Re: Why do we have Dmain?
On Friday, 22 October 2021 at 07:00:25 UTC, Mike Parker wrote: [...] Thank you for such a clear explanation Mike and for a quick reply!
Why do we have Dmain?
I am not a compiler expert, but I genuinely would like to know why we have Dmain. I've been looking at the generated assembly code recently and noticed the _Dmain function. I didn't notice it before. Then there is main, where Dmain is called. Why is that?
Extract base type of any array?
How can I get the base type of any
(multidimensional/static/dynamic/associative) array?
Example:
```
void main() {
int[][] intArr;
double[4][] doubleArr;
string[string][] strArr;
intArr.example; // T = int
doubleArr.example; // T = double
strArr.example; // T = string
}
void example(T)(<...> data) {
// extract the base of data (inside func's body or in <...>)
// preferably, T must become data's base type
}
```
Re: A way to mixin during runtime?
On Friday, 27 August 2021 at 09:51:46 UTC, Mathias LANG wrote: On Friday, 27 August 2021 at 06:52:10 UTC, Kirill wrote: Is there a way to do mixin or similar during runtime? I'm trying to read a csv file and extract data types. Any ideas on how this should be approached in D are greatly appreciated. You cannot mixin at runtime. However, it is fairly easy to map a finite and CT-know set of argument to runtime arguments via `static foreach`. Could you give us example of the content of your CSV file and what you are trying to do ? Each csv file will be different. For example: ``` name;surname;age;grade Alex;Wong;18;87 John;Doe;19;65 Alice;Doe;18;73 etc... ``` I'd like to extract the data types automatically. For instance, if using tuples: ``` Tuple!(string, string, int, int) ... ``` instead I'd like to have: ``` auto mytuple = read_csv(path); // returns Tuple!(string, string, int, int)[] ```
A way to mixin during runtime?
Is there a way to do mixin or similar during runtime? I'm trying to read a csv file and extract data types. Any ideas on how this should be approached in D are greatly appreciated.
Re: How do I check if a variable is a multidimensional (2D) array?
On Monday, 12 July 2021 at 05:08:29 UTC, jfondren wrote:
On Monday, 12 July 2021 at 04:25:00 UTC, Kirill wrote:
I know there is isArray!T and similar functionality in
std.traits. But I couldn't find the functionality that can
help me check if I have a multidimensional array. Is there
any? How do I create my own?
Thanks in advance.
from https://github.com/PhilippeSigaud/D-templates-tutorial
```d
template rank(T) {
static if (is(T t == U[], U))
enum size_t rank = 1 + rank!(U);
else
enum size_t rank = 0;
}
unittest {
int a;
int[] b;
int[][] c;
assert(rank!(typeof(a)) == 0);
assert(rank!(typeof(b)) == 1);
assert(rank!(typeof(c)) == 2);
}
```
as an example of a recursive template. There's also an
implementation for ranges.
Thanks!
How do I check if a variable is a multidimensional (2D) array?
I know there is isArray!T and similar functionality in std.traits. But I couldn't find the functionality that can help me check if I have a multidimensional array. Is there any? How do I create my own? Thanks in advance.
Printing Tuple!(...)[] using for loop?
I have a `Tuple!(string, ..., string)[] data` that I would like
to print out:
`a b c`
`1 2 3`
`4 5 6`
Furthermore, I want to be able to print any N rows and M
columns of that table. For instance:
`b c`
`2 3`
or
`1 2 3`
`4 5 6`
I am using for loops for that:
// inside some function(rows, cols):
immutable startFromRow = ...;
immutable endWithRow = ...;
immutable startFromCol = ...;
immutable endWithCol = ...;
// print data
for(size_t i = startFromRow; i < endWithRow; i++) {
for(size_t j = startFromCol; j < endWithCol; j++) {
writef("%s", data[i][j]);
}
writef("\n");
}
And the compiler puts out the following:
`Error: variable 'j' cannot be read at compile time`
I tried `data[i].expand[j]`, but the same error occurs anyway.
I have two questions:
1. How do I print the contents of a Tuple using for loops? Or any
other method?
2. What am I missing? How does it actually work under the hood?
Thanks in advance. Any help is greatly appreciated.
Re: Parallel foreach iteration with Associative Arrays
On Saturday, 17 April 2021 at 02:14:50 UTC, Paul Backus wrote:
`parallel` requires a range [1], and an associative array is
not a range. To get a range of an AA's keys and values, you can
use the method `.byKeyValue`:
foreach (pair; parallel(example.byKeyValue)) {
writeln(pair.key, ": ", pair.value);
}
If you're confused about what a "range" is, the short answer is
that it's kind of like an iterator. For the long answer, check
out Andrei Alexandrescu's article "On Iteration" [2], or the
"Ranges" chapter of Ali Çehreli's "Programming in D" [3].
[1]
https://phobos.dpldocs.info/std.parallelism.TaskPool.parallel.2.html
[2] https://www.informit.com/articles/printerfriendly/1407357
[3] http://ddili.org/ders/d.en/ranges.html
That worked! Thanks you!
Parallel foreach iteration with Associative Arrays
I'd like to iterate over an associative array and output it's key
and value using parallel from std.parallelism.
But I get an error message: ParallelForeach!(int[string]) error
instantiating.
My code:
auto example = ["apples": 100, "orange": 250, "banana": 175];
foreach(key, value; parallel(example)) { writeln(key, ": ",
value); }
What am I doing wrong?
Thanks in advance.
Re: Tool to measure the time a function takes to execute?
On Monday, 28 December 2020 at 07:00:59 UTC, Ali Çehreli wrote: On 12/27/20 10:24 PM, Kirill wrote: Hello, is there a tool to measure the execution time of a function in D? Can the GC do it? StopWatch and benchmark(): https://dlang.org/phobos/std_datetime.html Ali Thanks Ali! That's exactly what I needed.
Tool to measure the time a function takes to execute?
Hello, is there a tool to measure the execution time of a function in D? Can the GC do it?
Re: How do I statically build a project using DUB?
On Saturday, 29 August 2020 at 12:06:38 UTC, Andre Pany wrote: On Saturday, 29 August 2020 at 11:27:28 UTC, Kirill wrote: I need a stand-alone executable that does not require the user to install any libraries on their computer. Everything should be packed into the executable. I understand that I need to statically link all of the libraries I use in my project, but how do I do this? What do I need to add to dub.json file? What compiler flags do I need to use? Thanks in advance. This highly depends on your actual project: - which 3rd party dependencies do you have - are these dependencies d source code only or wrapping C libraries - is the c source code of your dependencies available and you are able to create a static library of them - does the license of the c dependencies allows static linking Kind regards Andre I am trying to link the GTK library. I have the GTK Runtime installed on Windows 10 pc. Do I need to build the static GTK library from the source? Then how do I tell DUB to include that library?
How do I statically build a project using DUB?
I need a stand-alone executable that does not require the user to install any libraries on their computer. Everything should be packed into the executable. I understand that I need to statically link all of the libraries I use in my project, but how do I do this? What do I need to add to dub.json file? What compiler flags do I need to use? Thanks in advance.
Re: Translating C headers to D: How do I compile it?
On Sunday, 28 June 2020 at 05:13:32 UTC, Mike Parker wrote: On Sunday, 28 June 2020 at 04:59:12 UTC, Kirill wrote: something.d: module something; int add(int a, int b); This should be extern(C) int add(int a, int b). The extern(C) tells the D compiler to use the standard C calling convention when calling that function. Thanks! It all works now! 'extern(C)' is what was missing.
Translating C headers to D: How do I compile it?
Hello. I am learning how to translate C headers to D. But how do
I compile it? I am stuck with this.
I have 4 files in the same directory: main.d, something.d,
some.h, some.c
some.h:
//header guards
int add(int a, int b);
some.c:
#include "some.h"
int add(int a, int b) { return a+b; }
something.d:
module something;
int add(int a, int b);
main.d:
import std.stdio: writeln;
import something;
void main() { writeln("5+7=", add(5, 7); }
How do I compile this correctly?
Thank you for your time.
Re: Why are class variables public, when marked by the 'private' keyword?
On Saturday, 21 March 2020 at 04:58:32 UTC, Mike Parker wrote: In D, the unit of encapsulation is the module. So private means "private to the module", i.e., private members are accessible within the same module. If ID were in a different module from main, you would see an error. Indeed, I read something like this somewhere... It makes sense to me now! Thank you!
Why are class variables public, when marked by the 'private' keyword?
I was playing around with visibility attributes in D. I created a
class with private variables. Then I tried to access those
variables through the class object. It compiled without any
errors. However, ...
Shouldn't the compiler output an error for trying to access
private members of a class? Do I get something wrong?
Here is the code:
import std.stdio;
class ID {
public:
int id = 3849493;
private:
string name = "Julia";
int age = 17;
};
void main() {
ID p = new ID();
writeln(p.name, " ", p.age, " ", p.id);
}
Re: practicality of empirical cache optimization in D vs C++
I would also be curious to see projects in D that involved cache optimization.
practicality of empirical cache optimization in D vs C++
Dear D community (and specifically experts on cache optimization), I'm a C++ programmer and was waiting for a while to do a project in D. I'd like to build a cache-optimized decision tree forest library, and I'm debating between D and C++. I'd like to make it similar to atlas, spiral, or other libraries that partially use static optimization with recompilation and meta-programming to cache optimize the code for a specific architecture (specifically the latest xeons / xeon phi). Given D's compile speed and meta-programming, it should be a good fit. The problem that I might encounter is that C++ has a lot more information on the topic, which might be significant bottleneck given I'm just learning cache optimization (from a few papers and what every programmer should know about memory). From my understanding, cache optimization mostly involves breaking data and loops into segments that fit in cache, and making sure that commonly used variables (for example sum in sum+=i) stay in cache. Most of this should be solved by statically defining sizes and paddings of blocks to be used for caching. It's more related to low level -- C, from my understanding. Are there any hidden stones? The other question is how mature is the compiler in terms of optimizing for cache comparing to C++? I think gnu C++ does a few tricks to optimize for cache and there are ways to tweak cache line alignment. My knowledge on the subject is not yet concrete and limited but I hope this gave an idea of what I'm looking for and you can recommend me a good direction to take. Best regards, --Kirill
