Re: Efficient way to pass struct as parameter
On Tuesday, 2 January 2018 at 22:49:20 UTC, Adam D. Ruppe wrote: On Tuesday, 2 January 2018 at 22:17:14 UTC, Johan Engelen wrote: Pass the Vector3f by value. This is very frequently the correct answer to these questions! Never assume ref is faster if speed matters - it may not be. However speed really matters for me. I am writing a path tracing program. Ray will be constructed million of times during computation. And will be passed to functions to test intersection billion of times. After Reading comments here, it seems ray will be passed by value to the intersection testing function. I am not sure if ray is small enough to be passed by value. It needs some experiment.
Efficient way to pass struct as parameter
I am creating Vector3 structure. I use struct to avoid GC.
However, struct will be copied when passed as parameter to
function
struct Ray {
Vector3f origin;
Vector3f dir;
@nogc @system
this(Vector3f *origin, Vector3f *dir) {
this.origin = *origin;
this.dir = *dir;
}
}
How can I pass struct more efficiently?
Re: Avoiding GC in D and code consistancy
On Sunday, 31 December 2017 at 07:32:50 UTC, Ali Çehreli wrote:
On 12/30/2017 11:16 PM, Tim Hsu wrote:
> Struct version of Vector3f can't derive toString
> method. writeln() prints unformated struct members. I know I
can use
> helper function here. But is there any other way?
The normal way that I know is to insert a function like the
following into Vector3f:
string toString() {
import std.string : format;
return format("%s,%s,%s", x, y, z);
}
> class version of Vector3f. Require new operator in
opBinary(). scoped!
> won't work here.
>
> Is there a better to write vector3f class while avoiding GC?
Yeah, it doesn't make sense that a type of x, y, z should be a
class. I would stay with a struct here.
Ali
Sorry I am a bit disappointed. It seems writeln itself will check
if the struct to be printed has toString. If not, it use default
struct printer.
Avoiding GC in D and code consistancy
I came from C++ looking forward to D. Some languages require
programmers to use GC all the time. However, A lot of time we
don't really need GC especially when the time of destruction is
deterministic in compile time.
I found that struct in D is allocate on stack by default. And we
can use scope! to allocate class on stack too.
See the following code. Struct version of Vector3f can't derive
toString method. writeln() prints unformated struct members. I
know I can use helper function here. But is there any other way?
struct Vector3f {
public:
this(float x, float y, float z) {
this.x = x;
this.y = y;
this.z = z;
}
@property float length2() {
return x*x+y*y+z*z;
}
@property float length() {
import std.math;
return sqrt(x*x+y*y+z*z);
}
Vector3f opBinary(string op)(Vector3f rhs)
{
static if (op == "+") return Vector3f(x+rhs.x, y+rhs.y,
z+rhs.z);
else static if (op == "-") return Vector3f(x-rhs.x,
y-rhs.y, z-rhs.z);
else static assert(0, "Operator "~op~" not implemented");
}
float x, y, z;
}
class version of Vector3f. Require new operator in opBinary().
scoped! won't work here.
Is there a better to write vector3f class while avoiding GC?
glfwSetDropCallback undefined symbol
DCD and DMD says that the symbol is undefined! However, I look into derelichtGLFW3. It has this symbol defined! It looks like a bug for me!
Re: Passing this to void *
On Wednesday, 22 November 2017 at 15:36:22 UTC, Adam D. Ruppe
wrote:
On Wednesday, 22 November 2017 at 15:31:36 UTC, Tim Hsu wrote:
It seems in D, reference has its own address, am I right?
unlike c++
The local variable does have its own address. Do not take its
address - avoid or
Just cast the ref itself.
In D, a class this or Object variable is already like a C++
Foo*. If you & that, you get a Foo** - not what you want in
most cases.
Thanks after doing some experiment I guess I finally understand
class App {
@property void *ptr() {
return cast(void *)(this);
}
}
void printaddr(void *ptr)
{
writeln(ptr);
}
void main()
{
Pizza pza = new Pizza("XD");
Pizza pza2 = pza;
printaddr(pza.ptr);
printaddr(pza2.ptr);
printaddr();
printaddr();
}
Result:
A32000
A32000
19FDB0
19FDB4
Conclusion:
pza and pza2 is two different reference variable refer to same
new-ed object.
Re: Passing this to void *
On Wednesday, 22 November 2017 at 15:27:27 UTC, Dukc wrote: On Wednesday, 22 November 2017 at 15:17:33 UTC, Adam D. Ruppe wrote: On Wednesday, 22 November 2017 at 15:07:54 UTC, Stefan Koch wrote: will do. Even if it were an lvalue, that would be the address of a local. You should basically NEVER do that with D classes. Just `cast(void*) this` if you must pass it to such a function. It's worth noting that you will still be passing different addresses to foo(void*) because classes are reference types in D (structs are not). In the constructor you're passing the address of the class object itself, but in the main function you're passing the address of the reference. It seems in D, reference has its own address, am I right? unlike c++
Re: Passing this to void *
On Wednesday, 22 November 2017 at 15:17:33 UTC, Adam D. Ruppe
wrote:
On Wednesday, 22 November 2017 at 15:07:54 UTC, Stefan Koch
wrote:
will do.
Even if it were an lvalue, that would be the address of a
local. You should basically NEVER do that with D classes.
Just `cast(void*) this` if you must pass it to such a function.
I am afraid what will happen when casting this reference to void *
glfwSetWindowUserPointer gives us a chance to provide a pointer
to userdata. so that in callback function, we can retrieve the
data and don't have to declare global variable.
class App {
public this() {
m_window = glfwCreateWindow();
glfwSetWindowUserPointer(m_window, cast(void *)());
}
}
How do I use this function in Dlang?
sorry for my bad english.
Re: Passing this to void *
On Wednesday, 22 November 2017 at 15:14:32 UTC, Stefan Koch wrote: On Wednesday, 22 November 2017 at 15:11:08 UTC, Tim Hsu wrote: On Wednesday, 22 November 2017 at 15:07:54 UTC, Stefan Koch will do. I've tried it in the first place. ... Error: this is not an lvalue In that case casting to void* should be fine. But..The compiler still does not produce the executable... foo(); app.d(17): Error: this is not an lvalue
Re: Passing this to void *
On Wednesday, 22 November 2017 at 15:07:54 UTC, Stefan Koch wrote:
On Wednesday, 22 November 2017 at 15:07:08 UTC, Tim Hsu wrote:
I am a C++ game developer and I want to give it a try.
It seems "this" in Dlang is a reference instead of pointer.
How can I pass it as void *?
void foo(void *);
class Pizza {
public:
this() {
Pizza newone = this;
// works but newone is actually not this pizza.
foo();
// this does not work..
foo(this);
}
}
void main() {
Pizza pizza = new Pizza();
// this works...
foo();
}
will do.
I've tried it in the first place.
...
Error: this is not an lvalue
Passing this to void *
I am a C++ game developer and I want to give it a try.
It seems "this" in Dlang is a reference instead of pointer.
How can I pass it as void *?
void foo(void *);
class Pizza {
public:
this() {
Pizza newone = this;
// works but newone is actually not this pizza.
foo();
// this does not work..
foo(this);
}
}
void main() {
Pizza pizza = new Pizza();
// this works...
foo();
}
