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#ActualHodgman

Posted 01 January 2013 - 08:25 AM

You could always write a "boxed type" template class that encapsulates a primitive type, while supporting the same operators the primitive type does. So, essentially reinventing Java's "boxed types" in C++ using templates. I'm not in a position to say whether that would be worth the effort, though. My guess would be that it isn't.
I have one of those in my engine, which acts like the type (operator wise), but with an explicit constructor from that type.
e.g. short version:
template<class T, class Tag> struct P
{
	P() : value() {}
	explicit P( T v ) : value(v) {}
	T value;
};
struct MetreTag {};
struct InchTag {};
typedef P<float, MetreTag> Metre;
typedef P<float, InchTag> Inch;
And then I write conversion functions like:
Inch ToInches(Metre m) { return Inch(m.value * 39.3700787f); }
void test()
{
	Metre m(10);
	Inch i( ToInches(m) );
	Inch error( m );//won't compile
}
I haven't used the boost solution, but I imagine it's similar to this, so I probably suffer from the same issues that SOTL found with boost's version.

#1Hodgman

Posted 01 January 2013 - 08:21 AM

You could always write a "boxed type" template class that encapsulates a primitive type, while supporting the same operators the primitive type does. So, essentially reinventing Java's "boxed types" in C++ using templates. I'm not in a position to say whether that would be worth the effort, though. My guess would be that it isn't.
I have one of those in my engine, which acts like the type (operator wise), but with an explicit constructor from that type.
e.g. short version:
template<class T, class Tag> struct P
{
	P() : value() {}
	explicit P( T v ) : value(v) {}
	T value;
};
struct MetreTag {};
struct InchTag {};
typedef P<float, MetreTag> Metre;
typedef P<float, InchTag> Inch;
And then I write conversion functions like:
Inch ToInches(Metre m) { return Inch(m.value * 39.3700787f); }
void test()
{
	Metre m(10);
	Inch i( ToInches(m) );
	Inch error( m );//won't compile
}

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