nxt.container.common source code

1 /** Helpers used by containers.
2  */
3 module nxt.container.common;
4 
5 /** Try to pop first occurrence of `needle` in `haystack` (if any).
6     Returns: `true` iff pop was made, `false` otherwise.
7  */
8 bool popFirstMaybe(alias pred = "a == b", C, E)(ref C haystack, in E needle)
9 if (__traits(hasMember, C, "length") &&
10     __traits(hasMember, C, "popAt"))
11     // TODO: activate this restriction
12     // if (hasSlicing!C &&
13     //     is(ElementType!C == E.init))
14 {
15     import std.functional : binaryFun;
16     // doesn't work for uncopyable element types: import std.algorithm.searching : countUntil;
17     size_t offset = 0;
18     foreach (const ref e; haystack[])
19     {
20         if (binaryFun!pred(e, needle))
21             break;
22         offset += 1;
23     }
24     if (offset != haystack.length)
25     {
26         haystack.popAt(offset);
27         return true;
28     }
29     return false;
30 }
31 
32 /** Remove element at index `index` in `r`.
33  *
34  * TODO: reuse in array*.d
35  * TODO: better name removeAt
36  */
37 void shiftToFrontAt(T)(T[] r, size_t index) @trusted
38 {
39     assert(index + 1 <= r.length);
40 
41     // TODO: use this instead:
42     // immutable si = index + 1;   // source index
43     // immutable ti = index;       // target index
44     // immutable restLength = this.length - (index + 1);
45     // moveEmplaceAll(_store.ptr[si .. si + restLength],
46     //                _store.ptr[ti .. ti + restLength]);
47 
48     // for each element index that needs to be moved
49     foreach (immutable i; 0 .. r.length - (index + 1))
50     {
51         immutable si = index + i + 1; // source index
52         immutable ti = index + i;     // target index
53         import core.lifetime : moveEmplace;
54         moveEmplace(r.ptr[si], // TODO: remove `move` when compiler does it for us
55                     r.ptr[ti]);
56     }
57 }
58 
59 @safe pure nothrow @nogc unittest
60 {
61     int[4] x = [11, 12, 13, 14];
62     x[].shiftToFrontAt(1);
63     assert(x == [11, 13, 14, 14]);
64 }