1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
// Copyright (c) 2025-2026 Zensical and contributors
// SPDX-License-Identifier: MIT
// All contributions are certified under the DCO
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
// sell copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
// IN THE SOFTWARE.
// ----------------------------------------------------------------------------
//! Identifier.
use ;
use Hash;
// ----------------------------------------------------------------------------
// Traits
// ----------------------------------------------------------------------------
/// Identifier.
///
/// This trait defines the requirements for identifiers, which are the central
/// means of identifying inputs and outputs of actions. Note that identifiers
/// will mostly be encountered in the context of a [`Scope`], which allows for
/// modelling the hierarchical structure of computations.
///
/// Identifiers are required to implement [`Eq`], [`Hash`] and [`Ord`], so they
/// can be stored for stateful operators, whereas [`Display`] and [`Debug`] are
/// required for tracing and debugging purposes. Of course, identifiers must be
/// [`Send`] and [`Sync`] to be usable in worker threads. Types which implement
/// all of those traits can be used as identifiers in the scheduler, because we
/// provide a blanket implementation of this trait.
///
/// We assume that identifiers are cheap to clone, so the use of [`Arc`][] is
/// strongly recommended when using string-based identifiers.
///
/// __Warning__: The `'static` lifetime which is required by this trait is a
/// deliberate design choice to simplify passing data to threads. If we would
/// not require the lifetime, we would need to add a lifetime parameter to all
/// types consuming this trait, which is cumbersome to use.
///
/// [`Arc`]: std::sync::Arc
// ----------------------------------------------------------------------------
// Blanket implementations
// ----------------------------------------------------------------------------