• Artyom Shalkhakov <artyom.shalkhakov gmail.com> Aug 03 2007
• Daniel Keep <daniel.keep.lists gmail.com> Aug 03 2007
• Artyom Shalkhakov <artyom.shalkhakov gmail.com> Aug 04 2007

Artyom Shalkhakov <artyom.shalkhakov gmail.com> writes:

I'm trying to do byte-order conversions in compile-time rather than run-time,
since the latter case is rarely needed (if needed at all).

/// byte-order conventions (for uint conversion)
enum BYTEORDER {
	ARGB8,
	ABGR8,
	RGBA8,
	BGRA8
}

/// color, represented as RGB triple
struct Col3 {
	static Col3 opCall( float r, float g, float b ) {
		...
	}

        // byte-order is mostly static, so I tried to do this using templates
	static Col3 opCall( BYTEORDER order )( uint rgb ) {
		Col3	dst;

		// unpack according to byte-order
		static if ( order == ARGB8 ) {
			...
		}
		else static if ( order == ABGR8 ) {
			...
		}
		....
	}

	float	r, g, b;
}

compiler says:
template Col3.opCall( BYTEORDER order ) conflicts with function Col3.opCall at
...

Why can't I do this? I had to make a parameter for opCall to be able to compile
it.
I'm using Tango 0.99 RC3 / DMD 1.18 on Windows.

Daniel Keep <daniel.keep.lists gmail.com> writes:

Artyom Shalkhakov wrote:
 I'm trying to do byte-order conversions in compile-time rather than run-time,
since the latter case is rarely needed (if needed at all).
 
 /// byte-order conventions (for uint conversion)
 enum BYTEORDER {
 	ARGB8,
 	ABGR8,
 	RGBA8,
 	BGRA8
 }
 
 /// color, represented as RGB triple
 struct Col3 {
 	static Col3 opCall( float r, float g, float b ) {
 		...
 	}
 
         // byte-order is mostly static, so I tried to do this using templates
 	static Col3 opCall( BYTEORDER order )( uint rgb ) {
 		Col3	dst;
 
 		// unpack according to byte-order
 		static if ( order == ARGB8 ) {
 			...
 		}
 		else static if ( order == ABGR8 ) {
 			...
 		}
 		....
 	}
 
 	float	r, g, b;
 }
 
 compiler says:
 template Col3.opCall( BYTEORDER order ) conflicts with function Col3.opCall at
...
 
 Why can't I do this? I had to make a parameter for opCall to be able to
compile it.
 I'm using Tango 0.99 RC3 / DMD 1.18 on Windows.


Because you have a template and a function with the same symbol name.
Let's remove the struct for a moment to get

static Col3 opCall(float r, float g, float b);
static Col3 opCall(BYTEORDER order)(uint rgb);

What the compiler sees this as is:

static Col3 opCall(float r, float g, float b);
template Col3(BYTEORDER order)
{
    static Col3(uint rgb);
}

That's like creating a class and a function with the same name: you
can't do it.  You also can't overload templated functions, at least not
directly.  You can make it work by turning the other function into a
template and making sure it has a different number of template arguments:

static Col3 opCall()(float r, float g, float b);
static Col3 opCall(BYTEORDER order)(uint rgb);

Note that the above isn't tested.  Also note that, last time I checked,
you can only have one templated member function with any given name, so
it might not work at all.

	-- Daniel

Artyom Shalkhakov <artyom.shalkhakov gmail.com> writes:

Daniel Keep Wrote:

(text omitted)

Thanks for pointing this one out to me. I'll try the way you described to see
if it works.