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Doing something stupid with stringstream

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Doing something stupid with stringstream

 
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  #1
Jan 20th, 2009
I put together this little example to test my sanity, and it failed!

C++ Syntax (Toggle Plain Text) 
  1. #include <iostream>
  2. #include <fstream>
  3. #include <vector>
  4. #include <string>
  5. #include <sstream>
  6.  
  7. using namespace std;
  8.  
  9. /* Example.txt
  10. 23
  11. test
  12. 4.5
  13. */
  14.  
  15. int main(int argc, char *argv[])
  16. {
  17. 	string Filename = argv[1];
  18. 	cout << "Filename: " << Filename << endl;
  19.  
  20. 	int Integer;
  21. 	string String;	
  22. 	double Double;
  23.  
  24. 	ifstream fin(Filename.c_str());
  25.  
  26. 	string line;
  27. 	stringstream linestream;
  28.  
  29. 	getline(fin, line);
  30. 	linestream.str("");
  31. 	linestream << line;
  32. 	linestream >> Integer;	
  33.  
  34. 	getline(fin, line);
  35. 	linestream.str("");
  36. 	linestream << line;
  37. 	linestream >> String;
  38.  
  39. 	getline(fin, line);
  40. 	linestream.str("");
  41. 	linestream << line;
  42. 	linestream >> Double;
  43.  
  44. 	fin.close();
  45.  
  46. 	cout << "Integer: " << Integer << endl;
  47. 	cout << "String: " << String << endl;
  48. 	cout << "Double: " << Double << endl;
  49.  
  50. 	return 0;
  51. }

The output is

C++ Syntax (Toggle Plain Text) 
  1. Filename: Example.txt
  2. Integer: 65535
  3. String: 
  4. Double: 4.86439e-270

Can anyone spot the stupid bug?

Thanks,

Dave
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Re: Doing something stupid with stringstream

 
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  #2
Jan 20th, 2009
A stringstream is still a stream. When you read to end-of-file, you need to clear the state before you can do anything substantial with the stream again:
C++ Syntax (Toggle Plain Text) 
  1. linestream.clear();
  2. linestream << line;
  3. ...
I'm here to prove you wrong.
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Re: Doing something stupid with stringstream

 
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  #3
Jan 20th, 2009
That's what I thought I was doing with
C++ Syntax (Toggle Plain Text) 
  1. linestream.str("");

But I changed all of those to

C++ Syntax (Toggle Plain Text) 
  1. linestream.clear()

And I get the same garbage results.

Dave
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Re: Doing something stupid with stringstream

 
0
  #4
Jan 20th, 2009
I get correct results with the following code. The only changes were the ones you claim to have made:
C++ Syntax (Toggle Plain Text) 
  1. #include <iostream>
  2. #include <fstream>
  3. #include <vector>
  4. #include <string>
  5. #include <sstream>
  6.  
  7. using namespace std;
  8.  
  9. /* Example.txt
  10. 23
  11. test
  12. 4.5
  13. */
  14.  
  15. int main(int argc, char *argv[])
  16. {
  17. 	string Filename = argv[1];
  18. 	cout << "Filename: " << Filename << endl;
  19.  
  20. 	int Integer;
  21. 	string String;	
  22. 	double Double;
  23.  
  24. 	ifstream fin(Filename.c_str());
  25.  
  26. 	string line;
  27. 	stringstream linestream;
  28.  
  29. 	getline(fin, line);
  30. 	linestream << line;
  31. 	linestream >> Integer;	
  32.  
  33. 	getline(fin, line);
  34. 	linestream.clear();
  35. 	linestream << line;
  36. 	linestream >> String;
  37.  
  38. 	getline(fin, line);
  39. 	linestream.clear();
  40. 	linestream << line;
  41. 	linestream >> Double;
  42.  
  43. 	fin.close();
  44.  
  45. 	cout << "Integer: " << Integer << endl;
  46. 	cout << "String: " << String << endl;
  47. 	cout << "Double: " << Double << endl;
  48.  
  49. 	return 0;
  50. }
I'm here to prove you wrong.
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Re: Doing something stupid with stringstream

 
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  #5
Jan 20th, 2009
Just tested it with the changes mentioned, and it works for me too.
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Re: Doing something stupid with stringstream

 
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  #6
Jan 20th, 2009
haha OH NO! The file was in the wrong directory... it works now.

I didn't gaurd it with
C++ Syntax (Toggle Plain Text) 
  1. if(fin == NULL)

because it was just a toy example... but clearly I should have!

Sorry for the silly mistake.

Dave
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Re: Doing something stupid with stringstream

 
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  #7
Jan 20th, 2009
I'd think about how to check if a file is really open
Knowledge is power -- But experience is everything
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