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digitalmars.D.learn - clear array

reply "Damian" <damianroyday gmail.com> writes:
I know this is a bit of a dumb question and I have searched and 
not
found anything concrete surprisingly :/

Does D have a built-in way to clear arrays dynamic and static?
I don't want to iterate over every element and set a default 
value.

In C++ I would just use memset, I don't know if I should be using
this for D?
Oct 15 2012
next sibling parent Andrej Mitrovic <andrej.mitrovich gmail.com> writes:
On 10/16/12, Damian <damianroyday gmail.com> wrote:

 Does D have a built-in way to clear arrays dynamic and static?


clear(arr).
arr.clear() should work too.
Oct 15 2012
prev sibling next sibling parent "Adam D. Ruppe" <destructionator gmail.com> writes:
On Tuesday, 16 October 2012 at 00:33:04 UTC, Damian wrote:

 In C++ I would just use memset, I don't know if I should be 
 using this for D?


The direct D analog to memset is:

int[] arr;
arr[] = 0; // or whatever


You can assign a value to a whole slice in a single go. arr[] 
means return a slice of the entire array. You can also do a 
range: arr[0 .. 4] = 0;, though, of course, you don't want to go 
out of bounds then.

I believe arr[] = 0 actually compiles as memset, but however it 
is implemented, it does the same thing.


Note that this sets the content, but leaves the length the same. 
If you want to get rid of it all, you can just assign null:

arr = null;
assert(arr.length == 0);
Oct 15 2012
prev sibling next sibling parent reply "Jonathan M Davis" <jmdavisProg gmx.com> writes:
On Tuesday, October 16, 2012 02:37:52 Andrej Mitrovic wrote:

 On 10/16/12, Damian <damianroyday gmail.com> wrote:

 Does D have a built-in way to clear arrays dynamic and static?


 
 clear(arr).
 arr.clear() should work too.


Use destroy, not clear. clear is now an alias for clear and should be going 
away eventually. There were too many problems with the ambiguity of the name
clear, so it was renamed.

- Jonathan M Davis
Oct 15 2012
parent reply "Damian" <damianroyday gmail.com> writes:
On Tuesday, 16 October 2012 at 00:44:15 UTC, Jonathan M Davis 
wrote:

 On Tuesday, October 16, 2012 02:37:52 Andrej Mitrovic wrote:

 On 10/16/12, Damian <damianroyday gmail.com> wrote:

 Does D have a built-in way to clear arrays dynamic and 
 static?


 
 clear(arr).
 arr.clear() should work too.


 Use destroy, not clear. clear is now an alias for clear and 
 should be going
 away eventually. There were too many problems with the 
 ambiguity of the name
 clear, so it was renamed.

 - Jonathan M Davis


destroy and clear work nicely, except when using large arrays dmd 
is taking quite a while to compile

int[1000][1000] arr;
destroy(arr);
Oct 15 2012
parent "bearophile" <bearophileHUGS lycos.com> writes:
Damian:


 destroy and clear work nicely, except when using large arrays 
 dmd is taking quite a while to compile

 int[1000][1000] arr;
 destroy(arr);


Unfortunately currently DMD/druntime is not designed to handle 
large fixed-sized arrays well, in general (large static floating 
point or char 2D arrays are the worst case). In such cases you 
sometimes have to use a dynamic array, or sometimes a little more 
efficiently a fixed sized array of dynamic arrays. In Bugzilla 
there are two ore more bug entries that ask for speeder 
compilations or better handling of such large fixed-sized arrays.

My dmd isn't even running the program that "int[1000][1000] arr;" 
array inside the main, I think I have to increase stack size.

Maybe you have found another case where dmd or its druntime are 
not well optimized, I have filed it in Bugzilla for you:

http://d.puremagic.com/issues/show_bug.cgi?id=8828

See there for more info.

Bye,
bearophile
Oct 15 2012
prev sibling parent reply "H. S. Teoh" <hsteoh quickfur.ath.cx> writes:
On Tue, Oct 16, 2012 at 02:33:03AM +0200, Damian wrote:

 I know this is a bit of a dumb question and I have searched and not
 found anything concrete surprisingly :/
 
 Does D have a built-in way to clear arrays dynamic and static?
 I don't want to iterate over every element and set a default value.
 
 In C++ I would just use memset, I don't know if I should be using
 this for D?


What about:

	import std.algorithm;
	void main() {
		int[] arr = [1,2,3,4];

		fill(arr, 0);
		writeln(arr);	// should print [0,0,0,0]
	}

?


T

-- 
My program has no bugs! Only undocumented features...
Oct 15 2012
parent "Damian" <damianroyday gmail.com> writes:
On Tuesday, 16 October 2012 at 00:47:44 UTC, H. S. Teoh wrote:

 On Tue, Oct 16, 2012 at 02:33:03AM +0200, Damian wrote:

 I know this is a bit of a dumb question and I have searched 
 and not
 found anything concrete surprisingly :/
 
 Does D have a built-in way to clear arrays dynamic and static?
 I don't want to iterate over every element and set a default 
 value.
 
 In C++ I would just use memset, I don't know if I should be 
 using
 this for D?


 What about:

 	import std.algorithm;
 	void main() {
 		int[] arr = [1,2,3,4];

 		fill(arr, 0);
 		writeln(arr);	// should print [0,0,0,0]
 	}

 ?


 T


This does not handle multi-dimensional arrays
Oct 15 2012