Jeremie Pelletier wrote:
> Andrei Alexandrescu wrote:
>> Chris Nicholson-Sauls wrote:
>>> downs wrote:
>>>>
>>>> Here is a funny consequence of this amusing fact:
>>>>
>>>> if you overload opAssign in a struct with lazy T[] dgs..., you can
>>>> achieve the following syntax
>>>>
>>>>
>>>>> WithFlag(GL_BLEND, true) = WithDepthMask(false) = tex.With =
>>>>> Quads = {
>>>>> foreach (i, q; qa) {
>>>>> float f = 1f*i / qa.length; Color(1f-f, f, 1f);
>>>>> TexCoord(0f, 0f); Vertex(q.points[0]);
>>>>> TexCoord(1f, 0f); Vertex(q.points[1]);
>>>>> TexCoord(1f, 1f); Vertex(q.points[3]);
>>>>> TexCoord(0f, 1f); Vertex(q.points[2]);
>>>>> }
>>>>> };
>>>
>>> That's... just beautiful...
>>>
>>> -- Chris Nicholson-Sauls
>>
>> Not getting it... could someone please explain?
>>
>> Andrei
>
> From what I get, he has something like this:
>
> struct WithFlag(int OP, bool enable) {
> static void opAssign(T)(lazy T next) {
> static if(enable) glEnable(OP);
> else glDisable(OP);
> next();
> }
> }
>
> struct WithDepthMask(bool enable) {
> static void opAssign(T)(lazy T next) {
> glDepthMask(enable);
> next();
> }
> }
>
> struct Tex {
> void opAssign(T)(lazy T next) {
> glBindTexture(_tex);
> next();
> }
> }
>
> struct Quads {
> static void opAssign(T)(lazy T commands) {
> glBegin(GL_QUADS);
> commands();
> glEnd();
> }
> }
>
> I don't know if thats his exact code, but from what I can remember of gl
> from memory it should look like this.
>
> Jeremie
Very close. There's another workaround required to enable the = {} syntax.
The T in question can either be a void, in which case we're assigning a
function call, or a void delegate(), in which case we're assigning a subscope.
Because the parameter is lazy, in the case of void delegate() we actually have
to call it doubly nestedly!
This leads to the following code.
> const string LazyCall="
> static if (is(T==void)) t();
> else static if (is(T==void delegate())) t()();
> else static assert(false, T.stringof);
> ";
...
> template PrimitiveScope(string NAME, string WHICH) {
> const string PrimitiveScope="struct "~NAME~" {
> static void opAssign(T)(lazy T t) {
> glBegin("~WHICH~"); scope(exit) glEnd();
> "~LazyCall~"
> }
> }";
> }
...
> mixin(Concat!(MAP!(PrimitiveScope, 2,
> "Points", "GL_POINTS", "Lines", "GL_LINES",
> "LineLoop", "GL_LINE_LOOP", "LineStrip", "GL_LINE_STRIP",
> "Triangles", "GL_TRIANGLES", "TriangleStrip", "GL_TRIANGLE_STRIP",
> "TriangleFan", "GL_TRIANGLE_FAN", "Quads", "GL_QUADS",
> "QuadStrip", "GL_QUAD_STRIP", "Polygon", "GL_POLYGON"
> )));
:deranged grin: I love templates!
