File.is_open() or File.fail() ?

What's best?
if ( File.is_open() ) or
if (! File.fail() )

What I mean is, do these functions do more then the obvius which I should know about hwne chusing.

I'm asking because fail() is const and is_open isn't.

well in your case may be not.. but conside a program where you have to check if a file is opened... So here u use the 2nd one and the fail one is used to see if a file failed to open...

Sounds like the same thing.

So File.is_open() == !File.fail() ???

no they are not the same in the context i have used them.... See i write a program to check the files that are currently opened by the user.... and here i would try to open each file and check if it failed.. I would just like to check if it is opened.....

I always write like this:

Code:

---


ifstream fin("file.txt");
if (fin)
{
  ...
}

---

hmm... didn't know you could do that... what kind of overloated operater have they used to do that?

good question. I have wondered that myself. Is it something like overloading "if" or "!" ?

~Inquirer

Quote:

---

Originally posted by Inquirer
good question. I have wondered that myself. Is it something like overloading "if" or "!" ?

~Inquirer

---

Not too sure...but I think it may be operator void*() which returns NULL if the failbit is set

but void functions doesn't return anything. That's the point about void. :)

Quote:

---

Originally posted by Zahl
but void functions doesn't return anything. That's the point about void. :)

---

(void) != (void*)

why doesn't it just return *, and doesn't * mean that it's somekind of pointer... well then a pointer to what.
String * or Char * or int * or...

http://www.cee.hw.ac.uk/~rjp/Coursew.../voidstar.html

To answer the OP's question, I prefer to be explicit in what I want so there is no confusion such as in this thread. ;)

Code:

---

std::ifstream input_file ( "something.ext" );

if ( input_file.is_open() ) {
  // Work with the file.
}
else {
  // Report the error and handle
}

---

-Prelude

Hey Prelude, maybe you, too, could ansver a question I maid two days ago here http://cboard.cprogramming.com/showt...threadid=26709 but never got an ansver on.

Sorry, I can't reproduce the problem on either MSVC++ or Borland.

-Prelude

Funny since I use Borland 6.0... Glad you tryed though. It just doesn't make much sense that when I use the for loop to set every part of the array equal '\0' it works. Especially since this shoudln't be the way to do it. (or necesary)