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Ambiguous symbol error

Posted on 2001-07-03
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Last Modified: 2007-11-27
Hi,
The following snippet cause a compilation error:

...
using namespace std;

ifstream fin;
...


error C2872: 'ifstream' : ambiguous symbol

How can I solve it?
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Question by:s_lavie
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12 Comments
 
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Expert Comment

by:GloriousRain
ID: 6248093
try ifstream::ifstream fin;
0
 
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Author Comment

by:s_lavie
ID: 6248143
I did and I got:
error C2146: syntax error : missing ';' before identifier 'fin'
error C2277: 'ifstream::ifstream' : cannot take address of this member function
0
 
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Expert Comment

by:nietod
ID: 6248181
We probably need to see more code, but did you remember to include <fstream>, the include file that defines the ifstream class--and lots of other file stream classes?
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Expert Comment

by:MDarling
ID: 6248183
Did you include the header?

...

#include <fstream>

using namespace std;

ifstream fin;

...


Regards,
mike.
0
 
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Expert Comment

by:MDarling
ID: 6248187
Mine is the same comment as nietod (which wasn't there until I pressed submit).

Regards,
Mike.
0
 
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Author Comment

by:s_lavie
ID: 6248224
Here is the code:

#include <fstream.h>
#include <vector>

using namespace std;

int main()
{
     ifstream fin; // the line that causes the above-mentioned error

     return 0;
}

Note: #include <vector> is a must, since I use it later...
0
 
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Accepted Solution

by:
nietod earned 50 total points
ID: 6248257
The problem is that you are using the wrong header.  Replace <fstream.h> with <fstream>

I have an explaination that I have to find.
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Expert Comment

by:nietod
ID: 6248272
The official STL (Standard Template Library) files are all extensionless files, like <iostream>, <vector>, and <list>.  You may find that your compiler has files with these names but a .h extension, like <iostream.h>, <vector.h>, and <list.h> but these are not the standard files.  These files are old, non-standard files that are provided for compativbility for old programs that used them before the standard files were settled upon.  You want to avoid usign this files if you have the standard ones availalbe.  The non-stnadard files may not have all the features of the standard ones, they also likely to have more bugs and other problems, and also since they are not standardized, they will varry from compiler to compiler, and might not even exist on many compilers.  So avoid using these files if you have the extenionless, standardized files.

Now there is one big difference between the standardized files and many of the non-standardized files.  The standardized files place all of their symbolic names in the "std" namespaces.  This is so that the names defined in these files don't clash with names you write in your program.  So in order to access the names inside the standard STL files you need to prefix them with "std::" like

std::vector<std::string> StringArray;

If you do not wish to use those "std::",  you can instead add a using directive like

using namespace std;

after you include the STL  include files.  Then these names will all be brought into your namespace.
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Author Comment

by:s_lavie
ID: 6248275
Thanks nietod, but I would like to see the explaination!
0
 
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Author Comment

by:s_lavie
ID: 6248286
Thanks nietod, but I would like to see the explaination!
0
 
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Expert Comment

by:nietod
ID: 6248308
Well you got it.  Proposed as an answer on a question with an accepted answer?   Try not to think about that it causes headaches.
0
 
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Author Comment

by:s_lavie
ID: 6248374
Network problems... thanks anyway!
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