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Programming in D: The Ultimate Guide for Software Engineers

Slices: Termination of Sharing

In this lesson, we will discuss the concept of termination of sharing in slices.

We'll cover the following...

Slice sharing #

It is possible to access the same elements by more than one slice. For example, the first two of the eight elements below are being accessed through three slices:

D
import std.stdio;
void main() {
    int[] slice = [ 1, 3, 5, 7, 9, 11, 13, 15 ];
    int[] half = slice[0 .. $ / 2];
    int[] quarter = slice[0 .. $ / 4];
    quarter[1] = 0;     // modify through one slice
    writeln(quarter);
    writeln(half);
    writeln(slice);
}

The effect of the modification to the second element of quarter is seen through all slices.

Making a slice longer may terminate sharing #

When viewed this way, slices provide shared access to elements. This sharing poses the question of what happens when a new element is added to one of the slices. Since multiple slices can provide access to the same elements, there may not be room to add elements to a slice without stomping on the elements of other slices of the same array.

D disallows element stomping and answers this question by terminating the sharing relationship if there is no room for the new ...