digitalmars.D.learn - Shortest way to allocate an array and initialize it with a specific

Adel Mamin (5/5) Jun 10 2015 ubyte[5] a = 0xAA; // Fine. Five 0xAA bytes.

Low Functioning (2/7) Jun 10 2015 Assign void, then assign whatever?
Michael Coulombe (3/8) Jun 10 2015 Probably:
=?UTF-8?B?QWxpIMOHZWhyZWxp?= (12/17) Jun 10 2015 Another option:

"Per =?UTF-8?B?Tm9yZGzDtnci?= <per.nordlow gmail.com> (5/10) Jun 11 2015 Is

"Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm gmx.net> (4/15) Jun 11 2015 Yes, it uses `uninitializedArray()` if the length is known (which
weaselcat (3/10) Jun 11 2015 just an fyi, gdc optimizes this away(looks like it overwrites the

Daniel =?UTF-8?B?S296w6Fr?= via Digitalmars-d-learn (12/17) Jun 11 2015 On Wed, 10 Jun 2015 20:22:17 +0000

"Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm gmx.net> (2/20) Jun 11 2015 I like this one :-)

Daniel =?UTF-8?B?S296w6Fr?= via Digitalmars-d-learn (4/29) Jun 11 2015 small enhancment:

Steven Schveighoffer (5/34) Jun 11 2015 import std.typecons;

"Adel Mamin" <adel mm.st> writes:

ubyte[5] a = 0xAA; // Fine. Five 0xAA bytes.
auto a2 = new ubyte[5]; // Fine. Five 0 bytes.
Now, let's say, I want to allocate an array of a size, derived at 
run time, and initialize it to some non-zero value at the same 
time. What would be the shortest way of doing it?

Jun 10 2015

"Low Functioning" <nathan.judge gmail.com> writes:

On Wednesday, 10 June 2015 at 20:22:18 UTC, Adel Mamin wrote:
 ubyte[5] a = 0xAA; // Fine. Five 0xAA bytes.
 auto a2 = new ubyte[5]; // Fine. Five 0 bytes.
 Now, let's say, I want to allocate an array of a size, derived 
 at run time, and initialize it to some non-zero value at the 
 same time. What would be the shortest way of doing it?

Assign void, then assign whatever?

Jun 10 2015

"Michael Coulombe" <kirsybuu gmail.com> writes:

On Wednesday, 10 June 2015 at 20:22:18 UTC, Adel Mamin wrote:
 ubyte[5] a = 0xAA; // Fine. Five 0xAA bytes.
 auto a2 = new ubyte[5]; // Fine. Five 0 bytes.
 Now, let's say, I want to allocate an array of a size, derived 
 at run time, and initialize it to some non-zero value at the 
 same time. What would be the shortest way of doing it?

Probably:

auto a2 = value.repeat(size).array;

Jun 10 2015

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

On 06/10/2015 01:22 PM, Adel Mamin wrote:
 ubyte[5] a = 0xAA; // Fine. Five 0xAA bytes.
 auto a2 = new ubyte[5]; // Fine. Five 0 bytes.
 Now, let's say, I want to allocate an array of a size, derived at run
 time, and initialize it to some non-zero value at the same time. What
 would be the shortest way of doing it?

Another option:

void main()
{
     auto a2 = new ubyte[5];
     a2[] = 0xAA;    // <-- Assign to "all elements"

     /* Alternative syntax:
      *
      *    auto a2 = new ubyte[](5);
      */
}

Ali

Jun 10 2015

"Per =?UTF-8?B?Tm9yZGzDtnci?= <per.nordlow gmail.com> writes:

On Wednesday, 10 June 2015 at 22:03:52 UTC, Ali Çehreli wrote:
 Another option:

 void main()
 {
     auto a2 = new ubyte[5];

But this causes an extra zero-initialization of a2.

     a2[] = 0xAA;    // <-- Assign to "all elements"

Is

     auto a2 = value.repeat(size).array;

better in this regard?

Jun 11 2015

"Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm gmx.net> writes:

On Thursday, 11 June 2015 at 07:57:47 UTC, Per Nordlöw wrote:
 On Wednesday, 10 June 2015 at 22:03:52 UTC, Ali Çehreli wrote:
 Another option:

 void main()
 {
    auto a2 = new ubyte[5];

 But this causes an extra zero-initialization of a2.

    a2[] = 0xAA;    // <-- Assign to "all elements"

 Is

     auto a2 = value.repeat(size).array;

 better in this regard?

Yes, it uses `uninitializedArray()` if the length is known (which 
it is for `repeat()`):
https://github.com/D-Programming-Language/phobos/blob/master/std/array.d#L111

Jun 11 2015

"weaselcat" <weaselcat gmail.com> writes:

On Thursday, 11 June 2015 at 07:57:47 UTC, Per Nordlöw wrote:
 On Wednesday, 10 June 2015 at 22:03:52 UTC, Ali Çehreli wrote:
 Another option:

 void main()
 {
    auto a2 = new ubyte[5];

 But this causes an extra zero-initialization of a2.

just an fyi, gdc optimizes this away(looks like it overwrites the 
typeinfo,) ldc does not.

Jun 11 2015

Daniel =?UTF-8?B?S296w6Fr?= via Digitalmars-d-learn writes:

On Wed, 10 Jun 2015 20:22:17 +0000
Adel Mamin via Digitalmars-d-learn <digitalmars-d-learn puremagic.com>
wrote:

 ubyte[5] a = 0xAA; // Fine. Five 0xAA bytes.
 auto a2 = new ubyte[5]; // Fine. Five 0 bytes.
 Now, let's say, I want to allocate an array of a size, derived at 
 run time, and initialize it to some non-zero value at the same 
 time. What would be the shortest way of doing it?

import std.stdio;

struct Ubyte(ubyte defval) {
    ubyte v = defval;
    alias v this;
}

void main() {
	auto a2 = new Ubyte!(0xAA)[5];
	writeln(a2);
}

Jun 11 2015

"Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm gmx.net> writes:

On Thursday, 11 June 2015 at 08:33:46 UTC, Daniel Kozák wrote:
 On Wed, 10 Jun 2015 20:22:17 +0000
 Adel Mamin via Digitalmars-d-learn 
 <digitalmars-d-learn puremagic.com>
 wrote:

 ubyte[5] a = 0xAA; // Fine. Five 0xAA bytes.
 auto a2 = new ubyte[5]; // Fine. Five 0 bytes.
 Now, let's say, I want to allocate an array of a size, derived 
 at run time, and initialize it to some non-zero value at the 
 same time. What would be the shortest way of doing it?

 import std.stdio;

 struct Ubyte(ubyte defval) {
     ubyte v = defval;
     alias v this;
 }

 void main() {
 	auto a2 = new Ubyte!(0xAA)[5];
 	writeln(a2);
 }

I like this one :-)

Jun 11 2015

Daniel =?UTF-8?B?S296w6Fr?= via Digitalmars-d-learn writes:

On Thu, 11 Jun 2015 11:43:25 +0000
via Digitalmars-d-learn <digitalmars-d-learn puremagic.com> wrote:

 On Thursday, 11 June 2015 at 08:33:46 UTC, Daniel Kozák wrote:
 On Wed, 10 Jun 2015 20:22:17 +0000
 Adel Mamin via Digitalmars-d-learn 
 <digitalmars-d-learn puremagic.com>
 wrote:

 ubyte[5] a = 0xAA; // Fine. Five 0xAA bytes.
 auto a2 = new ubyte[5]; // Fine. Five 0 bytes.
 Now, let's say, I want to allocate an array of a size, derived 
 at run time, and initialize it to some non-zero value at the 
 same time. What would be the shortest way of doing it?

 import std.stdio;

 struct Ubyte(ubyte defval) {
     ubyte v = defval;
     alias v this;
 }

 void main() {
 	auto a2 = new Ubyte!(0xAA)[5];
 	writeln(a2);
 }

 
 I like this one :-)

small enhancment:
struct Ubyte(ubyte defval = 0)

Jun 11 2015

Steven Schveighoffer <schveiguy yahoo.com> writes:

On 6/11/15 7:51 AM, Daniel Kozák via Digitalmars-d-learn wrote:
 On Thu, 11 Jun 2015 11:43:25 +0000
 via Digitalmars-d-learn <digitalmars-d-learn puremagic.com> wrote:

 On Thursday, 11 June 2015 at 08:33:46 UTC, Daniel Kozák wrote:
 On Wed, 10 Jun 2015 20:22:17 +0000
 Adel Mamin via Digitalmars-d-learn
 <digitalmars-d-learn puremagic.com>
 wrote:

 ubyte[5] a = 0xAA; // Fine. Five 0xAA bytes.
 auto a2 = new ubyte[5]; // Fine. Five 0 bytes.
 Now, let's say, I want to allocate an array of a size, derived
 at run time, and initialize it to some non-zero value at the
 same time. What would be the shortest way of doing it?

 import std.stdio;

 struct Ubyte(ubyte defval) {
      ubyte v = defval;
      alias v this;
 }

 void main() {
 	auto a2 = new Ubyte!(0xAA)[5];
 	writeln(a2);
 }

 I like this one :-)

 small enhancment:
 struct Ubyte(ubyte defval = 0)

import std.typecons;

alias Ubyte(ubyte defval = 0) = Typedef!(ubyte, defval);

I personally like the range solution the best, it has the most flexibility.

-Steve

Jun 11 2015

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digitalmars.D.learn - Shortest way to allocate an array and initialize it with a specific