Using fstream Object as a Function Parameter

Question

#include <iostream.h>
#include <fstream.h>
#include <stdlib.h>

void vowel(fstream a){
    char ch;
    int ctr = 0;
    while(!a.eof()){
        a.get(ch);
        if (ch == 'A' || ch == 'E' || ch == 'I' || ch == 'O' || ch == 'U'){
            cout << ch;
            ctr++;
        }
    }
    cout << "Number of Vowels: " << ctr;
}

main(){
    fstream a;
    a.open("temp.txt", ios::in);
    vowel(a);
return 0;
}

In this simple program , I am trying t count the number of caps Vowels in the file temp.txt. However, I am getting the error:

ios::ios(ios &) is not accessible in function fstream::fstream(fstream&)

Instead opening the file in the function itself does the job. Why is it so? Thanks a lot

NB:

How do I use fstream (specifically ofstream) through a functions parameters

Here it says, that it should work the way I am trying.

Rick

Answer 1

You need to pass the fstream by reference:

void vowel(fstream& a){ .... }
//                ^ here!

Answer 2

An fstream object is not copyable. Pass by reference instead: fstream&:

void vowel(fstream& a)

Note you can avoid the call to open() by providing the same arguments to the constructor:

fstream a("temp.txt", ios::in);

and don't use while(!a.eof()), check the result of read operations immediately. The eof() will only be set when an attempt is made to read beyond the last character in the file. This means that !a.eof() will be true when the previous call to get(ch) read the last character from the file, but subsequent get(ch) will fail and set eof but the code won't notice the failure until after it has processed ch again even though the read failed.

Example correct structure:

while (a.get(ch)) {