• h3r3tic <h3r3tic dev.null> Aug 19 2004
• Derek Parnell <derek psych.ward> Aug 19 2004
• h3r3tic <h3r3tic dev.null> Aug 19 2004
• Sha Chancellor <schancel pacific.net> Sep 26 2004
• h3r3tic <h3r3tic dev.null> Sep 26 2004
• "Walter" <newshound digitalmars.com> Aug 19 2004

h3r3tic <h3r3tic dev.null> writes:

just a short note:
now we can do:
(dmd 0.99)

int[] b = a[0..length-2];

where a is another array of int...


but isn't the 'length' ident redundant at all ? Python makes it implicit 
when the index is negative, so that a[0..-2] is a[0..length-2]. why dont 
we have it the same way ? it is very handy :)

Derek Parnell <derek psych.ward> writes:

On Fri, 20 Aug 2004 04:46:47 +0200, h3r3tic wrote:

 just a short note:
 now we can do:
 (dmd 0.99)
 
 int[] b = a[0..length-2];
 
 where a is another array of int...
 
 but isn't the 'length' ident redundant at all ? Python makes it implicit 
 when the index is negative, so that a[0..-2] is a[0..length-2]. why dont 
 we have it the same way ? it is very handy :)


Its more explicit; tells the reader what we were intending to do.

It helps trap some mistakes...

   int x,y;

   y = calc_size(a, z);
   . . . 
   x = y - 1;

   b = a[1..x];

But if for some reason 'y' was zero or lower, this would be an error. It
might not go detected if -ve values were allowed in slices.

-- 
Derek
Melbourne, Australia
20/Aug/04 12:50:38 PM

h3r3tic <h3r3tic dev.null> writes:

Derek Parnell wrote:
 Its more explicit; tells the reader what we were intending to do.
 
 It helps trap some mistakes...
 
    int x,y;
 
    y = calc_size(a, z);
    . . . 
    x = y - 1;
 
    b = a[1..x];
 
 But if for some reason 'y' was zero or lower, this would be an error. It
 might not go detected if -ve values were allowed in slices.
 


ok, i get ur point. thanks :]

how about another thing though ? in python (yea, again ;]) i can say 
x[0:10:2] and that will create a sliced array with indexes 0, 2, 4, 6, 
8, basically changing the stride of the slice. how bout that ? could be 
[a..b:c] or just [a..b..c] but i'd prefer the former

Sha Chancellor <schancel pacific.net> writes:

In article <cg3rb4$2qij$1 digitaldaemon.com>,
 h3r3tic <h3r3tic dev.null> wrote:

 ok, i get ur point. thanks :]
 
 how about another thing though ? in python (yea, again ;]) i can say 
 x[0:10:2] and that will create a sliced array with indexes 0, 2, 4, 6, 
 8, basically changing the stride of the slice. how bout that ? could be 
 [a..b:c] or just [a..b..c] but i'd prefer the former


Slices return a pointer to a contiguous block of memory located inside 
the array you sliced.  It doesn't allocated any new memory, it's just a 
pointer and a length.   At least that's my understanding.

h3r3tic <h3r3tic dev.null> writes:

Sha Chancellor wrote:
 In article <cg3rb4$2qij$1 digitaldaemon.com>,
  h3r3tic <h3r3tic dev.null> wrote:
 
 
ok, i get ur point. thanks :]

how about another thing though ? in python (yea, again ;]) i can say 
x[0:10:2] and that will create a sliced array with indexes 0, 2, 4, 6, 
8, basically changing the stride of the slice. how bout that ? could be 
[a..b:c] or just [a..b..c] but i'd prefer the former


 
 Slices return a pointer to a contiguous block of memory located inside 
 the array you sliced.  It doesn't allocated any new memory, it's just a 
 pointer and a length.   At least that's my understanding.


Sure, but there was a discussion going around some time earlier 
(relative to my old post) proposing interleaved arrays (even for 
multidimensional arrays) and this would just fit nicely with that concept.

"Walter" <newshound digitalmars.com> writes:

"h3r3tic" <h3r3tic dev.null> wrote in message
news:cg3omi$2p2q$1 digitaldaemon.com...
 just a short note:
 now we can do:
 (dmd 0.99)

 int[] b = a[0..length-2];

 where a is another array of int...


 but isn't the 'length' ident redundant at all ? Python makes it implicit
 when the index is negative, so that a[0..-2] is a[0..length-2]. why dont
 we have it the same way ? it is very handy :)


This is a common request. One reason it isn't done is it requires a runtime
check, and people really like their arrays to be fast!