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digitalmars.D.learn - What does it mean: buffer[0 .. kSize] = input[index .. (index + Size)];

reply "t0mek" <t0mek com.com.com.com.com> writes:
Hello,
I found some code in D and I am wondering what does it mean:
buffer[0 .. Size] = input[index .. (index + Size)];

I understand it can be written like this:
for (i=0; i<Size; i++) buffer[i]=input[i+index];
But...
1) does it allocate space for buffer?
2) if buffer has already some data- will be zeroed?
3) if there is no enough date (less then Size) in input will there be an 
exception or will be copied what already is in the array?

Regards,
t0mek
Jul 25 2008
parent reply "Koroskin Denis" <2korden gmail.com> writes:
On Fri, 25 Jul 2008 12:50:36 +0400, t0mek <t0mek com.com.com.com.com>  
wrote:


 Hello,
 I found some code in D and I am wondering what does it mean:
 buffer[0 .. Size] = input[index .. (index + Size)];

 I understand it can be written like this:
 for (i=0; i<Size; i++) buffer[i]=input[i+index];
 But...
 1) does it allocate space for buffer?
 2) if buffer has already some data- will be zeroed?
 3) if there is no enough date (less then Size) in input will there be an  
 exception or will be copied what already is in the array?

 Regards,
 t0mek




It is *exactly* the same (however, a memcpy could be used under the hood),  
i.e.
- there is no allocation
- data will be overwritten
- an OutOfBounds exception will be thrown if array is not large enough
Jul 25 2008
next sibling parent "t0mek" <t0mek com.com.com.com.com> writes:
 It is *exactly* the same (however, a memcpy could be used under the hood), 
 i.e.
 - there is no allocation
 - data will be overwritten
 - an OutOfBounds exception will be thrown if array is not large enough



Thanks!

Regards,
t0mek
Jul 25 2008
prev sibling next sibling parent bearophile <bearophileHUGS lycos.com> writes:
Koroskin Denis:

 - an OutOfBounds exception will be thrown if array is not large enough



If compiled in -release mode no exception is thrown, I think.

Bye,
bearophile
Jul 25 2008
prev sibling parent BCS <ao pathlink.com> writes:
Reply to Koroskin,


 On Fri, 25 Jul 2008 12:50:36 +0400, t0mek <t0mek com.com.com.com.com>
 wrote:
 

 Hello,
 I found some code in D and I am wondering what does it mean:
 buffer[0 .. Size] = input[index .. (index + Size)];
 I understand it can be written like this:
 for (i=0; i<Size; i++) buffer[i]=input[i+index];
 But...
 1) does it allocate space for buffer?
 2) if buffer has already some data- will be zeroed?
 3) if there is no enough date (less then Size) in input will there be
 an
 exception or will be copied what already is in the array?
 Regards,
 t0mek



 hood),



Not /exaltly/ the same, because IIRC the exception will be thrown before 
any copy takes place and the for loop will copy to the end of one of the 
buffers and then throw. 

Most of the time the difference isn't important, but...



 i.e.
 - there is no allocation
 - data will be overwritten
 - an OutOfBounds exception will be thrown if array is not large enough
Jul 25 2008