Re: how do I tell if something is lvalue?

[Artur Skawina via Digitalmars-d-learn]

On 02/01/16 20:47, Meta via Digitalmars-d-learn wrote:
> On Monday, 1 February 2016 at 18:28:05 UTC, Artur Skawina wrote:
>> On 01/31/16 23:11, Steven Schveighoffer via Digitalmars-d-learn wrote:
>>> Thanks! I was surprised this is not straightforward.
>>
>>enum isLvalue(alias A) = is(typeof((ref _){}(A)));
> 
> That looks much nicer. It still needs work to properly handle functions with 
> non-empty argument lists.

Then it gets a bit long for a one-liner ;)

   enum isLvalue(A...) = is(typeof((ref _){}(A[0](A[1..$] || is(typeof((ref 
_){}(A[0])));

> Also, can alias parameters take runtime variables? I can't remember.

Yes.

> 
> struct S
> {
> int w(int n) { return 1; }
  ref int wl(int n) { return x; }
> }
> 
> static assert(isLvalue!(S.w));


   static assert(!isLvalue!(S.w, 1));
   static assert(isLvalue!(S.wl, 1));


artur

Re: how do I tell if something is lvalue?

[Artur Skawina via Digitalmars-d-learn]

On 02/01/16 21:42, Artur Skawina wrote:
> On 02/01/16 20:47, Meta via Digitalmars-d-learn wrote:
>> That looks much nicer. It still needs work to properly handle functions with 
>> non-empty argument lists.
> 
> Then it gets a bit long for a one-liner ;)
> 
>enum isLvalue(A...) = is(typeof((ref _){}(A[0](A[1..$] || 
> is(typeof((ref _){}(A[0])));

And it's of course wrong in case there is a zero-args ref-returning
overload present. So...

   enum isLvalue(A...) = A.length>1?is(typeof((ref 
_){}(A[0](A[1..$]:is(typeof((ref _){}(A[0])));


artur

Re: Octree implementation?

[Benjamin Thaut via Digitalmars-d-learn]

On Monday, 1 February 2016 at 02:56:06 UTC, Tofu Ninja wrote:
Just out of curiosity, does anyone have an octree 
implementation for D laying around? Just looking to save some 
time.


https://github.com/Ingrater/thBase/blob/master/src/thBase/container/octree.d

Its a loose octree implementation. That means the cells overlap a 
bit to accomondate for the problem of objects that are on the 
border between to cells. I don't know though if you can rip out 
the implementation without some modifications.


Kind Regards
Benjamin Thaut

Re: how do I tell if something is lvalue?

[Meta via Digitalmars-d-learn]

On Monday, 1 February 2016 at 18:28:05 UTC, Artur Skawina wrote:
On 01/31/16 23:11, Steven Schveighoffer via Digitalmars-d-learn 
wrote:

Thanks! I was surprised this is not straightforward.


   enum isLvalue(alias A) = is(typeof((ref _){}(A)));

artur


That looks much nicer. It still needs work to properly handle 
functions with non-empty argument lists. Also, can alias 
parameters take runtime variables? I can't remember.


struct S
{
int w(int n) { return 1; }
}

static assert(isLvalue!(S.w));

Containers with non copyable types

[maik klein via Digitalmars-d-learn]

For example it is no problem in C++ to have

std::vector vuf;

But how can this be expressed in D?

For example

Array!(Unique!int) ua;

doesn't compile because it requires this(this) which is obviously 
disabled for "Unique".

Re: Region allocator strage error

[mark_mcs via Digitalmars-d-learn]

On Monday, 1 February 2016 at 12:05:53 UTC, ref2401 wrote:

On Sunday, 31 January 2016 at 14:48:34 UTC, ref2401 wrote:
I am getting runtime error: 
core.exception.AssertError@std\experimental\allocator\building_blocks\region.d(235): Assertion failure


At least tell me can anyone replicate it?


Reproduced on Windows 7 Pro x64 and Windows 10 Pro x64, DMD 2.070 
and 2.069.2. I don't have any 32-bit machines to test. I'll try 
and debug later.

Re: how do I tell if something is lvalue?

[Steven Schveighoffer via Digitalmars-d-learn]

On 2/1/16 2:47 PM, Meta wrote:

On Monday, 1 February 2016 at 18:28:05 UTC, Artur Skawina wrote:

On 01/31/16 23:11, Steven Schveighoffer via Digitalmars-d-learn wrote:

Thanks! I was surprised this is not straightforward.


   enum isLvalue(alias A) = is(typeof((ref _){}(A)));

artur


That looks much nicer. It still needs work to properly handle functions
with non-empty argument lists. Also, can alias parameters take runtime
variables? I can't remember.

struct S
{
 int w(int n) { return 1; }
}

static assert(isLvalue!(S.w));


Nice for the general case, but in my case, I don't need to worry about 
parameters.


Thanks!

-Steve

Re: chain(const(array of class)) fails

[SimonN via Digitalmars-d-learn]

Sorry for late reply -- but I got around to test a couple more 
cases!


On Monday, 1 February 2016 at 00:19:44 UTC, Nicholas Wilson wrote:

Unqaul means remove any const or immutable torn the type


Okay, that sounds like our 'const' shouldn't matter. 'const' is 
the outermost qualifier, and stripping that leaves us with B[] 
and C[], which were chainable earlier.



StaticMap is like a compile time map
What this error message says is that there is one candidate 
function that matches what you are attempting to do. and that 
chain takes a variadic argument and each of those arguments must
1) when unqualified be an input range (Basically you can 
foreach over it)


Yep, const(B[]) and const(C[]) can be foreached. My workaround 
has been to replace chain() with several foreaches.


2) that the common type of the element type of the unqualified 
variadic argument types is not void (in this case not arrays of 
void)
Have you tried changing The declaration of a and b to 
const(A[])?


Surprisingly, this compiles and gives the desired output:

const(B[]) b = [ new B(), new B() ];
const(A[]) c = [ new C(), new C() ]; // A instead of C

chain(b, c).each!(a => a.val.writeln);

With two arguments, const(array) has worked iff at least one 
range is of the base type. Only if none were of the base type, I 
got the error.


Apparently, the template is smart enough to infer the common base 
type without 'const', but needs to be fed the basetype in case of 
'const'.


My gut feeling is that I should report this as a bug against 
phobos...


Also have you tried with other reference type (e.g. assoc 
arrays pointers)?


immutable(B[int]) b;
immutable(C[int]) c;

chain(b.byValue, c.byValue).each!(a => a.val.writeln);

Error is the same as for the classes:

template std.range.chain cannot deduce function
from argument types !()(Result, Result), candidates are: /* 
snip */


To get this error, again, if at least one range is 
'immutable(A[int]).byValue', i.e., using the base class A, the 
template instantiates with no problems.


-- Simon

Re: how do I tell if something is lvalue?

[Meta via Digitalmars-d-learn]

On Monday, 1 February 2016 at 20:53:35 UTC, Artur Skawina wrote:

On 02/01/16 21:42, Artur Skawina wrote:

On 02/01/16 20:47, Meta via Digitalmars-d-learn wrote:
That looks much nicer. It still needs work to properly handle 
functions with non-empty argument lists.


Then it gets a bit long for a one-liner ;)

   enum isLvalue(A...) = is(typeof((ref _){}(A[0](A[1..$] 
|| is(typeof((ref _){}(A[0])));


And it's of course wrong in case there is a zero-args 
ref-returning overload present. So...


   enum isLvalue(A...) = A.length>1?is(typeof((ref 
_){}(A[0](A[1..$]:is(typeof((ref _){}(A[0])));



artur


Hmm, I think it can be simplified by replacing `A[0](A[1..$])` 
with `A(Parameters!A.init)`. Then the whole thing becomes:


enum isLvalue(alias A) = is(typeof((ref _) {} 
(A(Parameters!A.init;



*However*, we then run into this problem:

int n;

ref int returnN(int, float, bool) { return n; }
ref int returnN() { return n; }

static assert(isLvalue!returnN);


If I remember correctly this will just check the first returnN 
declaration.

How would you implement this in D? (signals & slots)

[Enjoys Math via Digitalmars-d-learn]

module signals_and_slots;

import std.algorithm: remove;

struct Slots(DelegateType, ArgTypes...) {
this() {

}

// How would you implement this?
void call(ArgTypes args) {
foreach (dg; delegates)
dg(args);
}

void connect(DelegateType slot) {
foreach (dg; delegates) {
if (dg == slot)
return;
}
delegates ~= slot;
}

void disconnect(DelegateType slot) {
for (uint k=0; k < delegates.length; k++) {
if (delegates[k] == slot)
delegates = delegates.remove(k);
}
}

private:
DelegateType[] delegates;
}

=

How do you implement this template called like:
void onColorChange(in Color) {
   // do something with color
}
auto slots = Slots!(void delegate(in Color), Color);
slots.connect();
auto color = Color(0.0, 1.0, 1.0, 1.0);
slots.call(color);

?

Thank you!

Re: How would you implement this in D? (signals & slots)

[Enjoys Math via Digitalmars-d-learn]

On Monday, 1 February 2016 at 21:40:45 UTC, Enjoys Math wrote:

module signals_and_slots;

import std.algorithm: remove;

[...]



D's signals & slots:

https://dlang.org/phobos/std_signals.html

Re: Region allocator strage error

[mark_mcs via Digitalmars-d-learn]

On Monday, 1 February 2016 at 12:05:53 UTC, ref2401 wrote:

On Sunday, 31 January 2016 at 14:48:34 UTC, ref2401 wrote:
I am getting runtime error: 
core.exception.AssertError@std\experimental\allocator\building_blocks\region.d(235): Assertion failure


At least tell me can anyone replicate it?


https://issues.dlang.org/show_bug.cgi?id=15637

(Sorry for the *triple* post).

Re: how do I tell if something is lvalue?

[tsbockman via Digitalmars-d-learn]

On Sunday, 31 January 2016 at 22:11:45 UTC, Steven Schveighoffer 
wrote:

Thanks! I was surprised this is not straightforward.

-Steve


For function return values, at least, you can do this:

import std.traits, std.stdio;

int foo()
{
return 0;
}

ref int bar()
{
static int x = 0;
return x;
}

enum isRetByRef(alias func) = (functionAttributes!func & 
FunctionAttribute.ref_) != 0;


void main()
{
writeln("foo: ", isRetByRef!foo);
writeln("bar: ", isRetByRef!bar);
}

(DPaste: http://dpaste.dzfl.pl/2aa8d3553a12)

Re: how do I tell if something is lvalue?

[Steven Schveighoffer via Digitalmars-d-learn]

On 2/1/16 5:20 PM, tsbockman wrote:

On Sunday, 31 January 2016 at 22:11:45 UTC, Steven Schveighoffer wrote:

Thanks! I was surprised this is not straightforward.

-Steve


For function return values, at least, you can do this:

import std.traits, std.stdio;

int foo()
{
 return 0;
}

ref int bar()
{
 static int x = 0;
 return x;
}

enum isRetByRef(alias func) = (functionAttributes!func &
FunctionAttribute.ref_) != 0;

void main()
{
 writeln("foo: ", isRetByRef!foo);
 writeln("bar: ", isRetByRef!bar);
}

(DPaste: http://dpaste.dzfl.pl/2aa8d3553a12)


Thanks. In my case, I need to treat fields and properties that return by 
ref the same way.


What I wanted essentially was a template constraint that says "this type 
has a member named foo, and t.foo is an lvalue"


-Steve

How do you get system time in specified precision?

[Enjoys Math via Digitalmars-d-learn]

That is in metric system units?

Ie milli-, micro-, hectanano-, nano-seconds?

The documentation doesn't show this well and many things are 
deprecated.


Please show me how!

Thank you.

Re: How do you get system time in specified precision?

[Steven Schveighoffer via Digitalmars-d-learn]

On 2/1/16 8:17 PM, Enjoys Math wrote:

That is in metric system units?

Ie milli-, micro-, hectanano-, nano-seconds?


Those are available from SysTime.fracSecs.

Is that what you are looking for? If not, please be more specific. time 
has a lot of different meanings.


-Steve

D with DerelictASSIMP3 question

[WhatMeWorry via Digitalmars-d-learn]

I'm porting a C++/opengl/AssImp tutorial over to 
D/DerelictOpenGL/DerelictAssImp

but have hit a brick wall.

It's a fairly large project but a tiny fragment suffices:

if(mesh.mMaterialIndex >= 0)
{
const aiMaterial* material = 
scene.mMaterials[mesh.mMaterialIndex];
// uint texCount = 
material.GetTextureCount(aiTextureType_SPECULAR);



Everything compiles fine.


But when I uncomment the call to GetTextureCount(), the Visual 
Studio D compiler comes back with:


ModelClass.d(165): Error: no property 'GetTextureCount' for type 
'const(aiMaterial*)'


I looked at AssImp documentation at

http://assimp.sourceforge.net/lib_html/structai_material.html

And it shows

unsigned intGetTextureCount (aiTextureType type) const
Get the number of textures for a particular texture type.

So it seems like such a simple error, but I've been stuck for 
days. Any suggestions?

Re: C Macro deeper meaning?

[Kagamin via Digitalmars-d-learn]

On Sunday, 31 January 2016 at 02:58:28 UTC, Andrew Edwards wrote:

void notUsed(T)(T v) { return cast(void)0; };

since it always returns cast(void)0 regardless of the input.

But it cannot be that simple, so what am I missing?


Now notUsed has an unused parameter v.

Re: How to set array length for multidimensional static arrays

[Jonathan M Davis via Digitalmars-d-learn]

On Monday, February 01, 2016 07:42:56 Namal via Digitalmars-d-learn wrote:
> On Monday, 1 February 2016 at 07:41:33 UTC, Namal wrote:
> > I understand that I cannot pass a variable to the static array
> > like in C++, and have to use dynamic arrays. But how can I set
> > the length for them without using a loop?
>
> I mean std::vector in C++, not array.

I'm not sure what you're trying to do exactly. static arrays cannot be
resized. They're a fixed size that's known at compile time. And they're
nothing like std::vector at all. e.g.

   int[42] arr;

That array has 42 elements and will always have 42 elements. And you can't
do something like

int[x] arr;

unless x is known at compile time (e.g. it's an enum).

Now, if you want something like std::vector, what you're probably looking
for is either dynamic arrays or std.container.Array. And dynamic arrays can
be allocated pretty much just like you'd do an array in C++ or Java. e.g.

auto arr = new int[](42);

Or you can set its length directly. e.g.

arr.length = 42;

If the new length is shorter than the current length, then it would be
identical to slicing the array and reassigning it to the original. e.g.

arr = arr[0 .. 42];

And if the new length is longer, then each of the new elements is set to the
init value of the of the element type.

Or you can append elements with ~=, which would be like using push_back.
e.g.

arr ~= 12;

And if you want to reserve a particular capacity for the dynamic array like
you might do with std::vector, then just use reserve. e.g.

arr.reserve(42);

If you haven't yet, you really should read this article:

http://dlang.org/d-array-article.html

It really should help you understand dynamic arrays in D.

However, be warned that its terminology is a bit off. It uses the term
dynamic array for the GC-managed block of memory that a typical dynamic
array refers to (per the language spec, T[] is a dynamic array regardless of
what kind of memory it refers to, and a GC-managed block of memory has no
official term). Similarly, it uses the term slice for T[] rather than
dynamic array, and while a non-null dynamic array is a slice of memory of
some kind, the term slice is used for a lot more in D than just arrays.
Still, while its terminology is a bit wrong, the article is very good and
really a must read for anyone who wants to understand dynamic arrays in D.

- Jonathan M Davis

Re: Region allocator strage error

[Marc Schütz via Digitalmars-d-learn]

On Monday, 1 February 2016 at 12:05:53 UTC, ref2401 wrote:

On Sunday, 31 January 2016 at 14:48:34 UTC, ref2401 wrote:
I am getting runtime error: 
core.exception.AssertError@std\experimental\allocator\building_blocks\region.d(235): Assertion failure


At least tell me can anyone replicate it?


Missing imports for c:
import std.experimental.allocator;
import std.experimental.allocator.building_blocks;

I can't reproduce it on Linux x86_64, neither with latest DMD 
from git, nor DMD 2.070.0.


It's the following assert, maybe it helps finding the cause:
https://github.com/D-Programming-Language/phobos/blob/master/std/experimental/allocator/building_blocks/region.d#L235

Re: how do I tell if something is lvalue?

[Steven Schveighoffer via Digitalmars-d-learn]

On 1/31/16 5:12 PM, Meta wrote:

On Sunday, 31 January 2016 at 22:11:45 UTC, Steven Schveighoffer wrote:

On 1/31/16 4:48 PM, Meta wrote:



This seems to do the trick, although I haven't extensively tested it.
There's probably a simpler way but this is the first thing I could come
up with that works.




Thanks! I was surprised this is not straightforward.



It seems to me like it would be a useful addition to __traits.


Yeah, the compiler probably has this handy.

https://issues.dlang.org/show_bug.cgi?id=15634

-Steve

Re: How to set array length for multidimensional static arrays

[Namal via Digitalmars-d-learn]

Sorry guys that I didn't express myself well. I also mixed some 
stuff up. What I wanted to ask is this, in c++ this is valid


int x = 3;
int y = 10;
int arr [x][y];

x,y are known at the compile time and arr is a static array. I 
can't do that in D so what is the best way to declare an array of 
that size?

Re: How to set array length for multidimensional static arrays

[Daniel Kozak via Digitalmars-d-learn]

V Mon, 01 Feb 2016 12:19:10 +
Namal via Digitalmars-d-learn 
napsáno:

> On Monday, 1 February 2016 at 12:12:00 UTC, Jonathan M Davis 
> wrote:
> > On Monday, February 01, 2016 11:15:40 Namal via 
> > Digitalmars-d-learn wrote:  
> >> Sorry guys that I didn't express myself well. I also mixed 
> >> some stuff up. What I wanted to ask is this, in c++ this is 
> >> valid
> >>
> >>   int x = 3;
> >>   int y = 10;
> >>   int arr [x][y];
> >>
> >> x,y are known at the compile time and arr is a static array. I 
> >> can't do that in D so what is the best way to declare an array 
> >> of that size?  
> >
> > If x and y are known at compile time, then you can declare a 
> > static array using them for dimensions. e.g.
> >
> > enum x = 3;
> > enum y = 10;
> > int[y][x] arr;
> >
> > But x and y must be something that it is evaluated by the 
> > compiler at compile time - e.g. an enum or a static variable. A 
> > local variable that just so happens to be directly initialized 
> > (like in your example) won't work.
> >
> > If x and y are _not_ known at compile time, then you can't use 
> > the to declare a static array. You'll have to use a dynamic 
> > array. e.g.
> >
> > auto arr = new int[][](x, y);
> >
> > - Jonathan M Davis  
> 
> Thanks alot, I didn't know that way with new.

you can use this too:
auto arr = new int[y][x];

Re: How to set array length for multidimensional static arrays

[Daniel Kozak via Digitalmars-d-learn]

V Mon, 01 Feb 2016 11:15:40 +
Namal via Digitalmars-d-learn 
napsáno:

> Sorry guys that I didn't express myself well. I also mixed some 
> stuff up. What I wanted to ask is this, in c++ this is valid
> 
>   int x = 3;
>   int y = 10;
>   int arr [x][y];
> 
> x,y are known at the compile time and arr is a static array. I 
> can't do that in D so what is the best way to declare an array of 
> that size?

You can do that:
immutable x = 3;
immutable y = 10;
int[y][x] arr;

Re: How to set array length for multidimensional static arrays

[Jonathan M Davis via Digitalmars-d-learn]

On Monday, February 01, 2016 11:15:40 Namal via Digitalmars-d-learn wrote:
> Sorry guys that I didn't express myself well. I also mixed some
> stuff up. What I wanted to ask is this, in c++ this is valid
>
>   int x = 3;
>   int y = 10;
>   int arr [x][y];
>
> x,y are known at the compile time and arr is a static array. I
> can't do that in D so what is the best way to declare an array of
> that size?

If x and y are known at compile time, then you can declare a static array
using them for dimensions. e.g.

enum x = 3;
enum y = 10;
int[y][x] arr;

But x and y must be something that it is evaluated by the compiler at
compile time - e.g. an enum or a static variable. A local variable that just
so happens to be directly initialized (like in your example) won't work.

If x and y are _not_ known at compile time, then you can't use the to
declare a static array. You'll have to use a dynamic array. e.g.

auto arr = new int[][](x, y);

- Jonathan M Davis

Re: Region allocator strage error

[ref2401 via Digitalmars-d-learn]

On Sunday, 31 January 2016 at 14:48:34 UTC, ref2401 wrote:
I am getting runtime error: 
core.exception.AssertError@std\experimental\allocator\building_blocks\region.d(235): Assertion failure


At least tell me can anyone replicate it?

Re: How to set array length for multidimensional static arrays

[Namal via Digitalmars-d-learn]

On Monday, 1 February 2016 at 12:12:00 UTC, Jonathan M Davis 
wrote:
On Monday, February 01, 2016 11:15:40 Namal via 
Digitalmars-d-learn wrote:
Sorry guys that I didn't express myself well. I also mixed 
some stuff up. What I wanted to ask is this, in c++ this is 
valid


  int x = 3;
  int y = 10;
  int arr [x][y];

x,y are known at the compile time and arr is a static array. I 
can't do that in D so what is the best way to declare an array 
of that size?


If x and y are known at compile time, then you can declare a 
static array using them for dimensions. e.g.


enum x = 3;
enum y = 10;
int[y][x] arr;

But x and y must be something that it is evaluated by the 
compiler at compile time - e.g. an enum or a static variable. A 
local variable that just so happens to be directly initialized 
(like in your example) won't work.


If x and y are _not_ known at compile time, then you can't use 
the to declare a static array. You'll have to use a dynamic 
array. e.g.


auto arr = new int[][](x, y);

- Jonathan M Davis


Thanks alot, I didn't know that way with new.

Determine type of property

[Steven Schveighoffer via Digitalmars-d-learn]

S has 3 different properties, x, y, z:

struct S
{
   int x;
   int y() { return 1;}
}

int z(S s) { return 1;}

pragma(msg, typeof(S.init.x).stringof); // int
pragma(msg, typeof(S.init.y).stringof); // int()
pragma(msg, typeof(S.init.z).stringof); // int

Is there a trait I can call/use to consistently get "int" from all 3?

-Steve

Re: how do I tell if something is lvalue?

[tsbockman via Digitalmars-d-learn]

On Monday, 1 February 2016 at 22:32:26 UTC, Steven Schveighoffer 
wrote:
What I wanted essentially was a template constraint that says 
"this type has a member named foo, and t.foo is an lvalue"


-Steve


Like this?

template hasLValProperty(T, string property) {
enum hasLValProperty = __traits(compiles, function(ref T x) {
void requireLVal(V)(ref V y) { }
requireLVal(mixin("x." ~ property));
});
}

struct Foo {
int a;
}
struct Bar {
int b() {
return 0; }
}
struct Baz {
ref int c() {
static int _c;
return _c;
}
}

void test(T, string property)() {
import std.stdio;
write(T.stringof, ".", property, " is ");
if(!hasLValProperty!(T, property))
write("NOT ");
writeln("an lvalue");
}

void main() {
import std.stdio;

test!(Foo, "a")();
test!(Foo, "b")();
test!(Bar, "a")();
test!(Bar, "b")();
test!(Baz, "c")();
}

(DPaste: http://dpaste.dzfl.pl/5877cc17ffd2)

Re: Determine type of property

[tsbockman via Digitalmars-d-learn]

On Tuesday, 2 February 2016 at 03:36:25 UTC, Steven Schveighoffer 
wrote:

S has 3 different properties, x, y, z:

struct S
{
   int x;
   int y() { return 1;}
}

int z(S s) { return 1;}

pragma(msg, typeof(S.init.x).stringof); // int
pragma(msg, typeof(S.init.y).stringof); // int()
pragma(msg, typeof(S.init.z).stringof); // int

Is there a trait I can call/use to consistently get "int" from 
all 3?


-Steve


import std.traits, std.stdio;

alias PropertyType(T, string property) =
ReturnType!(function(T x) { return mixin("x." ~ property); });

struct S
{
   int x;
   int y() { return 1;}
}

int z(S s) { return 1;}

void main() {
writeln(PropertyType!(S, "x").stringof);
writeln(PropertyType!(S, "y").stringof);
writeln(PropertyType!(S, "z").stringof);
}

(DPaste: http://dpaste.dzfl.pl/0b03bc8ea11f)

How do you do a typeid(obj) to get the most derived class that it is, or string?

[Enjoys Math via Digitalmars-d-learn]

class A {

}

class B : A {

}

class C : B {

}

auto b = new B();

typeid(b) == "B"

?

Thanks.

Re: D with DerelictASSIMP3 question

[Maeriden via Digitalmars-d-learn]

On Tuesday, 2 February 2016 at 02:57:14 UTC, WhatMeWorry wrote:
I'm porting a C++/opengl/AssImp tutorial over to 
D/DerelictOpenGL/DerelictAssImp

but have hit a brick wall.

[...]


Try aiGetMaterialTextureCount.
I'm guessing derelict uses the C API as much as it can.

Re: D with DerelictASSIMP3 question

[Mike Parker via Digitalmars-d-learn]

On Tuesday, 2 February 2016 at 03:22:16 UTC, Maeriden wrote:


Try aiGetMaterialTextureCount.
I'm guessing derelict uses the C API as much as it can.


It uses the C API exclusively.

Re: How to set array length for multidimensional static arrays

[Jonathan M Davis via Digitalmars-d-learn]

On Monday, February 01, 2016 13:22:23 Daniel Kozak via Digitalmars-d-learn 
wrote:
> V Mon, 01 Feb 2016 12:19:10 +
> Namal via Digitalmars-d-learn 
> napsáno:
>
> > On Monday, 1 February 2016 at 12:12:00 UTC, Jonathan M Davis
> > wrote:
> > > On Monday, February 01, 2016 11:15:40 Namal via
> > > Digitalmars-d-learn wrote:
> > >> Sorry guys that I didn't express myself well. I also mixed
> > >> some stuff up. What I wanted to ask is this, in c++ this is
> > >> valid
> > >>
> > >>   int x = 3;
> > >>   int y = 10;
> > >>   int arr [x][y];
> > >>
> > >> x,y are known at the compile time and arr is a static array. I
> > >> can't do that in D so what is the best way to declare an array
> > >> of that size?
> > >
> > > If x and y are known at compile time, then you can declare a
> > > static array using them for dimensions. e.g.
> > >
> > > enum x = 3;
> > > enum y = 10;
> > > int[y][x] arr;
> > >
> > > But x and y must be something that it is evaluated by the
> > > compiler at compile time - e.g. an enum or a static variable. A
> > > local variable that just so happens to be directly initialized
> > > (like in your example) won't work.
> > >
> > > If x and y are _not_ known at compile time, then you can't use
> > > the to declare a static array. You'll have to use a dynamic
> > > array. e.g.
> > >
> > > auto arr = new int[][](x, y);
> > >
> > > - Jonathan M Davis
> >
> > Thanks alot, I didn't know that way with new.
>
> you can use this too:
> auto arr = new int[y][x];

True, but that's not the same thing. It creates a dynamic array of static
arrays instead of a static array of dynamic arrays. e.g.

auto a = new int[][](5, 10);
auto b = new int[5][10];
auto c = new int[5][](10);
writeln(typeof(a).stringof);
writeln(typeof(b).stringof);
writeln(typeof(c).stringof);

prints

int[][]
int[5][]
int[5][]

And in the cases where the inner element is a static array, its length has
to be known compile time, whereas the lengths of the dynamic arrays don't.

On a side note, I really wish that putting the size inside of the brackets
was illegal for dynamic arrays to make what's going on clearer, but instead,
the outer layer can go either in the brackets or in the parens, whereas
where the other layers go changes them between dynamic arrays and static
arrays.

- Jonathan M Davis

Re: how do I tell if something is lvalue?

[Artur Skawina via Digitalmars-d-learn]

On 01/31/16 23:11, Steven Schveighoffer via Digitalmars-d-learn wrote:
> Thanks! I was surprised this is not straightforward.

   enum isLvalue(alias A) = is(typeof((ref _){}(A)));

artur