Re: passing a string to a dll
On Wed, 19 Sep 2007 03:58:58 GMT, "David Ching" <dc@remove-this.dcsoft.com>
wrote:
Well, my point is David We. inadvertently got it wrong by saying
if (s.Compare(_T("12345")) ) was the same as
if (s == (_T("12345"))
when in fact they mean the opposite,
and to use the Compare() method, you actually have to say "!s.Compare()" or
else say "== 0" which illustrates how confusing is the stupid C convention
of having something equal to 0 actually means it is true.
It's hardly "a convention"[*], and CString::Compare is not even a boolean
function. (True C boolean functions such as isupper return non-zero for
"true" and 0 for "false".)
Using CString::operator == nicely gets around all of that.
The differences are:
1. operator== is boolean, while Compare is not.
2. operator== isn't useful for sorting, while Compare is.
To test for equality, the first thought should be operator==. I suppose the
second could be to look for a function named "Equals" or some variation on
that.
[*] I believe you're thinking more of the Unix convention of programs
returning 0 to indicate "completed without error". It makes some sense,
because there is only one such value, while there are many potential error
values, and it allows one to write idiomatic code such as:
int error = f();
if (error)
{
// handle error
}
When it is anticipated that the failure case is the one that requires
special handling, this does make some sense, but I still wouldn't do it
that way nowadays, because I think of "success" as "true" and "failure" as
"false". I like to keep that concept separate from error values, and there
is a lot to be said for doing things consistently.
--
Doug Harrison
Visual C++ MVP