On 11/1/21 1:49 PM, pascal111 wrote:

> Yes, I'm practicing doing things in low level style like standard C.

All you needed extra was to let the slice know about the new length:

import std.stdio;
import core.stdc.string;

void main() {
  char[] s="xyz".dup;
  strcpy(&s[0], "Hello World!");
  s = s.ptr[0..12];           // <-- Here
  writeln(s);
}

Now, the result is "correct" without dup:

Hello World!

The program is as incorrect as its C equivalent would be. ;)

Ali

On Monday, 1 November 2021 at 21:01:31 UTC, Ali Çehreli wrote:
> On 11/1/21 1:49 PM, pascal111 wrote:
>
> > Yes, I'm practicing doing things in low level style like
> standard C.
>
> All you needed extra was to let the slice know about the new length:
>
> import std.stdio;
> import core.stdc.string;
>
> void main() {
>   char[] s="xyz".dup;
>   strcpy(&s[0], "Hello World!");
>   s = s.ptr[0..12];           // <-- Here
>   writeln(s);
> }
>
> Now, the result is "correct" without dup:
>
> Hello World!
>
> The program is as incorrect as its C equivalent would be. ;)
>
> Ali

This can serve the style I want. It uses OOP style like C++ by putting a pointer as a property, but pointers themselves are low level.

On 11/1/21 2:01 PM, Ali Çehreli wrote:

> The program is as incorrect as its C equivalent would be. ;)

I wrote a cool function to make it easy to disregard memory safety:

import std.stdio;

auto assumedLength(S)(ref S slice) {
  struct LengthSetter {
    void opAssign(size_t length) {
      // Nooo! :)
      *cast(size_t*)(&slice) = length;
    }
  }

  return LengthSetter();
}

void main() {
  auto arr = [ 1, 2, 3 ];
  arr.assumedLength = 10;
  writeln(arr);
}

Joking aside, I liked the nested struct and its opAssign to mimic internal `arr.length = 42` syntax. (I know it involves a potentially expensive delegate but still...)

Ali

On 11/1/21 2:28 PM, pascal111 wrote:

> This can serve the style I want.

I am feeling funny right now and showing incorrect code. It's impossible to fit "Hello World!" in "xyz". As Steve said, don't do that. :)

> It uses OOP style like C++ by putting a
> pointer as a property,

D's slices are the equivalent of the following struct (showing for int):

struct __Slice__ {
  size_t length;
  int * ptr;
}

So, .ptr is simply a member variable. (Assigning to .length does some magic like allocating more memory in some cases; otherwise it is a member variable as well.)

> but pointers themselves are low level.

arr.ptr is as low as it gets: It is a pointer.

Ali

On Monday, 1 November 2021 at 21:32:21 UTC, Ali Çehreli wrote:
> On 11/1/21 2:01 PM, Ali Çehreli wrote:
>
> > The program is as incorrect as its C equivalent would be. ;)
>
> I wrote a cool function to make it easy to disregard memory safety:
>
> import std.stdio;
>
> auto assumedLength(S)(ref S slice) {
>   struct LengthSetter {
>     void opAssign(size_t length) {
>       // Nooo! :)
>       *cast(size_t*)(&slice) = length;
>     }
>   }
>
>   return LengthSetter();
> }
>
> void main() {
>   auto arr = [ 1, 2, 3 ];
>   arr.assumedLength = 10;
>   writeln(arr);
> }
>
> Joking aside, I liked the nested struct and its opAssign to mimic internal `arr.length = 42` syntax. (I know it involves a potentially expensive delegate but still...)
>
> Ali

This function seems smart and flexible and higher than my current level, I'll study it.

On Monday, 1 November 2021 at 21:37:59 UTC, Ali Çehreli wrote:
> On 11/1/21 2:28 PM, pascal111 wrote:
>
> > This can serve the style I want.
>
> I am feeling funny right now and showing incorrect code. It's impossible to fit "Hello World!" in "xyz". As Steve said, don't do that. :)
>
> > It uses OOP style like C++ by putting a
> > pointer as a property,
>
> D's slices are the equivalent of the following struct (showing for int):
>
> struct __Slice__ {
>   size_t length;
>   int * ptr;
> }
>
> So, .ptr is simply a member variable. (Assigning to .length does some magic like allocating more memory in some cases; otherwise it is a member variable as well.)
>
> > but pointers themselves are low level.
>
> arr.ptr is as low as it gets: It is a pointer.
>
> Ali

Anyway, I'm a beginner and any information is useful to me.