chooseAmong

1 auto test()
2 {
3     import std.algorithm.comparison : equal;
4 
5     int[4] sarr1 = [1, 2, 3, 4];
6     int[2] sarr2 = [5, 6];
7     int[1] sarr3 = [7];
8     auto arr1 = sarr1[];
9     auto arr2 = sarr2[];
10     auto arr3 = sarr3[];
11 
12     {
13         auto s = chooseAmong(0, arr1, arr2, arr3);
14         auto t = s.save;
15         assert(s.length == 4);
16         assert(s[2] == 3);
17         s.popFront();
18         assert(equal(t, only(1, 2, 3, 4)));
19     }
20     {
21         auto s = chooseAmong(1, arr1, arr2, arr3);
22         assert(s.length == 2);
23         s.front = 8;
24         assert(equal(s, only(8, 6)));
25     }
26     {
27         auto s = chooseAmong(1, arr1, arr2, arr3);
28         assert(s.length == 2);
29         s[1] = 9;
30         assert(equal(s, only(8, 9)));
31     }
32     {
33         auto s = chooseAmong(1, arr2, arr1, arr3)[1 .. 3];
34         assert(s.length == 2);
35         assert(equal(s, only(2, 3)));
36     }
37     {
38         auto s = chooseAmong(0, arr1, arr2, arr3);
39         assert(s.length == 4);
40         assert(s.back == 4);
41         s.popBack();
42         s.back = 5;
43         assert(equal(s, only(1, 2, 5)));
44         s.back = 3;
45         assert(equal(s, only(1, 2, 3)));
46     }
47     {
48         uint[5] foo = [1, 2, 3, 4, 5];
49         uint[5] bar = [6, 7, 8, 9, 10];
50         auto c = chooseAmong(1, foo[], bar[]);
51         assert(c[3] == 9);
52         c[3] = 42;
53         assert(c[3] == 42);
54         assert(c.moveFront() == 6);
55         assert(c.moveBack() == 10);
56         assert(c.moveAt(4) == 10);
57     }
58     {
59         import std.range : cycle;
60         auto s = chooseAmong(0, cycle(arr2), cycle(arr3));
61         assert(isInfinite!(typeof(s)));
62         assert(!s.empty);
63         assert(s[100] == 8);
64         assert(s[101] == 9);
65         assert(s[0 .. 3].equal(only(8, 9, 8)));
66     }
67     return 0;
68 }
69 // works at runtime
70 auto a = test();
71 // and at compile time
72 static b = test();