I am trying to get rid of the first item of an array, so I am trying to figure it out what is the best way.  Right I I thought of this,

char[][] a;
a[0] = "a";
a[1] = "b";
a[2] = "c";
a[3] = "d";

so if I want to get rid of the first one, I do

a = a.reverse
a.length = a.length - 1;
a = a.reverse;

But now I am thinking that what if the array is huge.  So, what does array.reverse really does?

thanks,

josé

jicman wrote:
> I am trying to get rid of the first item of an array, so I am trying to figure it out what is the best way.  Right I I thought of this,
> 
> char[][] a;
> a[0] = "a";
> a[1] = "b";
> a[2] = "c";
> a[3] = "d";
> 
> so if I want to get rid of the first one, I do
> 
> a = a.reverse
> a.length = a.length - 1;
> a = a.reverse;
> 
> But now I am thinking that what if the array is huge.  So, what does array.reverse really does?
> 
> thanks,
> 
> josé
> 
> 

For one thing, it does it in-place, so you can just "a.reverse;" instead of "a = a.reverse;".

For another, to get rid of the first array element, I suggest "a = a[1..$]", which I would expect to be faster.

As to your question, I don't really know. Have a look at dmd\src\phobos\internal\adi.d, which has the code.

Deewiant says...
>
>jicman wrote:
>> I am trying to get rid of the first item of an array, so I am trying to figure it out what is the best way.  Right I I thought of this,
>> 
>> char[][] a;
>> a[0] = "a";
>> a[1] = "b";
>> a[2] = "c";
>> a[3] = "d";
>> 
>> so if I want to get rid of the first one, I do
>> 
>> a = a.reverse
>> a.length = a.length - 1;
>> a = a.reverse;
>> 
>> But now I am thinking that what if the array is huge.  So, what does array.reverse really does?
>> 
>> thanks,
>> 
>> josé
>> 
>> 
>
>For one thing, it does it in-place, so you can just "a.reverse;" instead of "a = a.reverse;".
>
>For another, to get rid of the first array element, I suggest "a = a[1..$]", which I would expect to be faster.

Yeah...  This one would be much faster... :-)  I had forgotten about this. Gosh, and I even used it a few months back... Read The Great Manual. :-)

Thanks.

>As to your question, I don't really know. Have a look at dmd\src\phobos\internal\adi.d, which has the code.

In article <e0jrkd$2ou$1@digitaldaemon.com>, Deewiant says...

>For another, to get rid of the first array element, I suggest "a = a[1..$]", which I would expect to be faster.
>


watch out for this though



int[] a = [1, 2, ..stuff...]
int[] b = a;

b = b[1..$];

assert(b[0] == a[0]);  //fails because only where b points to is changed.



somthing like this is needed to change the contents



foreach(int i, int j; a[1..$])
b[i] = j;