• Omid (10/10) Dec 30 2012 Hi, I am new to D and would like to know if there is any built in
• bearophile (14/20) Dec 30 2012 This gives a range, not an array, so if you want an array, you
• Omid (3/25) Dec 30 2012 Thanks, though I didn't understand a word you said:). I should
• bearophile (21/22) Dec 30 2012 This code works with the latest beta compiler:
• Omid (4/25) Dec 31 2012 Thanks again. I started learning std.array and I should say it
• Omid (2/3) Dec 31 2012 Actually, std.array and std.range both.

"Omid" <mehdioa gmail.com> writes:

Hi, I am new to D and would like to know if there is any built in 
feature for accessing a subarray (uni or multi dimensional) of an 
array. For example let

arr = [[1,2,3,4,5,6],[7,8,9,10,11,12],[13,14,15,16,17,18]]

I want to obtain a subarray like

assert(arr[][0] == [1,7,13]);
assert(arr[1][] == [7,8,9,10,11,12];
assert(arr[0,2][1] == [2,14]);
assert(arr[0,2][0..3,5] == [[1,2,3,6],[13,14,15,18]]);

Thank you.

"bearophile" <bearophileHUGS lycos.com> writes:

Omid:

 arr = [[1,2,3,4,5,6],[7,8,9,10,11,12],[13,14,15,16,17,18]]

 I want to obtain a subarray like

 assert(arr[][0] == [1,7,13]);

This gives a range, not an array, so if you want an array, you 
have to call std.array.array later:

http://dlang.org/phobos/std_range.html#transversal


 assert(arr[1][] == [7,8,9,10,11,12];

Just use array[1]. Or array[1].dup is you want a copy.


 assert(arr[0,2][1] == [2,14]);

Enumerated indexes are not supported, so you need a iota + filter 
+ transversal + array.


 assert(arr[0,2][0..3,5] == [[1,2,3,6],[13,14,15,18]]);

This requires a iota + filter + chain + array, or something like 
that.

If you don't want to do all this, you have to write your slicing 
and dicing array struct :-( Someday it will probably be present 
in Phobos.

Bye,
bearophile

"Omid" <mehdioa gmail.com> writes:

On Sunday, 30 December 2012 at 12:51:58 UTC, bearophile wrote:
 Omid:

 arr = [[1,2,3,4,5,6],[7,8,9,10,11,12],[13,14,15,16,17,18]]

 I want to obtain a subarray like

 assert(arr[][0] == [1,7,13]);

 This gives a range, not an array, so if you want an array, you 
 have to call std.array.array later:

 http://dlang.org/phobos/std_range.html#transversal


 assert(arr[1][] == [7,8,9,10,11,12];

 Just use array[1]. Or array[1].dup is you want a copy.


 assert(arr[0,2][1] == [2,14]);

 Enumerated indexes are not supported, so you need a iota + 
 filter + transversal + array.


 assert(arr[0,2][0..3,5] == [[1,2,3,6],[13,14,15,18]]);

 This requires a iota + filter + chain + array, or something 
 like that.

 If you don't want to do all this, you have to write your 
 slicing and dicing array struct :-( Someday it will probably be 
 present in Phobos.

 Bye,
 bearophile

Thanks, though I didn't understand a word you said:). I should 
learn iota, filter, transversal first.

"bearophile" <bearophileHUGS lycos.com> writes:

Omid:

 Thanks, though I didn't understand a word you said:).

This code works with the latest beta compiler:


import std.algorithm: filter, equal, map, canFind;
import std.range: transversal, iota;

void main() {
     auto arr = [[ 1, 2, 3, 4, 5, 6],
                 [ 7, 8, 9,10,11,12],
                 [13,14,15,16,17,18]];

     auto r1 = transversal(arr, 0);
     assert(r1.equal([1, 7, 13]));

     assert(arr[1] == [7,8,9,10,11,12]);

     auto r2 = [0, 2]
               .map!(i => arr[i])()
               .transversal(1);
     assert(r2.equal([2, 14]));

     auto r3 = [0, 2]
               .map!(i => arr[i][0..3] ~ arr[i][5])();
     assert(r3.equal([[1,2,3,6],[13,14,15,18]]));
}


Bye,
bearophile

"Omid" <mehdioa gmail.com> writes:

On Sunday, 30 December 2012 at 18:55:50 UTC, bearophile wrote:
 Omid:


 This code works with the latest beta compiler:


 import std.algorithm: filter, equal, map, canFind;
 import std.range: transversal, iota;

 void main() {
     auto arr = [[ 1, 2, 3, 4, 5, 6],
                 [ 7, 8, 9,10,11,12],
                 [13,14,15,16,17,18]];

     auto r1 = transversal(arr, 0);
     assert(r1.equal([1, 7, 13]));

     assert(arr[1] == [7,8,9,10,11,12]);

     auto r2 = [0, 2]
               .map!(i => arr[i])()
               .transversal(1);
     assert(r2.equal([2, 14]));

     auto r3 = [0, 2]
               .map!(i => arr[i][0..3] ~ arr[i][5])();
     assert(r3.equal([[1,2,3,6],[13,14,15,18]]));
 }


 Bye,
 bearophile

Thanks again. I started learning std.array and I should say it 
fits all my needs as a mathematics and combinatorics researcher. 
Now I think I am able to give up commercial softwares.

"Omid" <mehdioa gmail.com> writes:

On Monday, 31 December 2012 at 13:29:02 UTC, Omid wrote:

I started learning std.array

Actually, std.array and std.range both.