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digitalmars.D.learn - Checking all elements are unique.

reply Dorian Haglund <dorian.haglund gmail.com> writes:
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
Aug 31 2016
next sibling parent Edwin van Leeuwen <edder tkwsping.nl> writes:
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);
Aug 31 2016
prev sibling next sibling parent reply Andrea Fontana <nospam example.com> writes:
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
Aug 31 2016
next sibling parent Dorian Haglund <dorian.haglund gmail.com> writes:
 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.
Aug 31 2016
prev sibling parent Rene Zwanenburg <renezwanenburg gmail.com> writes:
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;
Aug 31 2016
prev sibling parent pineapple <meapineapple gmail.com> writes:
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
Aug 31 2016