C / C++ / MFC Discussion Boards

Re: If 1 = true, 0 =false, why return 0 = successful?

Link260025-May-03 3:01

25-May-03 3:01

<quote>So true (1) indicates success, false (0) indicates failure.

That's excatly why I'm confusing. In the boolean value, true is 1 and it
should indicate succeeded. But we use return 0; to indicate successful,
don't we? But of course the return type is int and it is not boolean.

I wonder can we do this to indicate succeeded?

bool main()
{

// codes here

return true;
}

Re: If 1 = true, 0 =false, why return 0 = successful?

ZoogieZork25-May-03 10:00

ZoogieZork

25-May-03 10:00

VW_Red_Jetta wrote:
I wonder can we do this to indicate succeeded?

bool main()
{

// codes here

return true;
}

Nope. Comparing boolean return values to int return values is much like comparing apples to asparagus. As others have mentioned, there's no deep philosophical reason for the apparent contradiction in terms; merely that's the way it is technically.

If it makes you feel a bit better, you can always do this:

#include <stdlib.h><br />
<br />
int main(int argc,char **args) {<br />
<br />
  /* Code, code, code... */<br />
<br />
  return EXIT_SUCCESS;<br />
}

- Mike

Re: If 1 = true, 0 =false, why return 0 = successful?

Link260025-May-03 11:30

Link2600

25-May-03 11:30

Some questions about EXIT_SUCCESS: is it always capitalized? Can I
return exit_success? And is it deifined in stdlib.h?

I once have a trouble understanding what does it do and I'm still
having trouble with it too. Could you tell me what does
EXIT_FAILURE do? How does it return on error? Is there any alternative
to this method?

int main()
{
.
.
.

// open input and exit on error.
if(ins.fail())
{
cerr << "ERROR: cannot open";

return EXIT_FAILURE;
}

.
.
.
}

Re: If 1 = true, 0 =false, why return 0 = successful?

ZoogieZork25-May-03 14:32

ZoogieZork

25-May-03 14:32

VW_Red_Jetta wrote:
Some questions about EXIT_SUCCESS: is it always capitalized?

Yes, all identifiers in C and C++ are case-sensitive.

VW_Red_Jetta wrote:
And is it deifined in stdlib.h?

Yes, you can check for yourself... there will probably be a line like:

<br />
#define EXIT_SUCCESS 0<br />

VW_Red_Jetta wrote:
Could you tell me what does
EXIT_FAILURE do? How does it return on error?

The return value from main() in C/C++ is passed back to the parent process or the operating system. It's a good idea to use EXIT_SUCCESS and EXIT_FAILURE, particularly for command-line apps. In Unix (dunno about Win32), the return code can be useful when your program is being run as part of a script (I won't get into the crazy world of Unix shell scripting here).

Of course, in many cases, nobody is really listening to the return value. However, it's good to get into the habit of properly returning exit codes as defined by the language or API.

VW_Red_Jetta wrote:
Is there any alternative
to this method?

When returning from main(), EXIT_SUCCESS and EXIT_FAILURE are generally the way to go. Since you're using C++, keep in mind that within your app, returning a bool or int is not the only way to signal an error has occurred. Exceptions are a powerful and versatile system for dealing with error conditions, but can be overkill for dealing with simple errors.

- Mike

Where do you put the braces?

Link260024-May-03 16:55

Link2600

24-May-03 16:55

I have seen tons of reference books doing this. They
put the braces right after the function names or class
names. For example,

instead of doing this:

class Cat
{
// codes

};

they do this:

class Cat {

// codes

};

But obviously, the first one is much clear than the
second one and not likely to make mistakes too.
What do you thinks? Especially those real world
programmers, what is your habit and why?