Hi everybody!
I want create a multi array like python.
For example(in python):
a=[1,2]
a.append([1234],3)
a.append([[4],5],6)

and result is = [1,2,[1234],3,[[4],5],6]

How can I do this in D

On Saturday, 27 October 2012 at 21:16:56 UTC, xfiles wrote:
> Hi everybody!
> I want create a multi array like python.
> For example(in python):
> a=[1,2]
> a.append([1234],3)
> a.append([[4],5],6)
>
> and result is = [1,2,[1234],3,[[4],5],6]
>
> How can I do this in D

If you want to create it with one line, you can just write something like this:

int[] a = [1,2,[1234],3,[[4],5],6];

To build the array by appending to it, the ~= operator appends to an array in place:

int[] a = [1,2];
a ~= [[1234],3];
a ~= [[[4],5], 6];

You can also use the ~ operator:

a = [1,2,3];
a = a ~ [4, 5];
//a is now [1,2,3,4,5]

However, this is less efficient because it makes a copy of the original array.

The ~ and ~= operators can also append individual values:

a = [1];
a ~= 2;
a ~= 3;
//a is now [1,2,3]

Ack! I just realized that this doesn't work because D isn't dynamically typed. I've had way too much Ruby on the brain lately...

You could use std.variant to simulate dynamic typing, but can be a bit of a mess.
You also could do something like this:

int[][] a = [[1], [2, 3, 4], [5]];

That's also a bit ugly, though.
In the end, you'll probably end up structuring your data in some other way.

Next time I answer a question, I'd better make sure I'm thinking of the right language.

xfiles:

> I want create a multi array like python.
> For example(in python):
> a=[1,2]
> a.append([1234],3)
> a.append([[4],5],6)
>
> and result is = [1,2,[1234],3,[[4],5],6]
>
> How can I do this in D

In D there are several different ways to represent that data structure, but being D not dynamically typed (and not having algebraic data types) none of them are as nice as solutions in Python (or ML-derived languages).

This shows one way to do it in an efficient way:
http://rosettacode.org/wiki/Flatten_a_list#D

If efficiency is less important, you can use an heap-allocated multi-way tree. Or even a little hierarchy with two classes.

Another solution is to use some kind of variant/any/multi data type.

So explain your needs better and maybe someone will suggest what specif solution to use.

Bye,
bearophile