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Rollup merge of rust-lang#29785 - steveklabnik:doc_prelude, r=nikomat…
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…sakis

This mostly brings them in line with existing linking convention, but
also has some minor re-wording.

The text at the top has been re-focused, by starting out with what the
prelude does, rather than starting from injecting std.

Also, it now mentions that other preludes exist.

Part of rust-lang#29369
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@Manishearth
Manishearth committed Nov 12, 2015
2 parents b7f6d72 + a1b2476 commit 5b55b8d
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209 changes: 113 additions & 96 deletions src/libstd/prelude/mod.rs
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//! The Rust Prelude
//!
//! Because `std` is required by most serious Rust software, it is
//! imported at the topmost level of every crate by default, as if
//! each crate contains the following:
//! 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, particuarly traits, which are used in almost every single Rust
//! program.
//!
//! On a technical level, Rust inserts
//!
//! ```ignore
//! extern crate std;
//! ```
//!
//! This means that the contents of std can be accessed from any context
//! with the `std::` path prefix, as in `use std::vec`, `use std::thread::spawn`,
//! etc.
//!
//! Additionally, `std` contains a versioned *prelude* that reexports many of the
//! most common traits, types, and functions. *The contents of the prelude are
//! imported into every module by default*. Implicitly, all modules behave as if
//! they contained the following [`use` statement][book-use]:
//!
//! [book-use]: ../../book/crates-and-modules.html#importing-modules-with-use
//! into the crate root of every crate, and
//!
//! ```ignore
//! use std::prelude::v1::*;
//! ```
//!
//! The prelude is primarily concerned with exporting *traits* that
//! are so pervasive that they would be onerous to import for every use,
//! particularly those that are commonly mentioned in [generic type
//! bounds][book-traits].
//! into every module.
//!
//! # 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`]: ../io/prelude/index.html
//!
//! The differece 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 consitutent components.
//!
//! # Prelude contents
//!
//! The current version of the prelude (version 1) lives in
//! [`std::prelude::v1`](v1/index.html), and reexports the following.
//! [`std::prelude::v1`], and reexports the following.
//!
//! * `std::marker::`{
//! [`Copy`](../marker/trait.Copy.html),
//! [`Send`](../marker/trait.Send.html),
//! [`Sized`](../marker/trait.Sized.html),
//! [`Sync`](../marker/trait.Sync.html)
//! }.
//! The marker traits indicate fundamental properties of types.
//! * `std::ops::`{
//! [`Drop`](../ops/trait.Drop.html),
//! [`Fn`](../ops/trait.Fn.html),
//! [`FnMut`](../ops/trait.FnMut.html),
//! [`FnOnce`](../ops/trait.FnOnce.html)
//! }.
//! The [destructor][book-dtor] trait and the
//! [closure][book-closures] traits, reexported from the same
//! [module that also defines overloaded
//! operators](../ops/index.html).
//! * `std::mem::`[`drop`](../mem/fn.drop.html).
//! A convenience function for explicitly dropping a value.
//! * `std::boxed::`[`Box`](../boxed/struct.Box.html).
//! The owned heap pointer.
//! * `std::borrow::`[`ToOwned`](../borrow/trait.ToOwned.html).
//! The conversion trait that defines `to_owned`, the generic method
//! for creating an owned type from a borrowed type.
//! * `std::clone::`[`Clone`](../clone/trait.Clone.html).
//! The ubiquitous trait that defines `clone`, the method for
//! producing copies of values that are consider expensive to copy.
//! * `std::cmp::`{
//! [`PartialEq`](../cmp/trait.PartialEq.html),
//! [`PartialOrd`](../cmp/trait.PartialOrd.html),
//! [`Eq`](../cmp/trait.Eq.html),
//! [`Ord`](../cmp/trait.Ord.html)
//! }.
//! The comparison traits, which implement the comparison operators
//! and are often seen in trait bounds.
//! * `std::convert::`{
//! [`AsRef`](../convert/trait.AsRef.html),
//! [`AsMut`](../convert/trait.AsMut.html),
//! [`Into`](../convert/trait.Into.html),
//! [`From`](../convert/trait.From.html)
//! }.
//! Generic conversions, used by savvy API authors to create
//! overloaded methods.
//! * `std::default::`[`Default`](../default/trait.Default.html).
//! Types that have default values.
//! * `std::iter::`{
//! [`Iterator`](../iter/trait.Iterator.html),
//! [`Extend`](../iter/trait.Extend.html),
//! [`IntoIterator`](../iter/trait.IntoIterator.html),
//! [`DoubleEndedIterator`](../iter/trait.DoubleEndedIterator.html),
//! [`ExactSizeIterator`](../iter/trait.ExactSizeIterator.html)
//! }.
//! [Iterators][book-iter].
//! * `std::option::Option::`{
//! [`self`](../option/enum.Option.html),
//! [`Some`](../option/enum.Option.html),
//! [`None`](../option/enum.Option.html)
//! }.
//! The ubiquitous `Option` type and its two [variants][book-enums],
//! `Some` and `None`.
//! * `std::result::Result::`{
//! [`self`](../result/enum.Result.html),
//! [`Ok`](../result/enum.Result.html),
//! [`Err`](../result/enum.Result.html)
//! }.
//! The ubiquitous `Result` type and its two [variants][book-enums],
//! `Ok` and `Err`.
//! * `std::slice::`[`SliceConcatExt`](../slice/trait.SliceConcatExt.html).
//! An unstable extension to slices that shouldn't have to exist.
//! * `std::string::`{
//! [`String`](../string/struct.String.html),
//! [`ToString`](../string/trait.ToString.html)
//! }.
//! Heap allocated strings.
//! * `std::vec::`[`Vec`](../vec/struct.Vec.html).
//! Heap allocated vectors.
//! * [`std::marker`]::{[`Copy`], [`Send`], [`Sized`], [`Sync`]}. The marker
//! traits indicate fundamental properties of types.
//! * [`std::ops`]::{[`Drop`], [`Fn`], [`FnMut`], [`FnOnce`]}. Various
//! operations for both destuctors and overloading `()`.
//! * [`std::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()`],
//! 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`, `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`, `Ok`, `Err`}. A type for functions
//! that may succeed or fail. Like [`Option`], its variants are exported as
//! well.
//! * [`std::slice`]::[`SliceConcatExt`], a trait that exists for technical
//! reasons, but shouldn't have to exist. It provides a few useful methods on
//! slices.
//! * [`std::string`]::{[`String`], [`ToString`]}, heap allocated strings.
//! * [`std::vec`]::[`Vec`](../vec/struct.Vec.html), a growable, heap-allocated
//! vector.
//!
//! [book-traits]: ../../book/traits.html
//! [`AsMut`]: ../convert/trait.AsMut.html
//! [`AsRef`]: ../convert/trait.AsRef.html
//! [`Box`]: ../boxed/struct.Box.html
//! [`Clone`]: ../clone/trait.Clone.html
//! [`Copy`]: ../marker/trait.Copy.html
//! [`Default`]: ../default/trait.Default.html
//! [`DoubleEndedIterator`]: ../iter/trait.DoubleEndedIterator.html
//! [`Drop`]: ../ops/trait.Drop.html
//! [`Eq`]: ../cmp/trait.Eq.html
//! [`ExactSizeIterator`]: ../iter/trait.ExactSizeIterator.html
//! [`Extend`]: ../iter/trait.Extend.html
//! [`FnMut`]: ../ops/trait.FnMut.html
//! [`FnOnce`]: ../ops/trait.FnOnce.html
//! [`Fn`]: ../ops/trait.Fn.html
//! [`From`]: ../convert/trait.From.html
//! [`IntoIterator`]: ../iter/trait.IntoIterator.html
//! [`Into`]: ../convert/trait.Into.html
//! [`Iterator`]: ../iter/trait.Iterator.html
//! [`Option`]: ../option/enum.Option.html
//! [`Ord`]: ../cmp/trait.Ord.html
//! [`PartialEq`]: ../cmp/trait.PartialEq.html
//! [`PartialOrd`]: ../cmp/trait.PartialOrd.html
//! [`Result`]: ../result/enum.Result.html
//! [`Send`]: ../marker/trait.Send.html
//! [`Sized`]: ../marker/trait.Sized.html
//! [`SliceConcatExt`]: ../slice/trait.SliceConcatExt.html
//! [`String`]: ../string/struct.String.html
//! [`Sync`]: ../marker/trait.Sync.html
//! [`ToOwned`]: ../borrow/trait.ToOwned.html
//! [`ToString`]: ../string/trait.ToString.html
//! [`Vec`]: ../vec/struct.Vec.html
//! [`clone()`]: ../clone/trait.Clone.html#tymethod.clone
//! [`drop`]: ../mem/fn.drop.html
//! [`std::borrow`]: ../borrow/index.html
//! [`std::boxed`]: ../boxed/index.html
//! [`std::clone`]: ../clone/index.html
//! [`std::cmp`]: ../cmp/index.html
//! [`std::convert`]: ../convert/index.html
//! [`std::default`]: ../default/index.html
//! [`std::iter`]: ../iter/index.html
//! [`std::marker`]: ../marker/index.html
//! [`std::mem`]: ../mem/index.html
//! [`std::ops`]: ../ops/index.html
//! [`std::option`]: ../option/index.html
//! [`std::prelude::v1`]: v1/index.html
//! [`std::result`]: ../result/index.html
//! [`std::slice`]: ../slice/index.html
//! [`std::string`]: ../string/index.html
//! [`std::vec`]: ../vec/index.html
//! [`to_owned()`]: ../borrow/trait.ToOwned.html#tymethod.to_owned
//! [book-closures]: ../../book/closures.html
//! [book-dtor]: ../../book/drop.html
//! [book-iter]: ../../book/iterators.html
//! [book-enums]: ../../book/enums.html
//! [book-iter]: ../../book/iterators.html
#![stable(feature = "rust1", since = "1.0.0")]

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2 changes: 2 additions & 0 deletions src/libstd/prelude/v1.rs
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// except according to those terms.

//! The first version of the prelude of The Rust Standard Library.
//!
//! See the [module-level documentation](../index.html) for more.
#![stable(feature = "rust1", since = "1.0.0")]

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