newbie question: Can D do this?

[Ali Çehreli]

On 12/19/2011 08:17 AM, clk wrote:

 > I'm a little bit intimidated by the fact that the topics in the d-learn
 > list look rather advanced to a newbie like me.

We need more newbie topics here! :)

 > 1) Does D support something like the javascript 1.8 destructuring
 > assigment (multiple assigment in python):
 >
 > [a, b] = [b, a];

No multiple assignment like that. But useful approarches exist for most 
needs, like the swap that simendsjo has shown.

 > 2) D doesn't seem to support the list comprehension syntax available in
 > python and javascript. Is this correct?
 >
 > [f(x) for x in list if condition]

List comprehension is not part of the language.

import std.algorithm;

void f(int x)
{}

bool condition(int x)
{
     return true;
}

void main()
{
     auto list = [ 0, 1, 2 ];
     map!f(filter!condition(list));
}

You can define f and condition within the body of main().

It is possible to use function literals as well:

import std.algorithm;

void main()
{
     auto list = [ 0, 1, 2 ];
     map!((x){
             /* ... this is f(x) ...*/
         })(filter!((x) {
                     return true; /* ... condition ... */
                 })(list));
}

 > 3) D's slice operator apparently doesn't allow the use of a stride other
 > than unity as is allowed with fortran and matlab. Is there a way to
 > implement this feature so that
 >
 > [1, 2, 3, 4, 5][0..$:2] would refer to [1, 3, 5], etc..., where 2 is the
 > non unit stride. Or is the find function from std.algorithm the only
 > option to achieve the same behavior.

std.range.stride does that:

import std.range;
// ...
stride([1, 2, 3, 4, 5], 2)

 >
 > I find the 3 features above extremely convenient in every day coding.
 > Thanks,
 > -clk
 >
 >

Ali