Hello,

I have an array of objects of class C which contain a id member.
I want to figure out if all the id members are unique using functional primitives.

For example, if I have:

class C
{
  int id;
}

and an array of C 'Cs';

My idea was to do:

auto ids = Cs.map!(c => c.id);
assert(equal(ids.sort().uniq(), ids.sort()));

But it doesn't compile because I can't can call sort on ids.

Any idea why ? and how to solve my initial problem, which is to check all ids are unique.

Regards,

Dorian

On Wednesday, 31 August 2016 at 07:40:39 UTC, Dorian Haglund wrote:
> Hello,
>
> I have an array of objects of class C which contain a id member.
> I want to figure out if all the id members are unique using functional primitives.
>
> For example, if I have:
>
> class C
> {
>   int id;
> }
>
> and an array of C 'Cs';
>
> My idea was to do:
>
> auto ids = Cs.map!(c => c.id);
> assert(equal(ids.sort().uniq(), ids.sort()));
>
> But it doesn't compile because I can't can call sort on ids.
>
> Any idea why ? and how to solve my initial problem, which is to check all ids are unique.
>
> Regards,
>
> Dorian

Sort require an indexable array. You can convert an insertRange to an indexable array with .array:
ids.array.sort()

You can also directly sort on id
Cs.array.sort!((a,b) => a.id < b.id);

On Wednesday, 31 August 2016 at 07:40:39 UTC, Dorian Haglund wrote:
> Hello,
>
> I have an array of objects of class C which contain a id member.
> I want to figure out if all the id members are unique using functional primitives.
>
> For example, if I have:
>
> class C
> {
>   int id;
> }
>
> and an array of C 'Cs';
>
> My idea was to do:
>
> auto ids = Cs.map!(c => c.id);
> assert(equal(ids.sort().uniq(), ids.sort()));
>
> But it doesn't compile because I can't can call sort on ids.
>
> Any idea why ? and how to solve my initial problem, which is to check all ids are unique.
>
> Regards,
>
> Dorian

Something like this: https://dpaste.dzfl.pl/9fa55b2a7927 ?

Andrea

@Edwin: Thank you for the insight about indexed range.

@Adrea: Thanks, this looks good. Even if I found it a little obscure at first sight, it's better than my previous solution.

On Wednesday, 31 August 2016 at 08:38:11 UTC, Andrea Fontana wrote:
> Something like this: https://dpaste.dzfl.pl/9fa55b2a7927 ?
>
> Andrea

Or use findAdjacent:

auto idsAreUnique = ids.array.sort.findAdjacent.empty;

http://dlang.org/phobos/std_algorithm_searching.html#.findAdjacent

On Wednesday, 31 August 2016 at 07:40:39 UTC, Dorian Haglund wrote:
> Hello,
>
> I have an array of objects of class C which contain a id member.
> I want to figure out if all the id members are unique using functional primitives.
>
> For example, if I have:
>
> class C
> {
>   int id;
> }
>
> and an array of C 'Cs';
>
> My idea was to do:
>
> auto ids = Cs.map!(c => c.id);
> assert(equal(ids.sort().uniq(), ids.sort()));
>
> But it doesn't compile because I can't can call sort on ids.
>
> Any idea why ? and how to solve my initial problem, which is to check all ids are unique.
>
> Regards,
>
> Dorian


Your post inspired me to write this addition to my D library, I'll commit it later today but you can use it straightaway by just adding this file. It will be far more efficient than any of the other solutions posted here.

The file - http://pastebin.com/RN2nagEn
The library - https://github.com/pineapplemachine/mach.d

Example usage:

    import std.stdio;
    import mach.range.unique;
    class C{
        this(int id){this.id = id;}
        int id;
    }
    auto c0 = [new C(0), new C(1), new C(2), new C(3)];
    auto c1 = [new C(0), new C(1), new C(2), new C(3), new C(0)];
    c0.unique!(c => c.id).writeln; // true
    c1.unique!(c => c.id).writeln; // false