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Adding binary values from a file

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Adding binary values from a file

 
0
  #1
Dec 16th, 2006
Hello, I'm working o a function that takes a file with binary numbers and returns the sum of those numbers. Here's where I'm now

C++ Syntax (Toggle Plain Text) 
  1. int Sum (char *fileName)
  2. {
  3. char * numEnd;
  4. long temp(0);
  5. int result(0);
  6. string line;
  7.  ifstream file (fileName);
  8.   if (file.is_open())
  9.   {
  10.     while (! file.eof() )
  11.     {
  12.       getline (file,line);
  13. //Convert line to an long and sum up with the rest 
  14.       temp = strtol(line, &numEnd, 2);
  15.       result = result + temp;    
  16. //Done
  17.     }
  18. // close the stream
  19.     file.close();
  20.   }
  21. return result;
  22. }

and here's an error I'm getting when building it:
error C2664: 'strtol' : cannot convert parameter 1 from 'std::string' to 'const char *'

I thought strtol needed a pointer to the string, but changing line to pointer to line didn't help. Anyone can point me in a right direction?
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Re: Adding binary values from a file

 
0
  #2
Dec 16th, 2006
OK, I got it. Any comments on code quality or improvements are still welcome!

C++ Syntax (Toggle Plain Text) 
  1. int Sum (char *fileName)
  2. {
  3. char * numEnd;
  4. long temp(0);
  5. int result(0);
  6. string line;
  7.  ifstream file (fileName);
  8.   if (file.is_open())
  9.   {
  10.     while (! file.eof() )
  11.     {
  12.       getline (file,line);
  13. //Convert line to an int and sum up with the rest 
  14.       char *linePt = &line[0];
  15.       temp = strtol(linePt, &numEnd, 2);
  16.       result = result + temp;    
  17. //Done
  18.     }
  19. // close the stream
  20.     file.close();
  21.   }
  22. return result;
  23. }
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Re: Adding binary values from a file

 
1
  #3
Dec 17th, 2006
It's because strtol was an old C function written far before C++ strings were invented. Although C++ strings have overloaded functions to make transitions from the older-style char strings to C++ strings and vice-versa, this problem can't be as transparently solved when passing a C++ string to a function that is expecting a char string. To remedy this, C++ strings include a nifty member function called c_str() that can quickly return the char string equivalent. Thus, you could code it like this:
C++ Syntax (Toggle Plain Text) 
  1. temp = strtol(line.c_str(), &numEnd, 2);

Better yet, use the C++ streams, the modern equivalent of a lot of the old C string functions, rather than mixing C and C++.

Hope this helps
"Technological progress is like an axe in the hands of a pathological criminal."
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