Re: Where I download Digital Mars C Preprocessor sppn.exe?
On Sunday, 3 April 2022 at 08:37:45 UTC, user1234 wrote: On Saturday, 2 April 2022 at 21:57:02 UTC, Marcone wrote: Where I download Digital Mars C Preprocessor sppn.exe? I need it to use ImportC it's part of the [DMC] toolchain. [DMC]: http://ftp.digitalmars.com/Digital_Mars_C++/Patch/dm857c.zip Guys I think Ali is right... The post was meant as an April fool's joke... It was pretty badly mistimed though, at the time of his posting, it was 3rd April in my place, and undoubtedly 2nd everywhere else
Re: Const Variables
On Sun, Apr 03, 2022 at 03:42:15PM -0700, Ali Çehreli via Digitalmars-d-learn wrote: [...] > In any case, there is no logical constness in D. (However, one can > play tricks like using casts. (Which may be undefined behavior, etc. > etc.)) [...] A thought occurred to me. What is logical const, and how can we make it useful? Useful meaning, it's not just a convention (like in C++) with no hard guarantees and no verifiability. Currently, D has physical const, so `const` cannot be used for things like caching, lazily-initialized objects, and other things that are logically const but not physically const because mutation is involved. But what really is physical const? It's essentially a contract, guaranteed by the language and statically verified by the compiler, that the physical data has not changed. IOW, it's a contract stating that the data physically stored before operation X is identical to the data physically stored after operation X, and that it has not changed in the meantime. Now can we extend this concept to logical const? Perhaps in this way: instead of guaranteeing the physical data is unchanged, what about a contract that guarantees that *externally-observable behaviour* of the object is unchanged? Meaning, the object may actually have changed internally, but as long as this cannot be observed externally (and this includes *future* behaviour of the object -- so we're not just slipping internal state changes under the carpet that may later alter the object's behaviour), to the outside world it behaves as though it were actually const. In the case of lazy initialization, for example, it ought to be provable that the value of the object, as observed by the outside world, cannot change. The initial state where the value is uninitialized is not observed by the outside world; the only observable value only appears after initialization, and does not change henceforth. Similarly for a cached value: it ought to be provable that the first computation of value is the *only* value that can be externally observed; after the initial computation, the value will never change again. In some sense, this is like an extension of ctors initializing immutable values. The compiler tracks whether the variable has been initialized yet, and inside the ctor you can assign to immutable because the uninitialized value is not observable from outside before that. Once assigned, the compiler enforces no subsequent changes. It's also like D's extension of purity, where impure operations are allowed as long as the outside world cannot tell the difference. There should be some way of implementing logical const along these lines that still provides guarantees whilst relaxing the physical immutability rule. T -- It only takes one twig to burn down a forest.
Re: Const Variables
On 4/3/22 11:24, Salih Dincer wrote:
> On Sunday, 3 April 2022 at 14:29:22 UTC, Paul Backus wrote:
>> On Sunday, 3 April 2022 at 13:50:28 UTC, Salih Dincer wrote:
>>> Hi all,
>>>
>>> Do you have a good example of how const variables actually work?
You are right that const is not absolutely necessary. However, it is
such a useful concept that some programming languages don't allow
mutation at all.
Immutability is seen to be so valuable that some people argue that the
default in D should be immutable. (Rust is just one example where the
default is const. In that language, you have to use 'mut' (presumably
short for "mutable") for variables that can be mutated.)
>> This is covered in the const FAQ:
>>
>> https://dlang.org/articles/const-faq.html
>
> The programs I write are not multithreaded. Also, I don't work as a
> team.
So you agree with that article. :) The rest of us who work with
multi-threaded programs or with other developers agree with it as well. ;)
> Thanks for the link but there is only the following example:
>
> ```d
> struct Foo
> {
> mutable int len;
Wow! That article must be from the early days of D. There is no
'mutable' in D (any more?).
> mutable bool len_done;
> const char* str;
> int length()
> {
> if (!len_done)
> {
> len = strlen(str);
> len_done = true;
That example is the concept of logical constness, where the object
computes some value as neeeded and caches the result for later use. The
member 'len' (and len_done) is modified even if the 'f' object below is
const. However, the example doesn't fit today's D because the function
should have been marked as 'const' as well:
int length() const {
// ...
}
In any case, there is no logical constness in D. (However, one can play
tricks like using casts. (Which may be undefined behavior, etc. etc.))
> }
> return len;
> }
> this(char* str) { this.str = str; }
> }
> const Foo f = Foo("hello");
> bar(f.length);
So, there is the 'const' object f and calling its length() member
function, which mutates two members of the object. As those mutations do
not change the value of the object, the object is considered still the
same. In other words, caching something about the object is considered
to not change that object. That's what is meant with logical const:
There has been changes but they did not change the state of the object.
Ali
Re: Const Variables
On Sunday, 3 April 2022 at 14:29:22 UTC, Paul Backus wrote:
On Sunday, 3 April 2022 at 13:50:28 UTC, Salih Dincer wrote:
Hi all,
Do you have a good example of how const variables actually
work?
So I'm not talking about system resources and programming
errors. I want to say it's good. Because if everything works
without it, why does it exist?
This is covered in the const FAQ:
https://dlang.org/articles/const-faq.html
The programs I write are not multithreaded. Also, I don't work
as a team. Thanks for the link but there is only the following
example:
```d
struct Foo
{
mutable int len;
mutable bool len_done;
const char* str;
int length()
{
if (!len_done)
{
len = strlen(str);
len_done = true;
}
return len;
}
this(char* str) { this.str = str; }
}
const Foo f = Foo("hello");
bar(f.length);
```
Moreover, I did not understand anything from the example in the
article :)
SDB@79
Re: arsd.minigui
On Sunday, 3 April 2022 at 17:10:48 UTC, Adam Ruppe wrote: On Sunday, 3 April 2022 at 16:58:03 UTC, JG wrote: [...] Which resizeImage did you use, from the imageresize module? What pain you have with it? Some of its settings take some tweaking. [...] Thank you very much for your quick reply. I see now I was doing something silly.
Re: arsd.minigui
On Sunday, 3 April 2022 at 16:58:03 UTC, JG wrote:
Hi,
I have an png image that I generate (via pdf via pdflatex) that
I want to scale and display in a widget. Is this possible via
something in arsd? I tried resizeImage but that doesn't seem to
do what I expect. Any suggestions?
Which resizeImage did you use, from the imageresize module? What
pain you have with it? Some of its settings take some tweaking.
Though in a widget, you can also stretch automatically on
Windows... actually XRender can do it too i believe but I never
implemented that. Maybe I should.
But imageresize should work with some experimentation. This is
how I did it in my image viewer application:
auto i = loadImageFromFile(arg);
auto size =
calculateSizeKeepingAspectRatio(i.width, i.height, maxWidth,
maxHeight);
if(size.width != i.width ||
size.height != i.height) {
i = imageResize(i,
size.width, size.height, null, 1.0, 0.6);
}
then pass that i to one of the minigui/simplediplay functions to
display.
arsd.minigui
Hi, I have an png image that I generate (via pdf via pdflatex) that I want to scale and display in a widget. Is this possible via something in arsd? I tried resizeImage but that doesn't seem to do what I expect. Any suggestions?
Re: Unit tests via DUB
On Saturday, 2 April 2022 at 11:53:12 UTC, alexanderzhirov wrote: I don't quite understand why compiling unit tests using DUB doesn't work. [...] Have a look here https://andre2007.github.io/d-tips/dub/application_template/ Kind regards Andre
Re: Const Variables
On Sunday, 3 April 2022 at 13:50:28 UTC, Salih Dincer wrote: Hi all, Do you have a good example of how const variables actually work? So I'm not talking about system resources and programming errors. I want to say it's good. Because if everything works without it, why does it exist? This is covered in the const FAQ: https://dlang.org/articles/const-faq.html
Const Variables
Hi all, Do you have a good example of how const variables actually work? So I'm not talking about system resources and programming errors. I want to say it's good. Because if everything works without it, why does it exist? Thanks, SDB@79
Re: Where I download Digital Mars C Preprocessor sppn.exe?
On Saturday, 2 April 2022 at 21:57:02 UTC, Marcone wrote: Where I download Digital Mars C Preprocessor sppn.exe? I need it to use ImportC it's part of the [DMC] toolchain. [DMC]: http://ftp.digitalmars.com/Digital_Mars_C++/Patch/dm857c.zip
Re: Where I download Digital Mars C Preprocessor sppn.exe?
On Saturday, 2 April 2022 at 23:40:39 UTC, Marcone wrote: ImportC is deprecated as everything in D is deprecated and abandoned. No link works, every download link is broken as no one cares. All D code is always full of bugs and needs to be corrected by the user before trying to run it, in order to realize that it wasted time. https://dlang.org/spec/importc.html ImportC is an interesting, and possibly useful feature..to a select few, but ALL will have to carry it. IMO...ImportC will be D's biggest mistake.
Re: Where I download Digital Mars C Preprocessor sppn.exe?
On 4/2/22 16:40, Marcone wrote: > ImportC is deprecated as everything in D is deprecated and abandoned. You're off a little: April Fool's was yesterday. :o) Ali
