Re: Overloading on return value (with a trick)
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o_O
It seems that the moderation software already took care of the issue. ;)
jaybus56 wrote:
[overloading on the returnvalue]
I've read a lot of (pseudo) arguments why this fact is a must. (I
disagree with (almost) all of them (as far as I remember). Anyway: it
is like it is.)
Hmmm, the main issue is that you can choose to ignore the returnvalue,
leaving the compiler with no way to actually figure out which overload you
wanted.
That said, you _can_ have a function overloaded by the returntype and I
actually use that a lot. The simple solution is to have a template
parameter. Then, you you simply say it explicitly which overload you want:
int x = parse<int>(some_string);
float f = boost::lexical_cast<float>(another_string);
char* c = reinterpret_cast<char*>(42);
Okay, the last one is actually not an overloaded function, but I like the
similarity of the syntax.
struct TestFunky
{
int val;
char chr;
TestFunky( int v, char c)
: val(v)
, chr(c)
{}
};
class funky
{
TestFunky& tf_;
public:
funky(TestFunky& tf)
: tf_(tf)
{}
operator int()
{
return tf_.val;
}
operator char()
{
return tf_.chr;
}
};
TestFunky testy( 666, 'E');
// and so we do as we wanted to.
int i = funky(testy);
char c = funky(testy);
A bit complicated for my taste...
// .and it even doesn't need more CPU load! (If the compiler isn't too
dumb.)
Really? You first need both the 666 and the 'E', which are IIUC the results
of the two function calls, so typically one of them is wasted. That's also
why I'd use a less complicated one:
int int_function();
char char_function();
struct proxy {
operator int() const {
return int_function();
}
operator char() const {
return char_function();
}
};
proxy function() {
return proxy();
}
Here, you only have a single proxy object that call one of the functions on
demand, depending on which conversion is requested.
Of course
<.
funky(testy); // doesn't work
.>
The problem here is that the actual function isn't called (my code) or both
are called (your code). In some cases I can actually live with that or a
runtime error.
Uli
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