'XXX'::entries' : definition of dllimport function not allowed

Andraw11119-Jul-12 5:35

19-Jul-12 5:35

Yes, you are right.

I just change to dllexport, then I can add function implementation to it, so can be used by other class inside this DLL.

Thanks!

error C2679: binary '!=' : no operator found which takes a right-hand operand of type 'int' In VS2008

Andraw11119-Jul-12 4:20

Andraw111

19-Jul-12 4:20

Hi, dear all,

I create a class name Point2D to store coordinate value, with "<" and "==" two operators overloadings.

Then create a type based on it as:

typedef std::vector<Point2D*> Point2D_Vector;

Point2D_Vector PointVector;

Then add some data to PointVector.

When I loop the vector:

Point2D_Vector::iterator itr;
for (itr=PointVector.begin(); itr!=PointVector.end(); itr++)
if (itr != 0)
delete *itr;

They work fine in C++6.0, now when I try to compile it in VS2008 I got the error message in if(itr != 0) line:

error C2679: binary '!=' : no operator found which takes a right-hand operand of type 'int' (or there is no acceptable conversion)

How can I solve this issue? Thanks!

Re: error C2679: binary '!=' : no operator found which takes a right-hand operand of type 'int' In VS2008

C^hris L^osinger19-Jul-12 4:27

C^hris L^osinger

19-Jul-12 4:27

C++

if ((*itr)!=0)

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Re: error C2679: binary '!=' : no operator found which takes a right-hand operand of type 'int' In VS2008

Stephen Hewitt19-Jul-12 4:27

Stephen Hewitt

19-Jul-12 4:27

The statement itr != 0 makes no sense. Even when it compiled in VC6 it wasn't doing what it looks like you intended (to stop deleting a NULL pointer). You probably mean this:

if (*itr != 0)

Also, deleting a NULL pointer is safe in C++ (it does nothing). The check is not needed and it potentially makes the code less efficient as the compiler inserts code to check for this automatically.

Steve

Re: error C2679: binary '!=' : no operator found which takes a right-hand operand of type 'int' In VS2008

Andraw11119-Jul-12 4:35

Andraw111

19-Jul-12 4:35

Thanks, Chris and Steve, it can be compiled now.

c++ code

phineas kimathi19-Jul-12 2:46

phineas kimathi

19-Jul-12 2:46

a code to change string to uppercase using integer values within the code.

Re: c++ code

Richard MacCutchan19-Jul-12 3:21

Richard MacCutchan

19-Jul-12 3:21

There are built in library and MFC functions to perform this. Please explain what you mean by "change string to uppercase using integer values"?

One of these days I'm going to think of a really clever signature.

Re: c++ code

Rajesh R Subramanian19-Jul-12 3:34

Rajesh R Subramanian

19-Jul-12 3:34

Hint: There's an offset of 32 between lower and upper cased letters. For example, the ascii value (int) of lower case 'c' is 99, and the same of upper case 'C' is 67.

"Real men drive manual transmission" - Rajesh.

Re: c++ code

Software_Developer19-Jul-12 6:52

Software_Developer

19-Jul-12 6:52

The integer difference between a lowercase char and a uppercase char when subtracted is 32.
simply subtract the lowercase by 32 to get a uppercase char.

#include <stdio.h>
#include <string.h>

int main(void)
{
	char strchr[32] = "the quick fox";
	int strlength=strlen(strchr);

        printf("Before\n" );
	printf("%s\n\n", strchr);
 
	for (int i=0; i<strlength; i++) 
	{
		if((strchr[i] >= 97) && (strchr[i] <= 122)) 
		{
			strchr[i] = strchr[i] -32;
			
		}
	}
        printf("After\n" );	 
	printf("%s\n\n", strchr);

return(0);

}

Re: c++ code

Richard MacCutchan19-Jul-12 22:20

Richard MacCutchan

19-Jul-12 22:20

Using hexadecimal rather than decimal integer values makes the code much more readable.

One of these days I'm going to think of a really clever signature.

Re: c++ code

David Crow20-Jul-12 2:29

David Crow

20-Jul-12 2:29

TopCoder23 wrote:
char strchr[32] = "the quick fox";

I would consider a different variable name as strchr is the name of a CRT function.

TopCoder23 wrote:
if((strchr[i] >= 97) && (strchr[i] <= 122))

What about:

if (islower(strchr[i]))
    strchr[i] = toupper(strchr[i]);

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Re: c++ code

Software_Developer20-Jul-12 3:30

Software_Developer

20-Jul-12 3:30

You're right about strchr() . and islower(). http://www.cplusplus.com/reference/clibrary/cstring/strchr/[^]

Error happen when open file while migrate VC++ 6 to VS2008

Andraw11118-Jul-12 9:16

Andraw111

18-Jul-12 9:16

Hi,dear all,

I have a project created using C++ 6.0. Now I need to update it to VS2008, now I have a problem when I try to open a file.

In C++ 6.0
#include <fstream.h>
ifstream INPFile(INPFileName, ios::nocreate);

In VS2008

#include <fstream>
ifstream INPFile(INPFileName, ios::nocreate);

the second line get the following error:
Error 23 error C2039: 'nocreate' : is not a member of 'std::basic_ios<_Elem,_Traits>'

Error 24 error C2065: 'nocreate' : undeclared identifier

If I change the second line to the following:

ifstream INPFile(INPFileName)

then get new error as following
error 2248: 'std::basic_ios<_Elem,_Traits>::basic_ios' : cannot access private member declared in class 'std::basic_ios<_Elem,_Traits>'

How can I solve this issue?

Thanks!

Re: Error happen when open file while migrate VC++ 6 to VS2008

Albert Holguin18-Jul-12 9:47

Albert Holguin

18-Jul-12 9:47

This talks about the reason for the first error:
http://www.devx.com/tips/Tip/14544[^]

After your change however, the error about the private member doesn't make sense, you probably need to show a bit more of your code.

Re: Error happen when open file while migrate VC++ 6 to VS2008

Andraw11118-Jul-12 10:01

Andraw111

18-Jul-12 10:01

Albert, thanks for your quick reply.

My project has around 50 files, I already search all header files to check if any function pass fstream as argument, and modify them all to be passed as reference instead of as object.

I don't understand why if I use following code:

ifstream fin(OutputF, ios::in,ios::nocreate);

I got error like "C2039: 'nocreate' : is not...", but if I modify it to:
ifstream fin(OutputF, ios::in,ios::_Nocreate);
I got other kind of error messge:
"error C2248: 'std::basic_ios<_Elem,_Traits>::basic_ios' : cannot access private.."

Thanks!

Re: Error happen when open file while migrate VC++ 6 to VS2008

Albert Holguin18-Jul-12 11:35

Albert Holguin

18-Jul-12 11:35

Wait, if you're doing an ifstream (input), why are you specifiying "no create" at all? That doesn't make sense, it's not going to get created if it can't find it. That's only even applicable at all if you're opening in read/write or write modes.

Re: Error happen when open file while migrate VC++ 6 to VS2008

Richard MacCutchan18-Jul-12 21:59

Richard MacCutchan

18-Jul-12 21:59

I do not think the nocreate option exists anymore, and it should not be necessary on an input stream. You need to use the latest definitions as described here[^].

One of these days I'm going to think of a really clever signature.

Re: Error happen when open file while migrate VC++ 6 to VS2008

Andraw11119-Jul-12 3:29

Andraw111

19-Jul-12 3:29

Thanks, Albert and Richard,

Both of you are right, yes, there is no nocreate.

I solve it by remove it, but the main reason I got the " cannot access private member ..." error is that I have some functions that pass ifstream object as value, they should be passed by reference.

Thanks again!

Re: Error happen when open file while migrate VC++ 6 to VS2008

Andraw11119-Jul-12 5:40

Andraw111

19-Jul-12 5:40

Hi,

I solve my issue posted yesterday, but today has another problem related to it.

When I migrate another small project from C++ to VS2008, I double check all the function delcaration to make sure fstream object is passed by reference or pointer, but when I compile program, I still got two error messages, they are same and the only two errors.

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

In this case how should I find where the error come from?

Re: Error happen when open file while migrate VC++ 6 to VS2008

Andraw11119-Jul-12 6:17

Andraw111

19-Jul-12 6:17

I found some functions that pass std::istream or std::istrstream by value, not by reference, is that the reason to cause the problem?

Re: Error happen when open file while migrate VC++ 6 to VS2008

Andraw11119-Jul-12 6:25

Andraw111

19-Jul-12 6:25

Yes, they also need to be passed by reference, now can be compile now.

Re: Error happen when open file while migrate VC++ 6 to VS2008

jschell20-Jul-12 7:15

jschell

20-Jul-12 7:15

I would suppose that passing the fstream by value in 6.0 was wrong too. It might have worked but only by luck.

A fstream is a representation of a computer resource. Passing by value implicitly duplicates the representation without duplicating the actual resource. Thus it represents a broken design/implementation.

search for a word in a text file

byank18-Jul-12 2:14

byank

18-Jul-12 2:14

PLease show me how to search for a word in a text file using a listbox, String objects and Indexof, after i opened it in a richtextbox ,in visual C++, please help!!

Re: search for a word in a text file

David Crow18-Jul-12 2:18

David Crow

18-Jul-12 2:18

byank wrote:
PLease show me how to search for a word in a text file using a listbox...

What does a listbox have to do with searching a file?

Are you using MFC or Win32?

Re: search for a word in a text file

byank19-Jul-12 11:00

byank

19-Jul-12 11:00

it's just that i've seen here on codeproject the code for searching words in a text files using vb, i think. I need it in c++. thanks

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