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Can functions that return int, take files as parameters.

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Can functions that return int, take files as parameters.

 
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  #1
32 Days Ago
So far, I have only read about using void functions to take on ifstreams as a parameter. Yet I want to be able to make a single function that takes a file of numbers as a parameter, and do some calculation to each number. I can do this with a void function pretty easily, but I want a separate the calculations and the opening of the file. How do I do this?

for an example Ill show you these prototypes.
//works
void average( ifstream& file_in);
//doesnt work to my knowledge
int average(ifstream& file_in);

Ps I am away from my computer with my code, and my compiler.
No arrays please I havent learned that yet!
Last edited by jascase901; 32 Days Ago at 8:50 pm.
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  #2
32 Days Ago
>//doesnt work to my knowledge
>int average(ifstream& file_in);
The parameters and return type are not dependent. If that prototype doesn't work, it's because you did something else wrong. How about posting a complete program that fails?
I'm here to prove you wrong.
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  #3
32 Days Ago
Ill be away from my comp with the program for a few hours, but thanks for the answer. I spent like an hour google searching for that and found nothing.
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  #4
32 Days Ago
here is the code

C++ Syntax (Toggle Plain Text) 
  1. #include <fstream>
  2. #include <iostream>
  3. #include <cstdlib>
  4. #include <cctype>
  5. using namespace std;
  6.  
  7. void open_file(ifstream& fin);
  8. //Precondition: The File Written.dat must exist
  9. //Postcondition: opens that file
  10.  
  11. double calc_average(ifstream& fin);
  12. //Precondition, file must be opened and linked
  13. //Takes the average of a list of numbers
  14.  
  15.  
  16. int main()
  17. {
  18.     double average;
  19.     ifstream file_in;
  20.  
  21.     open_file(file_in);
  22.     average=calc_average(file_in);
  23.  
  24. }
  25.  
  26.  
  27.  
  28.  
  29. void open_file(ifstream& fin)
  30. {
  31.     fin.open("written.dat");
  32.     if (fin.fail())
  33.     {   
  34.         cout<<"fin failed line 26";
  35.         exit(1);
  36.     }   
  37. }
  38.  
  39.  
  40.  
  41.  
  42. double calc_average(fin)
  43. {
  44.     double next, sum;
  45.     int count=0;
  46.  
  47.     while (fin>>next)
  48.     {   
  49.         sum=next+sum;
  50.         count++;
  51.     }   
  52.  
  53.     return (sum/count);
  54. }
Last edited by jascase901; 32 Days Ago at 11:02 pm. Reason: wrong code
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  #5
32 Days Ago
call your calc_average inside openFile function. 
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  #6
32 Days Ago
main function should return a value
C++ Syntax (Toggle Plain Text) 
  1. int main()
  2. {
  3. 		.
  4. 		.
  5. 		.
  6. 		.
  7. 		.
  8. 		.
  9.  
  10. 		return 0;
  11. }


double calc_average(ifstream& fin)
C++ Syntax (Toggle Plain Text) 
  1. double calc_average(fin)
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