Re: anyway to set a const object after the fact?
On Monday, 29 October 2018 at 21:50:32 UTC, aliak wrote:
Hi, so if you have this piece of code:
struct C {
void f() {
string[] others;
const string[] restArgs;
foreach (i, arg; args) {
if (isValidArg(arg)) {
restArgs = args[i + 1 .. $];
break;
}
others ~= arg;
}
// "others" is a list of args before the valid arg is
encountered
// "restArgs" is a list that is the args after the valid arg
}
}
Is there anyway to set a const object after declaring it in the
above context?
Cheers,
- Ali
It looks like there is a Rebindable type for that in std.typecons
: https://dlang.org/phobos/std_typecons.html#Rebindable
Re: Built-in array opSliceAssign
On Thursday, 25 October 2018 at 21:00:46 UTC, Adam D. Ruppe wrote: On Thursday, 25 October 2018 at 19:56:18 UTC, Stanislav Blinov wrote: The current behavior of the compiler is quite the opposite of those "same as" above. Yeah, I guess I am maybe selectively reading the spec in light of the implementation... but I think the examples are just sloppy. Or maybe we have a buggy implementation but idk which is more useful. I still hold my believe that if opAssign is defined then that should be used. In my humble opinion, the current way might/could be faster, but it's not correct.
DirectX bindings
I want to do some graphics using direct3d11 on windows. There are some bindings that I used once before https://github.com/evilrat666/directx-d However they are marked as [discontinued] While I'm sure they will continue to work so wouldn't worry about using this I wonder if there are any other options?
Re: DirectX bindings
On Tuesday, 30 October 2018 at 10:30:48 UTC, John Burton wrote: I want to do some graphics using direct3d11 on windows. There are some bindings that I used once before https://github.com/evilrat666/directx-d However they are marked as [discontinued] While I'm sure they will continue to work so wouldn't worry about using this I wonder if there are any other options? https://code.dlang.org/packages/aurora-directx
Re: DirectX bindings
On Tuesday, 30 October 2018 at 10:46:35 UTC, Mike Parker wrote: On Tuesday, 30 October 2018 at 10:30:48 UTC, John Burton wrote: I want to do some graphics using direct3d11 on windows. There are some bindings that I used once before https://github.com/evilrat666/directx-d However they are marked as [discontinued] While I'm sure they will continue to work so wouldn't worry about using this I wonder if there are any other options? https://code.dlang.org/packages/aurora-directx Thank you, I don't know why my search of the repository didn't find this. I think I was searching for direct3d perhaps :)
Re: anyway to set a const object after the fact?
On Monday, 29 October 2018 at 22:12:24 UTC, Paul Backus wrote:
Use a lambda:
const string[] restArgs = () {
foreach(i, arg; args) {
if (isValidArg(arg)) {
return args[i+1 .. $];
}
others ~= arg;
}
}();
That works.
Re: anyway to set a const object after the fact?
On Tuesday, 30 October 2018 at 08:18:15 UTC, Laurent Tréguier
wrote:
On Monday, 29 October 2018 at 21:50:32 UTC, aliak wrote:
Hi, so if you have this piece of code:
struct C {
void f() {
string[] others;
const string[] restArgs;
foreach (i, arg; args) {
if (isValidArg(arg)) {
restArgs = args[i + 1 .. $];
break;
}
others ~= arg;
}
// "others" is a list of args before the valid arg is
encountered
// "restArgs" is a list that is the args after the valid
arg
}
}
Is there anyway to set a const object after declaring it in
the above context?
Cheers,
- Ali
It looks like there is a Rebindable type for that in
std.typecons :
https://dlang.org/phobos/std_typecons.html#Rebindable
Guess I could do that. But would there be a difference if I just
declared the restArgs as non const then? Given the objective is
"set this var to point to this thing and not allow it to be set
to point to anything else".
Re: anyway to set a const object after the fact?
On Monday, 29 October 2018 at 22:05:16 UTC, H. S. Teoh wrote:
What exactly are you trying to accomplish? I.e., what
semantics do you want from modifying restArgs?
Trying to set restArgs to point to some data but only set it
once. Would require some sort of control flow analysis on the
part of D though I guess. So meh.
If you're looking to rebind the array, just be a bit more
explicit in how you spell out the type:
const(string)[] restArgs;
will allow you to rebind it to a different array / slice, but
still not permit you to modify the array elements.
T
Ya, I was looking to bind once. Like what you can do this with a
module constructor:
const int a;
static this() {
a = 5;
}
Re: anyway to set a const object after the fact?
On Tuesday, 30 October 2018 at 11:23:48 UTC, aliak wrote: Guess I could do that. But would there be a difference if I just declared the restArgs as non const then? Given the objective is "set this var to point to this thing and not allow it to be set to point to anything else". The difference with const is that you wouldn't be able to modify the array itself (by adding or removing arguments for example). But yes, you can still re-assign it multiple times using Rebindable, so the lambda solution is a better idea indeed.
Re: Where do I learn to use GtkD
On Sunday, 13 March 2016 at 19:28:57 UTC, karabuta wrote: Gtk3 from python3 has got I nice book with examples that are not so advanced but enough to get you doing real work(from a beginner point of view). GtkD seem to have changed the API structure compared to python3 Gtk3 and the demo examples just "show-off" IMO :). The documentation is really^ not good :) Any help on where I can get better leaning materials(GtkD)? Repo, blogs post, etc please I will avoid using GTK for large projects. If can be used for simple things and you can automate a lot of acts(and use glade for UI design)... but it has some problems that will bite you in the long run. I'd just jump in to it, it's not too hard but hard to find the correct information. It will be a time investment of a few months. Might try nuklearD first. Seems to be better in many aspects.
Re: anyway to set a const object after the fact?
On Tuesday, October 30, 2018 2:18:15 AM MDT Laurent Tréguier via
Digitalmars-d-learn wrote:
> On Monday, 29 October 2018 at 21:50:32 UTC, aliak wrote:
> > Hi, so if you have this piece of code:
> >
> > struct C {
> >
> > void f() {
> >
> > string[] others;
> > const string[] restArgs;
> > foreach (i, arg; args) {
> >
> > if (isValidArg(arg)) {
> >
> > restArgs = args[i + 1 .. $];
> > break;
> >
> > }
> > others ~= arg;
> >
> > }
> > // "others" is a list of args before the valid arg is
> >
> > encountered
> >
> > // "restArgs" is a list that is the args after the valid arg
> >
> > }
> >
> > }
> >
> > Is there anyway to set a const object after declaring it in the
> > above context?
> >
> > Cheers,
> > - Ali
>
> It looks like there is a Rebindable type for that in std.typecons
>
> : https://dlang.org/phobos/std_typecons.html#Rebindable
Rebindable is specifically intentended for class references, since D doesn't
really distinguish between the reference and what it's pointing to, making
it impossible to under normal circumstances to have a mutable reference to a
const object. On the other hand, you can easily have mutable arrays of const
objects. Using Rebindable is a really a hack (albeit a very necessary one
for some circumstances), and I would very much advise _against_ using it if
you don't need it. Historically, it tends to run into compiler bugs, because
it's trying to hack it's way around the type system, and if you're not
dealing with class references, there's probably a better way to handle the
problem.
- Jonathan M Davis
How in the name of D do you deal with more than one optional template parameter?
Hi,
Do you guys have any strategies for dealing with templates when
they have more than one optional parameter?
E.g let's say we have a type C that takes three parameters
struct B(T) {}
struct C(string name, T, string desc) {}
And let's say I want T and desc to be optional and T should be of
type B, i.e. I would want to be able to do is this:
auto x = C!("name", B!int)();
auto y = C!("name", B!int, "desc")();
auto z = C!("name", "desc")();
So C is a template that must have a name, and can optionally have
a B, or a description, or both.
The immediate (maybe naive) way that comes to mind is:
struct C(string name, rest...)
if (rest.length <= 2)
if (rest has one elements then it can be either template B or a
string) // how?
if (rest has two elements then it must be template B followed by
string) // how?
{
static if (rest[0] is type B) {
enum hasB = true;
static if (rest.length > 1) {
string desc = rest[1];
}
} else {
enum hasB = false;
if (rest.length) {
string desc = rest[1];
} else {
string desc = null;
}
}
// Now I have access to a desc if it was provided
// And a boolean that tells me if I have a B type.
// But dayum that was a lot of hoops.
}
Giving it some more thought, one could do this too:
struct Void {}
struct C(string name, T, string desc)
if (isInstanceOf!(B, T) || is(T == Void)
{}
template C(string name T) {
alias C = C!(name, T, null);
}
template C(string name, string desc) {
alias C = C!(name, Void, desc);
}
Which requires one to create this meta-Void type to get to work.
Which I guess is not that bad. But, anyway.
Are there other ways? Or does anyone have any tips on how to deal
with this? Or is the alias way generally the way to go?
Cheers,
- Ali
Re: How in the name of D do you deal with more than one optional template parameter?
On Tue, Oct 30, 2018 at 08:46:31PM +, aliak via Digitalmars-d-learn wrote:
> Hi,
>
> Do you guys have any strategies for dealing with templates when they
> have more than one optional parameter?
>
> E.g let's say we have a type C that takes three parameters
>
> struct B(T) {}
> struct C(string name, T, string desc) {}
>
> And let's say I want T and desc to be optional and T should be of type
> B, i.e. I would want to be able to do is this:
>
> auto x = C!("name", B!int)();
> auto y = C!("name", B!int, "desc")();
> auto z = C!("name", "desc")();
>
> So C is a template that must have a name, and can optionally have a B,
> or a description, or both.
>
> The immediate (maybe naive) way that comes to mind is:
>
> struct C(string name, rest...)
> if (rest.length <= 2)
> if (rest has one elements then it can be either template B or a string) //
> how?
> if (rest has two elements then it must be template B followed by string) //
> how?
struct C(Args...)
if ((rest.length == 2 && is(Args[0] == B!C, C) && is(Args[1] ==
string)) ||
(rest.length == 1 && (is(Args[0] == B!C, C) || is(Args[0] ==
string
{
...
}
[...]
> Giving it some more thought, one could do this too:
>
> struct Void {}
This is unnecessary. Why not just use `void` directly?
struct C(string name, T, string desc)
if (is(T : B!C, C) || is(T == void))
{
...
}
> Are there other ways? Or does anyone have any tips on how to deal with
> this? Or is the alias way generally the way to go?
[...]
You can also use default parameters for templates:
struct C(string name, T, string desc = null)
{
...
}
then you just need one more alias for the string-only variant:
alias C(string name, string desc) = C!(name, void, desc);
Note that this syntax is much shorter than the full eponymous template
syntax, which makes it easier to deal with longer parameter lists:
struct ManyParams(A a, B b=defaultB, C c=defaultC, D d=defaultD)
{
...
}
alias ManyParams(A a, C c, D d=defaultD) = ManyParams!(a, null, c, d);
alias ManyParams(A a, D d=defaultD) = ManyParams!(a, void, void, d);
And so on.
And there's probably a way to auto-generate those alias templates if you
anticipate needing to do this many times. (Or if you're insane and want
to let the user specify different arguments in any order.) Mixins and
CTFE codegen FTW! :-D
T
--
A mathematician is a device for turning coffee into theorems. -- P. Erdos
std.math log and family
I've discovered that the 'log' function as well several similar functions are only defined as taking a real argument and returning a real, unlike most other std.math functions, which have triple definitions (also supporting double and float types). This created a problem when I tried compiling code like the following: --- import std.math; alias double function(double) Funcptr; Funcptr sinptr = &sin; Funcptr tanptr = &tan; Funcptr logptr = &log; --- dmd (and ldc2) report test.d(7): Error: cannot implicitly convert expression & log of type real function(real x) pure nothrow @nogc @safe to double function(double) [ldc2 also reports test.d(6): Error: cannot implicitly convert expression & tan of type real function(real x) pure nothrow @nogc @trusted to double function(double) but apparently this is an LDC-only problem] I'd like to know if the lack of double/float versions of 'log', 'log10', etc. are intentional, i.e., there's some rationale behind it, or an oversight. I'd also like to know the proper/best way to deal with the error, considering the real code embeds the 'Funcptr's in an array of structs. Is it better to write a function 'mylog' that internally casts the argument and the return value, or is there some safe way to cast away the 'log' function at the point of initializing the array? Also, is it preferable to post the first question (intentional/oversight) in the Phobos forum? And what is the preferred way of reporting the LDC problem, via GitHub?
Re: std.math log and family
On Wed, Oct 31, 2018 at 12:48:03AM +, Joe via Digitalmars-d-learn wrote:
[...]
> I'd like to know if the lack of double/float versions of 'log',
> 'log10', etc. are intentional, i.e., there's some rationale behind it,
> or an oversight.
It's an oversight. Thanks for bringing it to our attention.
Well, actually there's a historical reason behind it, but that's no
excuse. Please file a bug against Phobos here:
http://issues.dlang.org/
> I'd also like to know the proper/best way to deal with the error,
> considering the real code embeds the 'Funcptr's in an array of
> structs. Is it better to write a function 'mylog' that internally
> casts the argument and the return value, or is there some safe way to
> cast away the 'log' function at the point of initializing the array?
I don't think it's safe to cast the function pointer, because of
mismatching types. You might get undefined behaviour at runtime. Define
your own wrapper instead, as you said, that just forwards the
implementation to std.math.log. You don't need to cast the argument
because it implicitly promotes to real anyway:
float mylog(float arg) { return std.math.log(arg); }
auto funcptr = &mylog;
> Also, is it preferable to post the first question
> (intentional/oversight) in the Phobos forum? And what is the preferred
> way of reporting the LDC problem, via GitHub?
If you're unsure, just ask on the forum. :)
In this case, this is a bug in Phobos itself, so an issue should be
filed at: http://issues.dlang.org/
(While discussion on the forum may be helpful, always remember to file
an issue, because forum discussions may get forgotten after some time,
whereas issues in the bug tracker will eventually get looked at. Don't
be shy to clamor on the forum about bugs that nobody has responded to in
a long time, though. Sometimes things get overlooked and we just need
a reminder.)
T
--
Long, long ago, the ancient Chinese invented a device that lets them see
through walls. It was called the "window".
Re: std.math log and family
On Wednesday, 31 October 2018 at 00:48:03 UTC, Joe wrote: I'd like to know if the lack of double/float versions of 'log', 'log10', etc. are intentional, i.e., there's some rationale behind it, or an oversight. Just laziness or people still thinking that you don't lose any performance by computing in `real` precision. [ldc2 also reports test.d(6): Error: cannot implicitly convert expression & tan of type real function(real x) pure nothrow @nogc @trusted to double function(double) but apparently this is an LDC-only problem] You've got to be using an older LDC version; v1.12 does define tan() for all 3 FP types. I'd also like to know the proper/best way to deal with the error Long-term? Definitely adding the missing implementations to std.math ;), continuing my work here: https://github.com/dlang/phobos/pull/6272 Short-term, I'd go with tiny wrappers.
Re: std.math log and family
On Wed, Oct 31, 2018 at 01:14:37AM +, kinke via Digitalmars-d-learn wrote: > On Wednesday, 31 October 2018 at 00:48:03 UTC, Joe wrote: > > I'd like to know if the lack of double/float versions of 'log', > > 'log10', etc. are intentional, i.e., there's some rationale behind > > it, or an oversight. > > Just laziness or people still thinking that you don't lose any > performance by computing in `real` precision. Is it true that on modern hardware computing with `real` reverts to slow x87 emulation in the CPU instead of using SSE/MMX/whatever native math functions? I've heard that said a lot, I'm just wondering if there's actual measurements to back that up. [...] > > I'd also like to know the proper/best way to deal with the error > > Long-term? Definitely adding the missing implementations to std.math ;), > continuing my work here: https://github.com/dlang/phobos/pull/6272 > Short-term, I'd go with tiny wrappers. Yeah, going forward std.math definitely needs to have native float/double counterparts for all functions. Preferably CTFE-eable versions of them all, so that I can compute my math lookup tables at compile-time. :-D T -- Любишь кататься - люби и саночки возить.
