unexpected input stream behavior

[Maarten Ditzel]

Hi,

I ran into a some unexpected behavior (at least by me) when running the
following code:

/**********************************************************************************/

#include <iostream.h>
#include <map>
#include <string>

int main(int argc, char *argv[]) {

  map<string, string> M;

  string key = "blaat";  

  // unexpected behavior
  cin >> key >> M[key];       // first input
  cin >> key >> M[key];       // second input

  // should be the same ???
  cin >> key;                 // third input (a)
  cin >> M[key];              // third input (b)

  // print complete map
  map<gcc --verstring, string>::const_iterator iter;
  for (iter=M.begin(); iter!=M.end(); iter++) {
    cout << iter->first << '\t' << iter->second << endl;
  }

  return 0;
}

/**********************************************************************************/

I compiled it using g++ version 2.95.4 on a debian system (mostly
Woody).
Running it with the following inputs:
>>>>>>>>>>>>>>>>>>>>>>>>>
first 1st
second 2nd
third 3rd
>>>>>>>>>>>>>>>>>>>>>>>>>

gives:
>>>>>>>>>>>>>>>>>>>>>>>>>
blaat   1st
first   2nd
third   3rd
>>>>>>>>>>>>>>>>>>>>>>>>>

So what obviously happens is that in the first and second input
statements, the previous key value is used in M[key]. This does not
happen using the 3rd input statements (a and b). 
I expected the first and second input statements to act the same as the
third, basically

cin >> a >> b;    
equals
cin >> a; cin >> b;

I don't know if this is unspecified C++ behavior, or possibly a bug in
the standard libraries or compiler.
Any ideas/comments ?

Regards,
Maarten Ditzel

-- 

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ir. Maarten Ditzel                 Delft University of Technology 
                                           Electrical Engineering 
ditzel@cobalt.et.tudelft.nl                  Circuits and Systems
http://cobalt.et.tudelft.nl/~ditzel     Ubiquitous Communications
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