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//! # The Rust Prelude //! //! Rust comes with a variety of things in its standard library. However, if //! you had to manually import every single thing that you used, it would be //! very verbose. But importing a lot of things that a program never uses isn't //! good either. A balance needs to be struck. //! //! The *prelude* is the list of things that Rust automatically imports into //! every Rust program. It's kept as small as possible, and is focused on //! things, particularly traits, which are used in almost every single Rust //! program. //! //! # Other preludes //! //! Preludes can be seen as a pattern to make using multiple types more //! convenient. As such, you'll find other preludes in the standard library, //! such as [`std::io::prelude`]. Various libraries in the Rust ecosystem may //! also define their own preludes. //! //! [`std::io::prelude`]: crate::io::prelude //! //! The difference between 'the prelude' and these other preludes is that they //! are not automatically `use`'d, and must be imported manually. This is still //! easier than importing all of their constituent components. //! //! # Prelude contents //! //! The current version of the prelude (version 1) lives in //! [`std::prelude::v1`], and re-exports the following: //! //! * [`std::marker`]::{[`Copy`], [`Send`], [`Sized`], [`Sync`], [`Unpin`]}: //! marker traits that indicate fundamental properties of types. //! * [`std::ops`]::{[`Drop`], [`Fn`], [`FnMut`], [`FnOnce`]}: various //! operations for both destructors and overloading `()`. //! * [`std::mem`]::[`drop`][`mem::drop`]: a convenience function for explicitly //! dropping a value. //! * [`std::boxed`]::[`Box`]: a way to allocate values on the heap. //! * [`std::borrow`]::[`ToOwned`]: the conversion trait that defines //! [`to_owned`], the generic method for creating an owned type from a //! borrowed type. //! * [`std::clone`]::[`Clone`]: the ubiquitous trait that defines //! [`clone`][`Clone::clone`], the method for producing a copy of a value. //! * [`std::cmp`]::{[`PartialEq`], [`PartialOrd`], [`Eq`], [`Ord`]}: the //! comparison traits, which implement the comparison operators and are often //! seen in trait bounds. //! * [`std::convert`]::{[`AsRef`], [`AsMut`], [`Into`], [`From`]}: generic //! conversions, used by savvy API authors to create overloaded methods. //! * [`std::default`]::[`Default`], types that have default values. //! * [`std::iter`]::{[`Iterator`], [`Extend`], [`IntoIterator`], //! [`DoubleEndedIterator`], [`ExactSizeIterator`]}: iterators of various //! kinds. //! * [`std::option`]::[`Option`]::{[`self`][`Option`], [`Some`], [`None`]}, a //! type which expresses the presence or absence of a value. This type is so //! commonly used, its variants are also exported. //! * [`std::result`]::[`Result`]::{[`self`][`Result`], [`Ok`], [`Err`]}: a type //! for functions that may succeed or fail. Like [`Option`], its variants are //! exported as well. //! * [`std::string`]::{[`String`], [`ToString`]}: heap-allocated strings. //! * [`std::vec`]::[`Vec`]: a growable, heap-allocated vector. //! //! [`mem::drop`]: crate::mem::drop //! [`std::borrow`]: crate::borrow //! [`std::boxed`]: crate::boxed //! [`std::clone`]: crate::clone //! [`std::cmp`]: crate::cmp //! [`std::convert`]: crate::convert //! [`std::default`]: crate::default //! [`std::iter`]: crate::iter //! [`std::marker`]: crate::marker //! [`std::mem`]: crate::mem //! [`std::ops`]: crate::ops //! [`std::option`]: crate::option //! [`std::prelude::v1`]: v1 //! [`std::result`]: crate::result //! [`std::slice`]: crate::slice //! [`std::string`]: crate::string //! [`std::vec`]: mod@crate::vec //! [`to_owned`]: crate::borrow::ToOwned::to_owned //! [book-closures]: ../../book/ch13-01-closures.html //! [book-dtor]: ../../book/ch15-03-drop.html //! [book-enums]: ../../book/ch06-01-defining-an-enum.html //! [book-iter]: ../../book/ch13-02-iterators.html #![stable(feature = "rust1", since = "1.0.0")] pub mod v1; /// The 2015 version of the prelude of The Rust Standard Library. /// /// See the [module-level documentation](self) for more. #[unstable(feature = "prelude_2015", issue = "none")] pub mod rust_2015 { #[unstable(feature = "prelude_2015", issue = "none")] #[doc(no_inline)] pub use super::v1::*; } /// The 2018 version of the prelude of The Rust Standard Library. /// /// See the [module-level documentation](self) for more. #[unstable(feature = "prelude_2018", issue = "none")] pub mod rust_2018 { #[unstable(feature = "prelude_2018", issue = "none")] #[doc(no_inline)] pub use super::v1::*; } /// The 2021 version of the prelude of The Rust Standard Library. /// /// See the [module-level documentation](self) for more. #[unstable(feature = "prelude_2021", issue = "none")] pub mod rust_2021 { #[unstable(feature = "prelude_2021", issue = "none")] #[doc(no_inline)] pub use super::v1::*; #[unstable(feature = "prelude_2021", issue = "none")] #[doc(no_inline)] pub use core::prelude::rust_2021::*; }