Question

I’m trying to move from stdio to iostream, which is proving very difficult. I’ve got the basics of loading a file and closing them, but I really don’t have a clue as to what a stream even is yet, or how they work.

In stdio everything’s relatively easy and straight forward compared to this. What I need to be able to do is

1. Read a single character from a text file.
2. Call a function based on what that character is.
3. Repeat till I’ve read all the characters in the file.

What I have so far is.. not much:

int main()
{
    std::ifstream("sometextfile.txt", std::ios::in);
    // this is SUPPOSED to be the while loop for reading.  I got here and realized I have 
    //no idea how to even read a file
    while()
    {
    }
return 0;
}

What I need to know is how to get a single character and how that character is actually stored(Is it a string? An int? A char? Can I decide for myself how to store it?)

Once I know that I think I can handle the rest. I’ll store the character in an appropriate container, then use a switch to do things based on what that character actually is. It’d look something like this.

int main()
{
    std::ifstream textFile("sometextfile.txt", std::ios::in);

    while(..able to read?)
    {
        char/int/string readItem;
        //this is where the fstream would get the character and I assume stick it into readItem?
        switch(readItem)
        {
        case 1:
            //dosomething
              break;
        case ' ':
            //dosomething etc etc
              break;
        case '\n':
        }
    }
return 0;
}

Notice that I need to be able to check for white space and new lines, hopefully it’s possible. It would also be handy if instead of one generic container I could store numbers in an int and chars in a char. I can work around it if not though.

Thanks to anyone who can explain to me how streams work and what all is possible with them.

Answer 1

You also can abstract away the whole idea of getting a single character with streambuf_iterators, if you want to use any algorithms:

#include <iterator>
#include <fstream>

int main(){
  typedef std::istreambuf_iterator<char> buf_iter;
  std::fstream file("name");
  for(buf_iter i(file), e; i != e; ++i){
    char c = *i;
  }
}