1//! # The Rust Prelude
2//!
3//! Rust comes with a variety of things in its standard library. However, if
4//! you had to manually import every single thing that you used, it would be
5//! very verbose. But importing a lot of things that a program never uses isn't
6//! good either. A balance needs to be struck.
7//!
8//! The *prelude* is the list of things that Rust automatically imports into
9//! every Rust program. It's kept as small as possible, and is focused on
10//! things, particularly traits, which are used in almost every single Rust
11//! program.
12//!
13//! # Other preludes
14//!
15//! Preludes can be seen as a pattern to make using multiple types more
16//! convenient. As such, you'll find other preludes in the standard library,
17//! such as [`std::io::prelude`]. Various libraries in the Rust ecosystem may
18//! also define their own preludes.
19//!
20//! [`std::io::prelude`]: crate::io::prelude
21//!
22//! The difference between 'the prelude' and these other preludes is that they
23//! are not automatically `use`'d, and must be imported manually. This is still
24//! easier than importing all of their constituent components.
25//!
26//! # Prelude contents
27//!
28//! The first version of the prelude is used in Rust 2015 and Rust 2018,
29//! and lives in [`std::prelude::v1`].
30//! [`std::prelude::rust_2015`] and [`std::prelude::rust_2018`] re-export this prelude.
31//! It re-exports the following:
32//!
33//! * <code>[std::marker]::{[Copy], [Send], [Sized], [Sync], [Unpin]}</code>,
34//! marker traits that indicate fundamental properties of types.
35//! * <code>[std::ops]::{[Drop], [Fn], [FnMut], [FnOnce]}</code>, various
36//! operations for both destructors and overloading `()`.
37//! * <code>[std::mem]::[drop]</code>, a convenience function for explicitly
38//! dropping a value.
39//! * <code>[std::boxed]::[Box]</code>, a way to allocate values on the heap.
40//! * <code>[std::borrow]::[ToOwned]</code>, the conversion trait that defines
41//! [`to_owned`], the generic method for creating an owned type from a
42//! borrowed type.
43//! * <code>[std::clone]::[Clone]</code>, the ubiquitous trait that defines
44//! [`clone`][Clone::clone], the method for producing a copy of a value.
45//! * <code>[std::cmp]::{[PartialEq], [PartialOrd], [Eq], [Ord]}</code>, the
46//! comparison traits, which implement the comparison operators and are often
47//! seen in trait bounds.
48//! * <code>[std::convert]::{[AsRef], [AsMut], [Into], [From]}</code>, generic
49//! conversions, used by savvy API authors to create overloaded methods.
50//! * <code>[std::default]::[Default]</code>, types that have default values.
51//! * <code>[std::iter]::{[Iterator], [Extend], [IntoIterator], [DoubleEndedIterator], [ExactSizeIterator]}</code>,
52//! iterators of various
53//! kinds.
54//! * <code>[std::option]::[Option]::{[self][Option], [Some], [None]}</code>, a
55//! type which expresses the presence or absence of a value. This type is so
56//! commonly used, its variants are also exported.
57//! * <code>[std::result]::[Result]::{[self][Result], [Ok], [Err]}</code>, a type
58//! for functions that may succeed or fail. Like [`Option`], its variants are
59//! exported as well.
60//! * <code>[std::string]::{[String], [ToString]}</code>, heap-allocated strings.
61//! * <code>[std::vec]::[Vec]</code>, a growable, heap-allocated vector.
62//!
63//! The prelude used in Rust 2021, [`std::prelude::rust_2021`], includes all of the above,
64//! and in addition re-exports:
65//!
66//! * <code>[std::convert]::{[TryFrom], [TryInto]}</code>,
67//! * <code>[std::iter]::[FromIterator]</code>.
68//!
69//! [std::borrow]: crate::borrow
70//! [std::boxed]: crate::boxed
71//! [std::clone]: crate::clone
72//! [std::cmp]: crate::cmp
73//! [std::convert]: crate::convert
74//! [std::default]: crate::default
75//! [std::iter]: crate::iter
76//! [std::marker]: crate::marker
77//! [std::mem]: crate::mem
78//! [std::ops]: crate::ops
79//! [std::option]: crate::option
80//! [`std::prelude::v1`]: v1
81//! [`std::prelude::rust_2015`]: rust_2015
82//! [`std::prelude::rust_2018`]: rust_2018
83//! [`std::prelude::rust_2021`]: rust_2021
84//! [std::result]: crate::result
85//! [std::slice]: crate::slice
86//! [std::string]: crate::string
87//! [std::vec]: mod@crate::vec
88//! [`to_owned`]: crate::borrow::ToOwned::to_owned
89//! [book-closures]: ../../book/ch13-01-closures.html
90//! [book-dtor]: ../../book/ch15-03-drop.html
91//! [book-enums]: ../../book/ch06-01-defining-an-enum.html
92//! [book-iter]: ../../book/ch13-02-iterators.html
93
94#![stable(feature = "rust1", since = "1.0.0")]
95
96mod common;
97
98/// The first version of the prelude of The Rust Standard Library.
99///
100/// See the [module-level documentation](self) for more.
101#[stable(feature = "rust1", since = "1.0.0")]
102pub mod v1 {
103 #[stable(feature = "rust1", since = "1.0.0")]
104 pub use super::common::*;
105
106 // Do not `doc(inline)` these `doc(hidden)` items.
107 #[unstable(
108 feature = "rustc_encodable_decodable",
109 issue = "none",
110 soft,
111 reason = "derive macro for `rustc-serialize`; should not be used in new code"
112 )]
113 #[allow(deprecated)]
114 pub use core::prelude::v1::{RustcDecodable, RustcEncodable};
115}
116
117/// The 2015 version of the prelude of The Rust Standard Library.
118///
119/// See the [module-level documentation](self) for more.
120#[stable(feature = "prelude_2015", since = "1.55.0")]
121pub mod rust_2015 {
122 #[stable(feature = "prelude_2015", since = "1.55.0")]
123 #[doc(no_inline)]
124 pub use super::v1::*;
125}
126
127/// The 2018 version of the prelude of The Rust Standard Library.
128///
129/// See the [module-level documentation](self) for more.
130#[stable(feature = "prelude_2018", since = "1.55.0")]
131pub mod rust_2018 {
132 #[stable(feature = "prelude_2018", since = "1.55.0")]
133 #[doc(no_inline)]
134 pub use super::v1::*;
135}
136
137/// The 2021 version of the prelude of The Rust Standard Library.
138///
139/// See the [module-level documentation](self) for more.
140#[stable(feature = "prelude_2021", since = "1.55.0")]
141pub mod rust_2021 {
142 #[stable(feature = "prelude_2021", since = "1.55.0")]
143 #[doc(no_inline)]
144 pub use super::v1::*;
145
146 #[stable(feature = "prelude_2021", since = "1.55.0")]
147 #[doc(no_inline)]
148 pub use core::prelude::rust_2021::*;
149}
150
151/// The 2024 version of the prelude of The Rust Standard Library.
152///
153/// See the [module-level documentation](self) for more.
154#[unstable(feature = "prelude_2024", issue = "121042")]
155pub mod rust_2024 {
156 #[stable(feature = "rust1", since = "1.0.0")]
157 pub use super::common::*;
158
159 #[unstable(feature = "prelude_2024", issue = "121042")]
160 #[doc(no_inline)]
161 pub use core::prelude::rust_2024::*;
162}
163