Re: scope(~this)
On Monday, 13 March 2017 at 14:28:01 UTC, Inquie wrote:
On Monday, 13 March 2017 at 05:18:18 UTC, Nicholas Wilson wrote:
On Sunday, 12 March 2017 at 21:38:44 UTC, Inquie wrote:
Is there any easy way to create a scope for termination of
the object?
I have a template method that takes a type and allocates and
deallocates based on that type.
class bar
{
void foo(T)()
{
T x;
alloc(x);
scope(~this) dealloc(x); // hypothetical that wraps the
statement in a lambda and deallocates in the destructor
... x must stay allocated until class instance
termination(has to do with COM, can't release it in foo)
}
}
I think the feature you're asking for is too complicated/involved
for a language feature. Because it means there must be some
implicit array in each object of your 'bar' class that holds some
number of closures that will be executed in destructor. This
affects object's memory layout and raises questions of allocating
memory for those closures and since those closures will have
pointers to some data (like 'x' here) it affects garbage
collection. So there are a lot of things to be careful about and
things that might affect other language features we haven't
thought about yet. This is something quite big and something that
affects a lot of code, not just a couple of classes you'll write
in your one app. Probably it would be better to implement it as a
library feature. Just make a base class having a method for
registering such closures and calling them in destructor, and
inherit from it or just embed it in your 'bar'.
Re: Phobos function to check if files are identical?
On Monday, 13 March 2017 at 17:47:09 UTC, H. S. Teoh wrote: Binary comparison is easy. Just read the files by fixed-sized chunks and compare them. Follow up question... What is the best @safe way? Since File.byChunk() is @system. Just out of curiosity, I would rather use it and flag my code @trusted, although I guess there could be concurrency issues I have to take into account anyway... anything else?
Re: code folding
On Tuesday, 14 March 2017 at 00:38:12 UTC, Vladimir Panteleev wrote: If you have enough declarations in one file that they call for code folding, it may be better to move them to a separate module. Public imports and aliases allow doing this without breaking any code. [...] Generally speaking, I would recommend to simply avoid code folding altogether: https://blog.codinghorror.com/the-problem-with-code-folding/ Indeed good point: http://stackoverflow.com/questions/475675/when-is-a-function-too-long
Re: Null-Safe Dereference Operator
On Tuesday, 14 March 2017 at 01:08:50 UTC, Jonathan M Davis wrote:
It does not, though if you really wanted to, you could probably
create template that did the same thing fairly easily.
I recently added something similar to dom.d, since I wanted to
pull a header if present, and was ok with a null string if there
wasn't one.
I used to write:
string header;
if(auto e = document.querySelector("h1"))
header = e.innerText;
but now i can write:
string header = document.optionSelector("h1").innerText;
http://dpldocs.info/experimental-docs/arsd.dom.Element.optionSelector.html
Since the selector syntax is already a DSL for descending into
the tree, you don't typically need to chain it far, but the
optionSelector magic allows it anyway:
// all of this becomes null-safe dereferencing...
document.optionSelector("h1").firstChild.nextSibling.innerText
The return value is a new type:
http://dpldocs.info/experimental-docs/arsd.dom.MaybeNullElement.html
That uses opDispatch and type checking to wrap. Here is the
complete source code, that you might be able to adapt to your
object too, or make it REALLY generic and use it anywhere:
---
struct MaybeNullElement(SomeElementType) {
this(SomeElementType ele) {
this.element = ele;
}
SomeElementType element;
/// Forwards to the element, wit a null check inserted that
propagates null.
auto opDispatch(string method, T...)(T args) {
alias type = typeof(__traits(getMember, element, method)(args));
static if(is(type : Element)) {
if(element is null)
return MaybeNullElement!type(null);
return __traits(getMember, element, method)(args);
} else static if(is(type == string)) {
if(element is null)
return cast(string) null;
return __traits(getMember, element, method)(args);
} else static if(is(type == void)) {
if(element is null)
return;
__traits(getMember, element, method)(args);
} else {
static assert(0);
}
}
/// Allows implicit casting to the wrapped element.
alias element this;
}
---
Now, the C# thing is cool because you can use it with any object,
but in my experience, I don't *need* it with most objects. I
found I mostly want it with XML and JSON, so I just adapted those
two specific classes to allow something like the above and now
get a decent amount of mileage out of it without needing the
general-purpose operator.
You can templatize that MaybeNull thing to work on arbitrary
objects too, then write like
`NullSafe(obj).chain.as.much.as.you.want` if you like, but
another benefit of me finding I mostly wanted it on just those
two things is I made a shortcut method: document.optionSelector
rather than `nullSafe(document.querySelector)` or whatever.
You could also make some kind of UFCS null safe chainer:
obj.ns.foo.ns.bar
where there is a NullSafe!T ns(T obj) {} that returns a null-safe
wrapper; a user-defined function taking the place of the language
operator.
So, no, D doesn't have the C# thing, but there are a few other
options you can explore to do something similar.
Re: Declaring interfaces with a constructor
On Monday, 13 March 2017 at 19:31:52 UTC, David Zhang wrote:
Basically, I want to define a common interface for a group of
platform-specific classes, except that they should ideally also
share constructor parameters. What I want to do is then alias
them to a common name, selecting the implementation for the
target platform at compile time.
like this?
--
import std.stdio;
abstract class PublicInterface
{
this(int, int) {} // must have body, see below
}
version(broken) {
alias ActualImpl = NotCompile;
}
else {
alias ActualImpl = PlatformSpecificClass;
}
// put behind version too, this just for demonstration
class PlatformSpecificClass : PublicInterface
{
this(int a, int b)
{
super(a,b); // yeah, downside of this approach
writeln(a,b);
}
}
version(broken) {
class NotCompile : PublicInterface
{
// no interface ctor
}
}
void main()
{
new ActualImpl(1,2);
}
-
there is also way to do this using templates and duck typing, I
think it will be more idiomatic way since ranges and stuff
heavily use it to provide such generalism, though just like you
say, I would prefer to have strict interface for such use case...
Re: Can i using D & LLVM & SDL2 for Android?
On 14/03/2017 6:08 AM, Joakim wrote: On Monday, 13 March 2017 at 09:33:39 UTC, rikki cattermole wrote: On 13/03/2017 7:48 PM, Joakim wrote: [...] Why exactly doesn't the Android port support dlopen, dlsym and dlclose? It is provided by the NDK libc. At least according to this[0]. [0] https://developer.android.com/ndk/guides/stable_apis.html I was more talking about D shared libraries, which I'm assuming DerelictSDL2 qualifies as and would require Phobos built as a shared library. That hasn't been tried yet on Android. DerelictSDL2 would be statically linked, it would dynamically bind via dlopen, dlsym and dlclose to SDL itself which would be compiled as a shared library. This is how Derelict based libraries work.
Re: Null-Safe Dereference Operator
On Tuesday, March 14, 2017 00:51:02 Jolly James via Digitalmars-d-learn wrote: > Does anybody know, if D has a null-safe dereference operator like > C# does (?.) or something similar? It does not, though if you really wanted to, you could probably create template that did the same thing fairly easily. - Jonathan M Davis
Re: code folding
On Monday, 13 March 2017 at 21:33:56 UTC, Inquie wrote: One can say that it is a useless feature because D doesn't have it... or one could say that D is useless because it doesn't have it. A nice balance is simply to say "It is a useful feature that has proven it's worth and it is time that D implements something like it". As D becomes more mainstream, these features will be requested. D should learn from other language/compilers just as other languages/compilers have learned from it. (it's a two a way street) FYI: The "you must implement my feature request or D will never succeed" attitude is rather common and never helpful. Not to mention that such an argument would be demonstrably false: every popular language without the feature you want has apparently succeeded despite not having said feature. When one had a shit load of types in a single file, it is nice to be able to fold them. It is also nice to be able to group them in some way(hence the question) and fold the group so that large chunks of the file can be visibly reduced. If you have enough declarations in one file that they call for code folding, it may be better to move them to a separate module. Public imports and aliases allow doing this without breaking any code. If you would like a way to achieve code folding without involving language constructs, I think the starting point would be your IDE/editor's D plugin vendor. Once implemented in one editor, the syntax could be implemented in others and be informally standardized. I don't think that it would make sense to introduce it into the language syntax proper. The #region syntax in C# makes sense for C# because, as already mentioned, the language vendor is also the main IDE vendor; but also because C#, like Java, requires a lot more boilerplate - writing programs in C# is much more tedious without an IDE than with. This is not the case of D, which was designed to solve problems that would otherwise require boilerplate code in the language itself. Generally speaking, I would recommend to simply avoid code folding altogether: https://blog.codinghorror.com/the-problem-with-code-folding/
Re: code folding
On Monday, March 13, 2017 19:51:59 Inquie via Digitalmars-d-learn wrote:
> On Monday, 13 March 2017 at 18:26:22 UTC, Jonathan M Davis wrote:
> > On Monday, March 13, 2017 17:29:41 Inquie via
> >
> > Digitalmars-d-learn wrote:
> >> Does D have any nice way to specify a block for cold folding?
> >> I have a very large set of structs and I'd like to be able to
> >> code fold them all at once and together.
> >>
> >> I have been using
> >>
> >> static if(true)
> >> {
> >>
> >> ... junk
> >>
> >> }
> >>
> >> but the static if is uninformative since that is the only line
> >> that is shown when folded. A comment helps but still kinda
> >> ugly.
> >>
> >> C# has #regions and hopefully D has something as useful.
> >
> > Code-folding is an IDE thing, not a language thing. So, it's
> > not the sort of thing that would normally be built into a
> > language. If Microsoft did it with C#, it's only because they
> > assumed that everyone would use Visual Studio, but I would
> > guess that #region actually does more than just enable code
> > folding. However, since I've done relatively little with C#, I
> > don't know.
> >
> > So, how code folding works is going to depend entirely on
> > whatever IDE or code editor you're using. If you told us which
> > IDE you were using, maybe someone here could give you some
> > tips, but it's going to be specific to your IDE. Normally, I
> > think that folks just code fold based on braces if they're
> > doing fode folding, but I don't know. I've certainly never
> > heard of anyone adding anything to a source file just to enable
> > code folding.
> >
> > - Jonathan M Davis
>
> This is wrong. It is a language feature.
I mean that the code folding itself is not a language feature. It's
something that the IDE does. The compiler doesn't care one whit about code
folding. If #region in C# is there to tell the IDE that the programmer wants
that to be foldable, and that's all it does, then the language has a feature
to help inform IDEs about how the program wants the code to be foldable.
It's still not the language or compiler that does the code folding.
And as I said, if C# has something like this, it's because Microsoft assumed
that you were going to be using Visual Studio, which they control. Languages
don't normally have any features that have anything to do with code editors,
because they don't normally assume anything about the editor that you're
using. C++ doesn't have anything like it (though it looks like Microsoft
added a non-standard extension for it). Neither does Java, python, ruby,
javascript, or PHP - just to name a few. There may be _some_ other language
out there that does, but it's simply not the sort of thing that most
languages do, because they're not usually written with specific editors in
mind. Microsoft with C# is the oddball here, because they control both the
language and the primary editor.
- Jonathan M Davis
Re: Recursive template instantiation
On 03/13/2017 11:58 PM, Stefan Koch wrote:
On Monday, 13 March 2017 at 22:05:24 UTC, Jack Applegame wrote:
Is this a bug?
No it's not
struct C
{
B!C;
}
is an error.
Howto compute C ? <--\
let's check the members; |
The member needs a template. |
Howto compute the template ? |
let's compute the parameters. |
What is the first Parameter ? |
Its C. |
Howoto compute C---/
I don't think that's it.
Here's a variant where B is not instantiated with C:
struct A()
{
~this() { enum s = C.sizeof; }
}
struct B() { A!() foo; }
struct C { B!() bar; }
How to compute C?
Check members.
For member `B!() bar;`, resolve `B!()`.
Check members of `B!()`.
For member `A!() foo;` resolve `A!()`.
Check members of `A!()`.
No members => size = 0 (or rather 1, I guess).
Bubble up.
But the compiler seems to get confused by the destructor. I guess it
incorrectly(?) sees a need to analyze C again before it can finish up
`A!()`?
Re: Recursive template instantiation
On 03/14/2017 12:02 AM, Stefan Koch wrote:
On Monday, 13 March 2017 at 22:59:36 UTC, ag0aep6g wrote:
[...]
struct A(T) {
void m() {
char[T.sizeof] data;
}
}
/* ... rest as above ... */
I don't see how the destructor makes a difference. Soo, bug?
Try to use m.
Works no problem?
struct A(T) {
void m() {
char[T.sizeof] data;
import std.stdio;
writeln(T.sizeof);
}
}
struct B(T) {
A!T foo;
}
struct C {
B!C bar;
}
void main() {
C c;
c.bar.foo.m();
}
Prints "1".
Re: Recursive template instantiation
On Monday, 13 March 2017 at 22:59:36 UTC, ag0aep6g wrote:
On 03/13/2017 03:26 PM, Jack Applegame wrote:
I'm pretty sure that this code should compile
(https://dpaste.dzfl.pl/cf1e1ee6ef4b):
struct A(T) {
~this() {
char[T.sizeof] data;
}
}
struct B(T) {
A!T foo;
}
struct C {
B!C bar;
}
void main() {
C c;
}
But it doesn't:
/d300/f416.d(3): Error: struct f416.C no size because of
forward
reference /d300/f416.d(12): Error: template instance
f416.B!(C) error
instantiating
It compiles when it's a normal method instead of a destructor:
struct A(T) {
void m() {
char[T.sizeof] data;
}
}
/* ... rest as above ... */
I don't see how the destructor makes a difference. Soo, bug?
Try to use m.
Re: Recursive template instantiation
On 03/13/2017 03:26 PM, Jack Applegame wrote:
I'm pretty sure that this code should compile
(https://dpaste.dzfl.pl/cf1e1ee6ef4b):
struct A(T) {
~this() {
char[T.sizeof] data;
}
}
struct B(T) {
A!T foo;
}
struct C {
B!C bar;
}
void main() {
C c;
}
But it doesn't:
/d300/f416.d(3): Error: struct f416.C no size because of forward
reference /d300/f416.d(12): Error: template instance f416.B!(C) error
instantiating
It compiles when it's a normal method instead of a destructor:
struct A(T) {
void m() {
char[T.sizeof] data;
}
}
/* ... rest as above ... */
I don't see how the destructor makes a difference. Soo, bug?
Re: Recursive template instantiation
Is this a bug?
Re: code folding
On Monday, 13 March 2017 at 19:51:59 UTC, Inquie wrote: This is wrong. It is a language feature. #region lets you specify a block of code that you can expand or collapse when using the outlining feature of the Visual Studio Code Editor. In longer code files, it is convenient to be able to collapse or hide one or more regions so that you can focus on the part of the file that you are currently working on. The following example shows how to define a region: Obviously it is useful for the IDE, but if it was not a language feature then the code would not compile(as it's not a comment). From my understanding of the feature, it does the same as // region ... code to be folded ... // endregion An IDE can then read those comments and allow code folding. It might meet some definition of a language feature, but it is nothing more than a comment. I use visual studio and if it was an IDE feature then I could insert #regions in it and it would compile. This would, of course, break anyone else code that doesn't use an IDE that supports it... hence it has to be a language feature(or some type of meta comment thing, which it is not in this case). I don't understand how it would break your code.
Re: code folding
On Monday, 13 March 2017 at 21:17:31 UTC, XavierAP wrote:
On Monday, 13 March 2017 at 17:29:41 UTC, Inquie wrote:
I have been using
static if(true)
{
... junk
}
Indeed #region is part of the C# specification, even if it has
no effect on the code. (The specification does not say anything
about folding/collapsing, just about "marking sections of
code", although I guess most IDEs supporting it will follow the
example of MS's reference implementation.)
Short answer, D does not have this, as far as I know.
I don't really think it's good substitute practice to insert
meaningless static if(true)... Even if you're really used to
that feature, and even if you're right that it does the job and
doesn't change the generated code.
Unfortunately you can't get this folding easily (I'm sure some
Vim wizard would come up with something). Instead if you want
to mark regions of code, that's what comments are for. You
can't get the folding you want unfortunately (outside of
naturally existing bracket pairs) but you can use your editor
to search forward and backward in the file for whatever text,
e.g.
//region: foo//
That's not the point. The point is that the IDE I use(VS, which
is the most common IDE on windows), requires an actual block to
fold. Folding is useful so it is not an irrelevant issue. Even
notepad++ can fold blocks if it can determine what a block, so
this isn't an "IDE" specific thing nor an "IDE" specific feature.
When one had a shit load of types in a single file, it is nice to
be able to fold them. It is also nice to be able to group them in
some way(hence the question) and fold the group so that large
chunks of the file can be visibly reduced.
One can say that it is a useless feature because D doesn't have
it... or one could say that D is useless because it doesn't have
it. A nice balance is simply to say "It is a useful feature that
has proven it's worth and it is time that D implements something
like it". As D becomes more mainstream, these features will be
requested. D should learn from other language/compilers just as
other languages/compilers have learned from it. (it's a two a way
street)
If D supported such simple stuff hacks would not be required to
do the simple things.
Re: Phobos function to check if files are identical?
On Monday, 13 March 2017 at 17:47:09 UTC, H. S. Teoh wrote: Why it is not easy to do by hand? Sorry typo, I had intended to type "I know it is easy"
Re: code folding
On Monday, 13 March 2017 at 17:29:41 UTC, Inquie wrote:
I have been using
static if(true)
{
... junk
}
Indeed #region is part of the C# specification, even if it has no
effect on the code. (The specification does not say anything
about folding/collapsing, just about "marking sections of code",
although I guess most IDEs supporting it will follow the example
of MS's reference implementation.)
Short answer, D does not have this, as far as I know.
I don't really think it's good substitute practice to insert
meaningless static if(true)... Even if you're really used to that
feature, and even if you're right that it does the job and
doesn't change the generated code.
Unfortunately you can't get this folding easily (I'm sure some
Vim wizard would come up with something). Instead if you want to
mark regions of code, that's what comments are for. You can't get
the folding you want unfortunately (outside of naturally existing
bracket pairs) but you can use your editor to search forward and
backward in the file for whatever text, e.g.
//region: foo//
Re: code folding
On Monday, 13 March 2017 at 18:26:22 UTC, Jonathan M Davis wrote:
On Monday, March 13, 2017 17:29:41 Inquie via
Digitalmars-d-learn wrote:
Does D have any nice way to specify a block for cold folding?
I have a very large set of structs and I'd like to be able to
code fold them all at once and together.
I have been using
static if(true)
{
... junk
}
but the static if is uninformative since that is the only line
that is shown when folded. A comment helps but still kinda
ugly.
C# has #regions and hopefully D has something as useful.
Code-folding is an IDE thing, not a language thing. So, it's
not the sort of thing that would normally be built into a
language. If Microsoft did it with C#, it's only because they
assumed that everyone would use Visual Studio, but I would
guess that #region actually does more than just enable code
folding. However, since I've done relatively little with C#, I
don't know.
So, how code folding works is going to depend entirely on
whatever IDE or code editor you're using. If you told us which
IDE you were using, maybe someone here could give you some
tips, but it's going to be specific to your IDE. Normally, I
think that folks just code fold based on braces if they're
doing fode folding, but I don't know. I've certainly never
heard of anyone adding anything to a source file just to enable
code folding.
- Jonathan M Davis
This is wrong. It is a language feature.
#region lets you specify a block of code that you can expand or
collapse when using the outlining feature of the Visual Studio
Code Editor. In longer code files, it is convenient to be able to
collapse or hide one or more regions so that you can focus on the
part of the file that you are currently working on. The following
example shows how to define a region:
Obviously it is useful for the IDE, but if it was not a language
feature then the code would not compile(as it's not a comment).
I use visual studio and if it was an IDE feature then I could
insert #regions in it and it would compile. This would, of
course, break anyone else code that doesn't use an IDE that
supports it... hence it has to be a language feature(or some type
of meta comment thing, which it is not in this case).
Just because you have never heard of it doesn't mean much... it
is anecdotal... before the year 0BC no one ever heard of
computers... or antibiotics, or spacecraft, or transistors, or
just about anything we have to day.
Re: Phobos function to check if files are identical?
On Mon, Mar 13, 2017 at 10:47:09AM -0700, H. S. Teoh via Digitalmars-d-learn
wrote:
[...]
> P.S. I just realized that std.stdio.chunks() doesn't return a range.
> Bah. File an enhancement request. I might even submit a PR for it. ;-)
[...]
> P.P.S. It's not overly hard to write an alternative version of
> std.stdio.chunks that returns a real range.
[...]
Bah, I'm an idiot. Just use File.byChunk instead of .chunks. Here's a
fully-working example:
import std.stdio;
bool equal(File f1, File f2)
{
import std.algorithm.comparison : equal;
enum bufSize = 4096;
return f1.byChunk(bufSize).equal(f2.byChunk(bufSize));
}
int main(string[] args) {
if (args.length < 3)
{
stderr.writeln("Please specify filenames");
return 1;
}
if (equal(File(args[1]), File(args[2])))
writeln("Files are identical.");
else
writeln("Files differ.");
return 0;
}
T
--
INTEL = Only half of "intelligence".
Re: Declaring interfaces with a constructor
On Monday, 13 March 2017 at 17:52:09 UTC, XavierAP wrote: On Monday, 13 March 2017 at 02:15:21 UTC, David Zhang wrote: What it says on the tin. Is there a way to create interfaces with a constructor or must I use an abstract class. What do you want to do in your constructor? I can't think of anything that wouldn't change some state, either of the class (but interfaces aren't allowed to have fields either, precisely because they may not have state), or the global state (worse...). Just curious. Additionally, is there a way to force the linker to link a function in a class without an implementation with another that does have an implementation? I'm not sure if you mean the same as generating "interface files"? [1] https://dlang.org/dmd-windows.html#interface-files Basically, I want to define a common interface for a group of platform-specific classes, except that they should ideally also share constructor parameters. What I want to do is then alias them to a common name, selecting the implementation for the target platform at compile time.
Re: TLS
On 13.03.2017 14:35, M-exe wrote: On Friday, 10 March 2017 at 21:32:05 UTC, sarn wrote: On Friday, 10 March 2017 at 19:24:29 UTC, bauss wrote: Mark your variables with __gshared. I would say shred, but it has some restrictions to it, where __gshared is the equivalent to global variables in C. immutable variables are also not put in TLS. Thank you for yours replys but there is a tls directory even when I compile empty main.. It's very likely that there are TLS variables in druntime that are linked in. You can identify them by looking at the map file.
Re: code folding
On Monday, March 13, 2017 17:29:41 Inquie via Digitalmars-d-learn wrote:
> Does D have any nice way to specify a block for cold folding? I
> have a very large set of structs and I'd like to be able to code
> fold them all at once and together.
>
> I have been using
>
> static if(true)
> {
> ... junk
> }
>
> but the static if is uninformative since that is the only line
> that is shown when folded. A comment helps but still kinda ugly.
>
> C# has #regions and hopefully D has something as useful.
Code-folding is an IDE thing, not a language thing. So, it's not the sort of
thing that would normally be built into a language. If Microsoft did it with
C#, it's only because they assumed that everyone would use Visual Studio,
but I would guess that #region actually does more than just enable code
folding. However, since I've done relatively little with C#, I don't know.
So, how code folding works is going to depend entirely on whatever IDE or
code editor you're using. If you told us which IDE you were using, maybe
someone here could give you some tips, but it's going to be specific to your
IDE. Normally, I think that folks just code fold based on braces if they're
doing fode folding, but I don't know. I've certainly never heard of anyone
adding anything to a source file just to enable code folding.
- Jonathan M Davis
Re: Phobos function to check if files are identical?
P.P.S. It's not overly hard to write an alternative version of
std.stdio.chunks that returns a real range. Something like this should
do:
// Warning: untested code
auto realChunks(File f, size_t blockSize)
{
static struct Result
{
private File f;
private ubyte[] buffer;
bool empty = true;
ubyte[] front;
this(File _f, size_t blockSize)
{
f = _f;
buffer.length = blockSize;
empty = false;
popFront();
}
void popFront()
{
front = f.rawRead(buffer);
if (front.length == 0)
empty = true;
}
}
return Result(f, blockSize);
}
T
--
A program should be written to model the concepts of the task it performs
rather than the physical world or a process because this maximizes the
potential for it to be applied to tasks that are conceptually similar and, more
important, to tasks that have not yet been conceived. -- Michael B. Allen
Re: Phobos function to check if files are identical?
On Mon, Mar 13, 2017 at 04:50:49PM +, XavierAP via Digitalmars-d-learn
wrote:
> It's not easy to do by hand of course, but I was wondering if there
> was one simple function taking two file names and just returning a
> bool or something like that. I haven't found it in std.file.
Why it is not easy to do by hand? All you have to do is open the two
files, then iterate over their data and compare. Of course, you'd want
to chunk them up to minimize I/O roundtrips, but it'd be something along
the lines of:
bool isEqual(string filename1, string filename2) {
import std.algorithm.comparison : equal;
import std.range : zip;
import std.stdio : File, chunks;
auto f1 = File(filename1);
auto f2 = File(filename2);
size_t blockSize = 4096; // or something similar
return f1.chunks(blockSize).equal(f2.chunks(blockSize));
}
> If such a function doesn't exist in Phobos but there's a good
> implementation in some other library, I'm interested to know. Although
> this time it's for a unit test so I'd rather implement it in two lines
> than add a dependency.
>
> And otherwise to write it by hand, how do you think is the best way?
> And in terms of performance? By chunks in case of a binary comparison?
> And what about the case of a text comparison?
[...]
Binary comparison is easy. Just read the files by fixed-sized chunks and
compare them.
Text comparison is a can of worms. What kind of comparison do you have
in mind? Case-sensitive or insensitive? Is it ASCII or Unicode? What
kind of Unicode encoding is involved? Are the files expected to be in
one of the normalization forms, or is it free-for-all? Do you expect
grapheme equivalence or just character equivalence? Depending on the
answer to these questions, text comparison can range from trivial to
hair-raisingly complex.
But the fundamental ideas remain the same: read a stream of characters /
graphemes from each file in tandem, preferably buffered, and compare
them using some given comparison function.
P.S. I just realized that std.stdio.chunks() doesn't return a range.
Bah. File an enhancement request. I might even submit a PR for it. ;-)
T
--
There are four kinds of lies: lies, damn lies, and statistics.
Re: Declaring interfaces with a constructor
On Monday, 13 March 2017 at 02:15:21 UTC, David Zhang wrote: What it says on the tin. Is there a way to create interfaces with a constructor or must I use an abstract class. What do you want to do in your constructor? I can't think of anything that wouldn't change some state, either of the class (but interfaces aren't allowed to have fields either, precisely because they may not have state), or the global state (worse...). Just curious. Additionally, is there a way to force the linker to link a function in a class without an implementation with another that does have an implementation? I'm not sure if you mean the same as generating "interface files"? [1] https://dlang.org/dmd-windows.html#interface-files
code folding
Does D have any nice way to specify a block for cold folding? I
have a very large set of structs and I'd like to be able to code
fold them all at once and together.
I have been using
static if(true)
{
... junk
}
but the static if is uninformative since that is the only line
that is shown when folded. A comment helps but still kinda ugly.
C# has #regions and hopefully D has something as useful.
Re: Can you fix this code to avoid using pointers?
On Monday, 13 March 2017 at 14:47:20 UTC, H. S. Teoh wrote:
On Sat, Mar 11, 2017 at 08:07:39PM +, XavierAP via
Digitalmars-d-learn wrote: [...]
But I still like the version with pointers ;)
There's nothing wrong with using pointers in D. The fact that
D alleviates most cases of (explicit) pointers is a testament
to just how awesome it is. ;-) But that shouldn't deter anyone
from using (explicit) pointers once in a while. In fact, D
makes it such that it's a lot safer using pointers than in
C/C++, mainly because it alleviates most of the dangerous use
cases for pointers so what's left is generally harmless stuff.
Unless your code for whatever reason is involved in heavy
pointer hackery (like OS writing), but that's not a typical use
case.
I did it again ;)
enum params = [
"Radius of disk in m",
"Integration step size along radius",
"Total integration time in s",
"Integration step size along time",
"Time step size for output",
"Initial temperature in C",
"Edge temperature in C",
"Flow temperature in C",
"2D conductivity in W K^-1",
"2D diffusivity in m^2 s^-1",
"Convective coefficient in W m^-2 K^-1" ];
real*[params.length] vals = [
, , , , ,
, , ,
, , ];
import std.conv: to;
/* ... */
foreach(i, param; params)
{
/* ... */
*vals[i] = to!real(val);
}
I had the same requirement to make separate named scalars instead
of an array; but also an array was handier to assign the values
inside a loop; and I needed a readable and simple way to map
between them. An array of pointers is perfect I think.
And the only dangerous thing I could do with the pointers is
arithmetic on them instead of the pointed values, but: "pointer
arithmetic not allowed in @safe functions." So all is good :)
Re: TLS
On Friday, 10 March 2017 at 06:41:46 UTC, M-exe wrote: I found that D is great language, but for my own reasons I'm trying to use it without TLS at all. Can the TLS directory be avoided? (compiling on windows) I don't know what you mean by the TLS directory, can you explain? I mean, can it avoided without losing GC and main language features? You could probably modify druntime so that it doesn't use any Thread-Local Storage, but Phobos uses it extensively, as global and static variables are put in TLS by default since D 2.030: https://dlang.org/migrate-to-shared.html Are you against emulated TLS also? If not, I have modified dmd, ldc, and druntime to use the same emulated TLS scheme Walter came up with for OS X, for my Android port: https://github.com/dlang/dmd/pull/3643 https://github.com/ldc-developers/ldc/pull/1447 https://github.com/dlang/druntime/pull/784 You may be able to use something similar on Windows, depending on how feasible such an emulated TLS scheme is there and if you want to dig into these details.
Re: Can i using D & LLVM & SDL2 for Android?
On Monday, 13 March 2017 at 09:33:39 UTC, rikki cattermole wrote: On 13/03/2017 7:48 PM, Joakim wrote: [...] Why exactly doesn't the Android port support dlopen, dlsym and dlclose? It is provided by the NDK libc. At least according to this[0]. [0] https://developer.android.com/ndk/guides/stable_apis.html I was more talking about D shared libraries, which I'm assuming DerelictSDL2 qualifies as and would require Phobos built as a shared library. That hasn't been tried yet on Android. On Monday, 13 March 2017 at 10:11:35 UTC, Mike Parker wrote: On Monday, 13 March 2017 at 06:48:01 UTC, Joakim wrote: [...] The alpha release of DerelictSDL2 3.0 supports static linking. When compiling manually, it requires -version=DerelictSDL_static on the command line and all files matching "derelict/sdl2/internal/*_dyn*.d" should be excluded from the build. When building DerelictSDL2 with DUB, specifying -cderelict-sdl2-static gets the job done, or the same can be added as a subConfiguration value in a project's dub.json/sdl file. Thanks for the update, didn't know that.
Phobos function to check if files are identical?
It's not easy to do by hand of course, but I was wondering if there was one simple function taking two file names and just returning a bool or something like that. I haven't found it in std.file. If such a function doesn't exist in Phobos but there's a good implementation in some other library, I'm interested to know. Although this time it's for a unit test so I'd rather implement it in two lines than add a dependency. And otherwise to write it by hand, how do you think is the best way? And in terms of performance? By chunks in case of a binary comparison? And what about the case of a text comparison? Thanks
Re: Can you fix this code to avoid using pointers?
On Sat, Mar 11, 2017 at 08:07:39PM +, XavierAP via Digitalmars-d-learn wrote: [...] > I realized that the code that sparked the question made no sense and > should be done in a different way... As is always the case when these > questions come up. > But I still like the version with pointers ;) There's nothing wrong with using pointers in D. The fact that D alleviates most cases of (explicit) pointers is a testament to just how awesome it is. ;-) But that shouldn't deter anyone from using (explicit) pointers once in a while. In fact, D makes it such that it's a lot safer using pointers than in C/C++, mainly because it alleviates most of the dangerous use cases for pointers so what's left is generally harmless stuff. Unless your code for whatever reason is involved in heavy pointer hackery (like OS writing), but that's not a typical use case. T -- All problems are easy in retrospect.
Re: how to assign tuple named Tuple easily
On Monday, 13 March 2017 at 00:23:36 UTC, ag0aep6g wrote: On 03/13/2017 01:02 AM, Inquie wrote: Ok, it doesn't work for appending though ;) [...] Tuple!(int, "A", double, "B")[] y; y ~= tuple(3, 2.5); Interestingly, this works: Tuple!(int, "A", double, "B")[] y; y.length += 1; y[$ - 1] = tuple(3, 2.5); yeah, seems more like a bug/feature issue. If the compiler can figure it out with assignment, it should also be able to figure it out with appending EXACTLY because what you wrote. Since a default append is effectively the code you wrote above there should be no difference between the two. In fact, I would have hoped that appending built in arrays would have been expanded using the pattern you specifically implemented which should then not produce the error and simplify life.
Re: scope(~this)
On Monday, 13 March 2017 at 05:18:18 UTC, Nicholas Wilson wrote:
On Sunday, 12 March 2017 at 21:38:44 UTC, Inquie wrote:
Is there any easy way to create a scope for termination of the
object?
I have a template method that takes a type and allocates and
deallocates based on that type.
class bar
{
void foo(T)()
{
T x;
alloc(x);
scope(~this) dealloc(x); // hypothetical that wraps the
statement in a lambda and deallocates in the destructor
... x must stay allocated until class instance
termination(has to do with COM, can't release it in foo)
}
}
Now, x cannot be a field because T is unknown(i suppose I
could use object, void*, etc, but...).
If it is COM then you should use IUnknown (the COM root
interface),or if you are expecting multiple calls to foo, an
array of IUnknown. I think the GC will clean up completely for
you in either case and call release(?) on the member(s).
Also as it is COM you probably don't need to template it, just
choose T to be the most recent ancestor of all (old) T's you
would be expecting foo to be instantiated with (e.g. IUnknown
if you expect any COM object.
Sorry, but that is missing the point! First, it isn't that
simple. I do not think the GC will call release as the GC has no
idea of COM nor the interfaces. While it might be safe not to
release them and let the OS deal with it, this is not standard.
The template is to not part of COM but required to dynamically
instantiate the COM interface that is not supplied(using
GetIDsOfNames).
So, the way it work is, I have a function that takes an interface
which specifies the dynamic COM functions. Using
GetIDsOfNames(since that seems to be the only way) gets the
function pointers to these functions in which I build up a new
object representing that interface. The problem is, One must use
CoCreateInterface to create the COM object to use
GetIDsOfNames(neither of which depends on the interface). But
CoCreateInterface returns the interface with the Release function
as a member and this function must be called later(at terminate
of the overall class handling all this stuff).
But since I have to create a variable with the interface to get
the methods and to pass to CoCreateInstance, and eventually use
it to call Release, I can't discard the variable at the end of
the function.
Basically the interface's lifetime must exist for the entirety of
the containing object. Normally one would use the constructor and
class fields to manage this, but it is impossible here because
the actual interfaces are unknown at compile time(they are
extracted from an idl by this class).
The only thing I could do is keep an array of all these IUnknown
interfaces(sorta using the above technique), since IUnknown has
the Release function in it, basically using your suggestion or
what I originally said is a feasible solution.
But this pollutes the class name space unnecessarily(I know it is
just an array, but ultimately should be unnecessary).
Rather, if I could simply use a
scope(~this) or some other mechanism, everything will be
automatically taken care of.
scope(~this) X.Release();
would realize that X, the local variable in the function, will be
used and the GC will not free it just like delegates do(although
it would need to be copied to the heap so future function calls
won't corrupt the value when used on the stack, or, alternatively
I could malloc it in the function instead).
Then, on destruction, the scope is executed. X still exists.
In this case, it's 1 line of code rather than about 5(a class
field array, an append, and calling release on all appends in the
destructor). It's very clear and very precise.
It's very similar to scope(exit) for function but for
classes(since classes can "exit" too).
It may be better to call it
scope(this)
which is more clear(when the scope of the object instance is
over, then "execute" what follows).
I think this feature would actually be quite useful. Instead of
handling many things in the destructor, we can handle them on
site. e.g., any class resources that are allocated could then
have a scope(this) right after allocation to deallocate them
instead of having to push it in the the destructor which
separates the code visually and programmatically. The same
argument which is used to make scope(exit) useful, but on a
higher level... Which, if we follow it, we should then also have
scope(application) or something for application level scope.
Recursive template instantiation
I'm pretty sure that this code should compile
(https://dpaste.dzfl.pl/cf1e1ee6ef4b):
struct A(T) {
~this() {
char[T.sizeof] data;
}
}
struct B(T) {
A!T foo;
}
struct C {
B!C bar;
}
void main() {
C c;
}
But it doesn't:
/d300/f416.d(3): Error: struct f416.C no size because of forward
reference /d300/f416.d(12): Error: template instance f416.B!(C)
error instantiating
Notice that the same C++ code compiles without problems:
template struct A {
~A() {
char data[sizeof(T)];
}
};
template struct B {
A foo;
};
struct C {
B bar;
};
int main() {
C c;
}
A simple recursion is compiled successfully
(https://dpaste.dzfl.pl/5a8ff73bfa88):
struct A(T) {
~this() {
char[T.sizeof] data;
}
}
struct C {
A!C bar;
}
void main() {
C c;
}
Re: how to assign tuple named Tuple easily
On Monday, 13 March 2017 at 14:09:58 UTC, Inquie wrote: Yeah, so, surely though we can extract the names from the variable and then supply those like I mentioned? Yeah, we prolly could, but a simpler thing might be to just use typeof: Tuple!(int, "A")[] x; x ~= typeof(x[0])(3); x ~= tuple!x(3) ? Seems like it would probably be rather trivial with a bit of template code? Yeah, tuple could certainly adapt to do that too, but I see you would write: x ~= tuple!typeof(x)(3, 5.0); and the `tuple!` there is unnecessary: if you already use `typeof(x[0])` (you still need a `[0]` in there to get the type of the element instead of the array), then you can just construct it right there with the next set of parens.
Re: how to assign tuple named Tuple easily
On Monday, 13 March 2017 at 00:51:27 UTC, Adam D. Ruppe wrote:
On Monday, 13 March 2017 at 00:02:12 UTC, Inquie wrote:
I just figured it didn't work in general, but seems to be an
issue with appending.
Oh, it is because of the implicit construction thing, see my
answer here to learn more:
http://stackoverflow.com/a/42285015/1457000
You can construct the named tuple from a tuple() but you can't
convert one to another since the names change the type.
I don't think the language has a solution with this since you
can't implicit construct nor overload operators on built in
arrays (if it is a custom array, you can do an opOpAssign).
What you could do is
alias ShortName = Tuple!(int, "A");
ShortName[] a;
a ~= ShortName(3);
... of course, at that point, you can also just use a regular
struct too...
Yeah, so, surely though we can extract the names from the
variable and then supply those like I mentioned?
Tuple!(int, "A")[] x;
x ~= tuple!(ExtractTupleNames!x)(3);
which would be equivalent to
x ~= tuple!("A")(3)
which, of course, works.
ExtractTupleNames is a template that surely can get the names
from x? Knowing it's type and that every other element of the
type is a "name" it should be able to get the names then provide
them to tuple? From there, we could redefine tuple to do this
automatically as
x ~= tuple!x(3)
? Seems like it would probably be rather trivial with a bit of
template code?
Ok, I did this real quick, maybe you can see how to improve it
and reduce verbosity:
import std.typecons, std.typetuple, std.meta, std.string,
std.array, std.range;
template ExtractTupleNames(T)
{
string fix()
{
enum q = (T.stringof[7..$-3]);
return "alias ExtractTupleNames = AliasSeq!("~q~");";
}
mixin(fix());
}
void main(string[] argv)
{
Tuple!(int, "A", double, "B")[] x;
x ~= tuple!("A", "B")(3, 5.0);
x ~= tuple!(int, "A", double, "B")(3, 5.0);
x ~= tuple!(ExtractTupleNames!(typeof(x)))(3, 5.0);
}
The goal would be to not have to specify the long string each
time.
e.g., the third line would be either
x ~= tuple!(x)(3, 5.0);
or
x ~= tuple!typeof(x)(3, 5.0);
It would be nice if we could pass a "run time" variable since we
are only going to use it's type in the first place(avoids having
to specify the typeof at the call point).
I realize that we will probably have to redefine tuple but I'm ok
with that as it only makes it more robust.
Re: TLS
On Friday, 10 March 2017 at 21:32:05 UTC, sarn wrote: On Friday, 10 March 2017 at 19:24:29 UTC, bauss wrote: Mark your variables with __gshared. I would say shred, but it has some restrictions to it, where __gshared is the equivalent to global variables in C. immutable variables are also not put in TLS. Thank you for yours replys but there is a tls directory even when I compile empty main..
Re: GDC options
On Sun, 2017-03-12 at 16:38 +0100, Johannes Pfau via Digitalmars-d- learn wrote: > […] > > https://github.com/D-Programming-GDC/GDMD/tree/dport > > gdmd -unittest --main > > The unittest flag for GDC is -funittest but there's no flag to > generate > a main function. gdmd generates a temporary file with a main function > to implement this. gdmd is not packaged with gdc so isn't a general solution. gdmd, like rdmd, should be packaged. Having dmd, ldc, and gdc have different command lines is really ### awkward when using SCons and Meson. It is a shame that dmd and ldc do not just use the standard GCC option set. -- Russel. = Dr Russel Winder t: +44 20 7585 2200 voip: sip:russel.win...@ekiga.net 41 Buckmaster Roadm: +44 7770 465 077 xmpp: rus...@winder.org.uk London SW11 1EN, UK w: www.russel.org.uk skype: russel_winder signature.asc Description: This is a digitally signed message part
Re: Can i using D & LLVM & SDL2 for Android?
On Monday, 13 March 2017 at 10:11:35 UTC, Mike Parker wrote: On Monday, 13 March 2017 at 06:48:01 UTC, Joakim wrote: [...] The alpha release of DerelictSDL2 3.0 supports static linking. When compiling manually, it requires -version=DerelictSDL_static on the command line and all files matching "derelict/sdl2/internal/*_dyn*.d" should be excluded from the build. When building DerelictSDL2 with DUB, specifying -cderelict-sdl2-static gets the job done, or the same can be added as a subConfiguration value in a project's dub.json/sdl file. thanks for advices!! :-)
Re: Can i using D & LLVM & SDL2 for Android?
On Monday, 13 March 2017 at 06:48:01 UTC, Joakim wrote: On Thursday, 9 March 2017 at 10:35:18 UTC, dummy wrote: [...] Regarding the link to that forum post, that bug has since been found and fixed. If you're planning on using Derelict, there is an issue where all Derelict libraries are loaded as shared libraries, whereas the Android port currently doesn't support loading shared libraries. If DLangUI is using SDL2, maybe he has a header file that allows him to statically link against SDL2, which you could reuse. Otherwise, you may need to generate one using DStep: https://github.com/jacob-carlborg/dstep or modify the DerelictSDL2 files to allow you to link statically. thx! i will try it. :-D
How can I get changed members in class object?
In hibernate,update object is set all table columns to sql.
code for example:
```
//orm entity
class User {
int id;
string firstName;
string lastName;
}
Session sess = factory.openSession();
User user =sess.createQuery("FROM User WHERE
first_name=:firstName").setParameter("firstName","balabala").uniqueResult!User();
user.lastName = "new balabala";//change last name
sess.update(user);
```
when exec update method ,hibernate generate sql like that
```
UPDATE user SET first_name =?, last_name =? WHERE id=?
```
but i just want to modify or update last_name column, maybe sql is
```
UPDATE user SET last_name =? WHERE id=?
```
does hibernate has a method to update changed columns only？
how can i do that?
Re: Can i using D & LLVM & SDL2 for Android?
On Monday, 13 March 2017 at 06:48:01 UTC, Joakim wrote: If you're planning on using Derelict, there is an issue where all Derelict libraries are loaded as shared libraries, whereas the Android port currently doesn't support loading shared libraries. If DLangUI is using SDL2, maybe he has a header file that allows him to statically link against SDL2, which you could reuse. Otherwise, you may need to generate one using DStep: https://github.com/jacob-carlborg/dstep or modify the DerelictSDL2 files to allow you to link statically. The alpha release of DerelictSDL2 3.0 supports static linking. When compiling manually, it requires -version=DerelictSDL_static on the command line and all files matching "derelict/sdl2/internal/*_dyn*.d" should be excluded from the build. When building DerelictSDL2 with DUB, specifying -cderelict-sdl2-static gets the job done, or the same can be added as a subConfiguration value in a project's dub.json/sdl file.
Re: Can i using D & LLVM & SDL2 for Android?
On 13/03/2017 7:48 PM, Joakim wrote: On Thursday, 9 March 2017 at 10:35:18 UTC, dummy wrote: On Wednesday, 8 March 2017 at 10:24:24 UTC, Joakim wrote: On Tuesday, 7 March 2017 at 12:06:48 UTC, dummy wrote: Just thought. I do want to know. :-) As far as I know is, * LDC2 woring on NDK(yah!) * Native OpenGLES: http://wiki.dlang.org/Build_LDC_for_Android#Build_a_sample_OpenGL_Android_app_ported_to_D * Dlangui working on Android that based on SDL2: https://github.com/buggins/dlangui / https://dlang.org/blog/2016/10/07/project-highlight-dlangui/ regards, Yes, though I have not tried SDL2 myself. https://forum.dlang.org/post/hbumubsbrzffvgria...@forum.dlang.org Ah, you're right. I will trying DerelictSDL2. Thx :-) Regarding the link to that forum post, that bug has since been found and fixed. If you're planning on using Derelict, there is an issue where all Derelict libraries are loaded as shared libraries, whereas the Android port currently doesn't support loading shared libraries. If DLangUI is using SDL2, maybe he has a header file that allows him to statically link against SDL2, which you could reuse. Otherwise, you may need to generate one using DStep: https://github.com/jacob-carlborg/dstep or modify the DerelictSDL2 files to allow you to link statically. Why exactly doesn't the Android port support dlopen, dlsym and dlclose? It is provided by the NDK libc. At least according to this[0]. [0] https://developer.android.com/ndk/guides/stable_apis.html
Re: Can i using D & LLVM & SDL2 for Android?
On Thursday, 9 March 2017 at 10:35:18 UTC, dummy wrote: On Wednesday, 8 March 2017 at 10:24:24 UTC, Joakim wrote: On Tuesday, 7 March 2017 at 12:06:48 UTC, dummy wrote: Just thought. I do want to know. :-) As far as I know is, * LDC2 woring on NDK(yah!) * Native OpenGLES: http://wiki.dlang.org/Build_LDC_for_Android#Build_a_sample_OpenGL_Android_app_ported_to_D * Dlangui working on Android that based on SDL2: https://github.com/buggins/dlangui / https://dlang.org/blog/2016/10/07/project-highlight-dlangui/ regards, Yes, though I have not tried SDL2 myself. https://forum.dlang.org/post/hbumubsbrzffvgria...@forum.dlang.org Ah, you're right. I will trying DerelictSDL2. Thx :-) Regarding the link to that forum post, that bug has since been found and fixed. If you're planning on using Derelict, there is an issue where all Derelict libraries are loaded as shared libraries, whereas the Android port currently doesn't support loading shared libraries. If DLangUI is using SDL2, maybe he has a header file that allows him to statically link against SDL2, which you could reuse. Otherwise, you may need to generate one using DStep: https://github.com/jacob-carlborg/dstep or modify the DerelictSDL2 files to allow you to link statically.
