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digitalmars.D.learn - How to walk over two arrays by ref in beautyfull way?

reply vitalfadeev <vital.fadeev gmail.com> writes:
How to?

I plan scan First array with checkers:
[checker, checker, checker]

...and store result to Second array:
[0, 0, 1]

In next code 'r' not reference. But expected ref.

     import std.range : zip;

     foreach(checker, ref r; zip(checkers, result.set)) {
        r = checker();
     }

What is the best way for speed and beautyfull D code?
Jun 10 2019
parent reply vitalfadeev <vital.fadeev gmail.com> writes:
On Monday, 10 June 2019 at 07:41:40 UTC, vitalfadeev wrote:

 How to?

 I plan scan First array with checkers:
 [checker, checker, checker]

 ...and store result to Second array:
 [0, 0, 1]

 In next code 'r' not reference. But expected ref.

     import std.range : zip;

     foreach(checker, ref r; zip(checkers, result.set)) {
        r = checker();
     }

 What is the best way for speed and beautyfull D code?


Detailed:

      import std.range : zip;

      struct Result {
          byte[] set;
      }
      Result result;

      alias Callback = bool delegate();
      Callback[] checkers;


      foreach(checker, ref r; zip(checkers, result.set)) {
         r = checker();
      }
Jun 10 2019
parent reply vitalfadeev <vital.fadeev gmail.com> writes:
On Monday, 10 June 2019 at 07:45:42 UTC, vitalfadeev wrote:

 On Monday, 10 June 2019 at 07:41:40 UTC, vitalfadeev wrote:

 How to?

 I plan scan First array with checkers:
 [checker, checker, checker]

 ...and store result to Second array:
 [0, 0, 1]

 In next code 'r' not reference. But expected ref.

     import std.range : zip;

     foreach(checker, ref r; zip(checkers, result.set)) {
        r = checker();
     }

 What is the best way for speed and beautyfull D code?


 Detailed:


import std.range : zip;
import std.stdio : writeln, write;


struct Result {
     byte[] set;
}

alias Callback = bool function();


Callback[] checkers;
Result result;


bool false_cb() { return 0; }
bool true_cb() { return 1; }


void init() {
	checkers ~= &false_cb;
	checkers ~= &false_cb;
	checkers ~= &true_cb;

	result.set.length = checkers.length;
}


void check() {
     foreach(checker, ref r; zip(checkers, result.set)) {
         r = checker();
     }
}


void print() {
     foreach(r; result.set) {
         write(r, " ");
     }
     writeln();
}


void main() {
     init();
     check();
     print();
}



https://run.dlang.io/is/Plqcq5
Jun 10 2019
next sibling parent reply Anonymouse <zorael gmail.com> writes:
On Monday, 10 June 2019 at 08:02:18 UTC, vitalfadeev wrote:

 On Monday, 10 June 2019 at 07:45:42 UTC, vitalfadeev wrote:

 On Monday, 10 June 2019 at 07:41:40 UTC, vitalfadeev wrote:

 How to?

 I plan scan First array with checkers:
 [checker, checker, checker]

 ...and store result to Second array:
 [0, 0, 1]

 In next code 'r' not reference. But expected ref.

     import std.range : zip;

     foreach(checker, ref r; zip(checkers, result.set)) {
        r = checker();
     }






Replace zip with lockstep and your example works.

"zip is similar to lockstep, but lockstep doesn't bundle its 
elements and uses the opApply protocol. lockstep allows reference 
access to the elements in foreach iterations."

https://dlang.org/library/std/range/zip.html

"Function lockstep

Iterate multiple ranges in lockstep using a foreach loop. In 
contrast to zip it allows reference access to its elements."

https://dlang.org/library/std/range/lockstep.html
Jun 10 2019
parent vitalfadeev <vital.fadeev gmail.com> writes:
Thanks!

I happy!

You are really powerfull!
Jun 10 2019
prev sibling parent Russel Winder <russel winder.org.uk> writes:
On Mon, 2019-06-10 at 08:02 +0000, vitalfadeev via Digitalmars-d-learn
wrote:

[=E2=80=A6]

Perhaps I am missing something that is critical to the example, but I
rewrote the code as:

   import std.algorithm: map;
   import std.stdio: writeln;

   bool false_cb() { return false; }
   bool true_cb() { return true; }

   void main() {
       auto checkers =3D [&false_cb, &false_cb, &true_cb];
       auto result =3D map!(a =3D> a())(checkers);
       writeln(result);
   }

This avoids the assumption that 0 is false and 1 is true. Also it makes
use of D map which seems to me what is happening at the core of the
code =E2=80=93 using foreach and zip or lockstep just seems to be implement=
ing
map. But as I say, I may be missing something.

--=20
Russel.
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=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
Dr Russel Winder      t: +44 20 7585 2200
41 Buckmaster Road    m: +44 7770 465 077
London SW11 1EN, UK   w: www.russel.org.uk
Jun 10 2019