proper range usage

[Alex via Digitalmars-d-learn]

On Tuesday, 3 November 2015 at 08:23:20 UTC, Ali Çehreli wrote:
> > "Programming in D" book (the revision of 2015-10-24)
>
> Oooh! That smells very fresh. :)
>
:)

> > In my case, the container class can't become empty. Even if
> it contains
> > one single element, in this case the example should return
> true for
> > begin == end, it is not empty.
>
> That problem is solved by the convention that 'end' is one 
> beyond the last valid element. So, when there is only the 
> element 42, then begin==42 and end==43. Only when the last 
> element (42 in this case) is consumed, begin==end.
>
This part is dangerous, and I'm not sure how dangerous it is. 
Now, I have to dive into my structure a little bit deeper:
Say, I have three classes:


class B //current structure
{
     M[] _ms;
     P[] _ps;
     P[M] assoc;
}

struct M
{
     int id;
     alias id this;
}

struct P
{
     int id;
     alias id this;
     int begin;
     int end;
}

The idea is, that P structs are disjunct (and contigous, if this 
does matter) arrays of M's. And the question is, what happens, if 
I set the end property of a P to a number, which belongs to 
another P.
At the current time class B contains arrays of different M's 
(constant, big one, say order of 10^6 elements, elements itself 
are not very large, say about 5 members and a bunch of properties 
calculated at runtime) as well as an array of P's (at the 
beginning not so big one, but growing fast) and the array of 
associations between the M's and P's. In my program I implement 
this array as int[int], and reassign the associated values at the 
same time as the array of P's is growing.

Here I have to deliver the "buzz words", so I'm trying to 
implement a set partition algorithm with disjoint sets. With the 
standard question how to achieve the fastest cutting of the whole 
array into its single components. The application in my case are 
just some constraints which say, how the cutting is allowed.

> Such ranges are called generators.
ok, cool! Thx.