diff options
Diffstat (limited to 'library/std/src/primitive_docs.rs')
| -rw-r--r-- | library/std/src/primitive_docs.rs | 1110 |
1 files changed, 1110 insertions, 0 deletions
diff --git a/library/std/src/primitive_docs.rs b/library/std/src/primitive_docs.rs new file mode 100644 index 00000000000..86de509e80a --- /dev/null +++ b/library/std/src/primitive_docs.rs @@ -0,0 +1,1110 @@ +#[doc(primitive = "bool")] +#[doc(alias = "true")] +#[doc(alias = "false")] +// +/// The boolean type. +/// +/// The `bool` represents a value, which could only be either `true` or `false`. If you cast +/// a `bool` into an integer, `true` will be 1 and `false` will be 0. +/// +/// # Basic usage +/// +/// `bool` implements various traits, such as [`BitAnd`], [`BitOr`], [`Not`], etc., +/// which allow us to perform boolean operations using `&`, `|` and `!`. +/// +/// `if` always demands a `bool` value. [`assert!`], being an important macro in testing, +/// checks whether an expression returns `true`. +/// +/// ``` +/// let bool_val = true & false | false; +/// assert!(!bool_val); +/// ``` +/// +/// [`assert!`]: macro.assert.html +/// [`BitAnd`]: ops/trait.BitAnd.html +/// [`BitOr`]: ops/trait.BitOr.html +/// [`Not`]: ops/trait.Not.html +/// +/// # Examples +/// +/// A trivial example of the usage of `bool`, +/// +/// ``` +/// let praise_the_borrow_checker = true; +/// +/// // using the `if` conditional +/// if praise_the_borrow_checker { +/// println!("oh, yeah!"); +/// } else { +/// println!("what?!!"); +/// } +/// +/// // ... or, a match pattern +/// match praise_the_borrow_checker { +/// true => println!("keep praising!"), +/// false => println!("you should praise!"), +/// } +/// ``` +/// +/// Also, since `bool` implements the [`Copy`](marker/trait.Copy.html) trait, we don't +/// have to worry about the move semantics (just like the integer and float primitives). +/// +/// Now an example of `bool` cast to integer type: +/// +/// ``` +/// assert_eq!(true as i32, 1); +/// assert_eq!(false as i32, 0); +/// ``` +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_bool {} + +#[doc(primitive = "never")] +#[doc(alias = "!")] +// +/// The `!` type, also called "never". +/// +/// `!` represents the type of computations which never resolve to any value at all. For example, +/// the [`exit`] function `fn exit(code: i32) -> !` exits the process without ever returning, and +/// so returns `!`. +/// +/// `break`, `continue` and `return` expressions also have type `!`. For example we are allowed to +/// write: +/// +/// ``` +/// #![feature(never_type)] +/// # fn foo() -> u32 { +/// let x: ! = { +/// return 123 +/// }; +/// # } +/// ``` +/// +/// Although the `let` is pointless here, it illustrates the meaning of `!`. Since `x` is never +/// assigned a value (because `return` returns from the entire function), `x` can be given type +/// `!`. We could also replace `return 123` with a `panic!` or a never-ending `loop` and this code +/// would still be valid. +/// +/// A more realistic usage of `!` is in this code: +/// +/// ``` +/// # fn get_a_number() -> Option<u32> { None } +/// # loop { +/// let num: u32 = match get_a_number() { +/// Some(num) => num, +/// None => break, +/// }; +/// # } +/// ``` +/// +/// Both match arms must produce values of type [`u32`], but since `break` never produces a value +/// at all we know it can never produce a value which isn't a [`u32`]. This illustrates another +/// behaviour of the `!` type - expressions with type `!` will coerce into any other type. +/// +/// [`u32`]: primitive.str.html +/// [`exit`]: process/fn.exit.html +/// +/// # `!` and generics +/// +/// ## Infallible errors +/// +/// The main place you'll see `!` used explicitly is in generic code. Consider the [`FromStr`] +/// trait: +/// +/// ``` +/// trait FromStr: Sized { +/// type Err; +/// fn from_str(s: &str) -> Result<Self, Self::Err>; +/// } +/// ``` +/// +/// When implementing this trait for [`String`] we need to pick a type for [`Err`]. And since +/// converting a string into a string will never result in an error, the appropriate type is `!`. +/// (Currently the type actually used is an enum with no variants, though this is only because `!` +/// was added to Rust at a later date and it may change in the future.) With an [`Err`] type of +/// `!`, if we have to call [`String::from_str`] for some reason the result will be a +/// [`Result<String, !>`] which we can unpack like this: +/// +/// ```ignore (string-from-str-error-type-is-not-never-yet) +/// #[feature(exhaustive_patterns)] +/// // NOTE: this does not work today! +/// let Ok(s) = String::from_str("hello"); +/// ``` +/// +/// Since the [`Err`] variant contains a `!`, it can never occur. If the `exhaustive_patterns` +/// feature is present this means we can exhaustively match on [`Result<T, !>`] by just taking the +/// [`Ok`] variant. This illustrates another behaviour of `!` - it can be used to "delete" certain +/// enum variants from generic types like `Result`. +/// +/// ## Infinite loops +/// +/// While [`Result<T, !>`] is very useful for removing errors, `!` can also be used to remove +/// successes as well. If we think of [`Result<T, !>`] as "if this function returns, it has not +/// errored," we get a very intuitive idea of [`Result<!, E>`] as well: if the function returns, it +/// *has* errored. +/// +/// For example, consider the case of a simple web server, which can be simplified to: +/// +/// ```ignore (hypothetical-example) +/// loop { +/// let (client, request) = get_request().expect("disconnected"); +/// let response = request.process(); +/// response.send(client); +/// } +/// ``` +/// +/// Currently, this isn't ideal, because we simply panic whenever we fail to get a new connection. +/// Instead, we'd like to keep track of this error, like this: +/// +/// ```ignore (hypothetical-example) +/// loop { +/// match get_request() { +/// Err(err) => break err, +/// Ok((client, request)) => { +/// let response = request.process(); +/// response.send(client); +/// }, +/// } +/// } +/// ``` +/// +/// Now, when the server disconnects, we exit the loop with an error instead of panicking. While it +/// might be intuitive to simply return the error, we might want to wrap it in a [`Result<!, E>`] +/// instead: +/// +/// ```ignore (hypothetical-example) +/// fn server_loop() -> Result<!, ConnectionError> { +/// loop { +/// let (client, request) = get_request()?; +/// let response = request.process(); +/// response.send(client); +/// } +/// } +/// ``` +/// +/// Now, we can use `?` instead of `match`, and the return type makes a lot more sense: if the loop +/// ever stops, it means that an error occurred. We don't even have to wrap the loop in an `Ok` +/// because `!` coerces to `Result<!, ConnectionError>` automatically. +/// +/// [`String::from_str`]: str/trait.FromStr.html#tymethod.from_str +/// [`Result<String, !>`]: result/enum.Result.html +/// [`Result<T, !>`]: result/enum.Result.html +/// [`Result<!, E>`]: result/enum.Result.html +/// [`Ok`]: result/enum.Result.html#variant.Ok +/// [`String`]: string/struct.String.html +/// [`Err`]: result/enum.Result.html#variant.Err +/// [`FromStr`]: str/trait.FromStr.html +/// +/// # `!` and traits +/// +/// When writing your own traits, `!` should have an `impl` whenever there is an obvious `impl` +/// which doesn't `panic!`. As it turns out, most traits can have an `impl` for `!`. Take [`Debug`] +/// for example: +/// +/// ``` +/// #![feature(never_type)] +/// # use std::fmt; +/// # trait Debug { +/// # fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result; +/// # } +/// impl Debug for ! { +/// fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result { +/// *self +/// } +/// } +/// ``` +/// +/// Once again we're using `!`'s ability to coerce into any other type, in this case +/// [`fmt::Result`]. Since this method takes a `&!` as an argument we know that it can never be +/// called (because there is no value of type `!` for it to be called with). Writing `*self` +/// essentially tells the compiler "We know that this code can never be run, so just treat the +/// entire function body as having type [`fmt::Result`]". This pattern can be used a lot when +/// implementing traits for `!`. Generally, any trait which only has methods which take a `self` +/// parameter should have such an impl. +/// +/// On the other hand, one trait which would not be appropriate to implement is [`Default`]: +/// +/// ``` +/// trait Default { +/// fn default() -> Self; +/// } +/// ``` +/// +/// Since `!` has no values, it has no default value either. It's true that we could write an +/// `impl` for this which simply panics, but the same is true for any type (we could `impl +/// Default` for (eg.) [`File`] by just making [`default()`] panic.) +/// +/// [`fmt::Result`]: fmt/type.Result.html +/// [`File`]: fs/struct.File.html +/// [`Debug`]: fmt/trait.Debug.html +/// [`Default`]: default/trait.Default.html +/// [`default()`]: default/trait.Default.html#tymethod.default +/// +#[unstable(feature = "never_type", issue = "35121")] +mod prim_never {} + +#[doc(primitive = "char")] +// +/// A character type. +/// +/// The `char` type represents a single character. More specifically, since +/// 'character' isn't a well-defined concept in Unicode, `char` is a '[Unicode +/// scalar value]', which is similar to, but not the same as, a '[Unicode code +/// point]'. +/// +/// [Unicode scalar value]: http://www.unicode.org/glossary/#unicode_scalar_value +/// [Unicode code point]: http://www.unicode.org/glossary/#code_point +/// +/// This documentation describes a number of methods and trait implementations on the +/// `char` type. For technical reasons, there is additional, separate +/// documentation in [the `std::char` module](char/index.html) as well. +/// +/// # Representation +/// +/// `char` is always four bytes in size. This is a different representation than +/// a given character would have as part of a [`String`]. For example: +/// +/// ``` +/// let v = vec!['h', 'e', 'l', 'l', 'o']; +/// +/// // five elements times four bytes for each element +/// assert_eq!(20, v.len() * std::mem::size_of::<char>()); +/// +/// let s = String::from("hello"); +/// +/// // five elements times one byte per element +/// assert_eq!(5, s.len() * std::mem::size_of::<u8>()); +/// ``` +/// +/// [`String`]: string/struct.String.html +/// +/// As always, remember that a human intuition for 'character' may not map to +/// Unicode's definitions. For example, despite looking similar, the 'é' +/// character is one Unicode code point while 'é' is two Unicode code points: +/// +/// ``` +/// let mut chars = "é".chars(); +/// // U+00e9: 'latin small letter e with acute' +/// assert_eq!(Some('\u{00e9}'), chars.next()); +/// assert_eq!(None, chars.next()); +/// +/// let mut chars = "é".chars(); +/// // U+0065: 'latin small letter e' +/// assert_eq!(Some('\u{0065}'), chars.next()); +/// // U+0301: 'combining acute accent' +/// assert_eq!(Some('\u{0301}'), chars.next()); +/// assert_eq!(None, chars.next()); +/// ``` +/// +/// This means that the contents of the first string above _will_ fit into a +/// `char` while the contents of the second string _will not_. Trying to create +/// a `char` literal with the contents of the second string gives an error: +/// +/// ```text +/// error: character literal may only contain one codepoint: 'é' +/// let c = 'é'; +/// ^^^ +/// ``` +/// +/// Another implication of the 4-byte fixed size of a `char` is that +/// per-`char` processing can end up using a lot more memory: +/// +/// ``` +/// let s = String::from("love: ❤️"); +/// let v: Vec<char> = s.chars().collect(); +/// +/// assert_eq!(12, std::mem::size_of_val(&s[..])); +/// assert_eq!(32, std::mem::size_of_val(&v[..])); +/// ``` +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_char {} + +#[doc(primitive = "unit")] +// +/// The `()` type, also called "unit". +/// +/// The `()` type has exactly one value `()`, and is used when there +/// is no other meaningful value that could be returned. `()` is most +/// commonly seen implicitly: functions without a `-> ...` implicitly +/// have return type `()`, that is, these are equivalent: +/// +/// ```rust +/// fn long() -> () {} +/// +/// fn short() {} +/// ``` +/// +/// The semicolon `;` can be used to discard the result of an +/// expression at the end of a block, making the expression (and thus +/// the block) evaluate to `()`. For example, +/// +/// ```rust +/// fn returns_i64() -> i64 { +/// 1i64 +/// } +/// fn returns_unit() { +/// 1i64; +/// } +/// +/// let is_i64 = { +/// returns_i64() +/// }; +/// let is_unit = { +/// returns_i64(); +/// }; +/// ``` +/// +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_unit {} + +#[doc(primitive = "pointer")] +// +/// Raw, unsafe pointers, `*const T`, and `*mut T`. +/// +/// *[See also the `std::ptr` module](ptr/index.html).* +/// +/// Working with raw pointers in Rust is uncommon, typically limited to a few patterns. +/// Raw pointers can be unaligned or [`null`]. However, when a raw pointer is +/// dereferenced (using the `*` operator), it must be non-null and aligned. +/// +/// Storing through a raw pointer using `*ptr = data` calls `drop` on the old value, so +/// [`write`] must be used if the type has drop glue and memory is not already +/// initialized - otherwise `drop` would be called on the uninitialized memory. +/// +/// Use the [`null`] and [`null_mut`] functions to create null pointers, and the +/// [`is_null`] method of the `*const T` and `*mut T` types to check for null. +/// The `*const T` and `*mut T` types also define the [`offset`] method, for +/// pointer math. +/// +/// # Common ways to create raw pointers +/// +/// ## 1. Coerce a reference (`&T`) or mutable reference (`&mut T`). +/// +/// ``` +/// let my_num: i32 = 10; +/// let my_num_ptr: *const i32 = &my_num; +/// let mut my_speed: i32 = 88; +/// let my_speed_ptr: *mut i32 = &mut my_speed; +/// ``` +/// +/// To get a pointer to a boxed value, dereference the box: +/// +/// ``` +/// let my_num: Box<i32> = Box::new(10); +/// let my_num_ptr: *const i32 = &*my_num; +/// let mut my_speed: Box<i32> = Box::new(88); +/// let my_speed_ptr: *mut i32 = &mut *my_speed; +/// ``` +/// +/// This does not take ownership of the original allocation +/// and requires no resource management later, +/// but you must not use the pointer after its lifetime. +/// +/// ## 2. Consume a box (`Box<T>`). +/// +/// The [`into_raw`] function consumes a box and returns +/// the raw pointer. It doesn't destroy `T` or deallocate any memory. +/// +/// ``` +/// let my_speed: Box<i32> = Box::new(88); +/// let my_speed: *mut i32 = Box::into_raw(my_speed); +/// +/// // By taking ownership of the original `Box<T>` though +/// // we are obligated to put it together later to be destroyed. +/// unsafe { +/// drop(Box::from_raw(my_speed)); +/// } +/// ``` +/// +/// Note that here the call to [`drop`] is for clarity - it indicates +/// that we are done with the given value and it should be destroyed. +/// +/// ## 3. Get it from C. +/// +/// ``` +/// # #![feature(rustc_private)] +/// extern crate libc; +/// +/// use std::mem; +/// +/// unsafe { +/// let my_num: *mut i32 = libc::malloc(mem::size_of::<i32>()) as *mut i32; +/// if my_num.is_null() { +/// panic!("failed to allocate memory"); +/// } +/// libc::free(my_num as *mut libc::c_void); +/// } +/// ``` +/// +/// Usually you wouldn't literally use `malloc` and `free` from Rust, +/// but C APIs hand out a lot of pointers generally, so are a common source +/// of raw pointers in Rust. +/// +/// [`null`]: ../std/ptr/fn.null.html +/// [`null_mut`]: ../std/ptr/fn.null_mut.html +/// [`is_null`]: ../std/primitive.pointer.html#method.is_null +/// [`offset`]: ../std/primitive.pointer.html#method.offset +/// [`into_raw`]: ../std/boxed/struct.Box.html#method.into_raw +/// [`drop`]: ../std/mem/fn.drop.html +/// [`write`]: ../std/ptr/fn.write.html +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_pointer {} + +#[doc(primitive = "array")] +// +/// A fixed-size array, denoted `[T; N]`, for the element type, `T`, and the +/// non-negative compile-time constant size, `N`. +/// +/// There are two syntactic forms for creating an array: +/// +/// * A list with each element, i.e., `[x, y, z]`. +/// * A repeat expression `[x; N]`, which produces an array with `N` copies of `x`. +/// The type of `x` must be [`Copy`][copy]. +/// +/// Arrays of *any* size implement the following traits if the element type allows it: +/// +/// - [`Debug`][debug] +/// - [`IntoIterator`][intoiterator] (implemented for `&[T; N]` and `&mut [T; N]`) +/// - [`PartialEq`][partialeq], [`PartialOrd`][partialord], [`Eq`][eq], [`Ord`][ord] +/// - [`Hash`][hash] +/// - [`AsRef`][asref], [`AsMut`][asmut] +/// - [`Borrow`][borrow], [`BorrowMut`][borrowmut] +/// +/// Arrays of sizes from 0 to 32 (inclusive) implement [`Default`][default] trait +/// if the element type allows it. As a stopgap, trait implementations are +/// statically generated up to size 32. +/// +/// Arrays of *any* size are [`Copy`][copy] if the element type is [`Copy`][copy] +/// and [`Clone`][clone] if the element type is [`Clone`][clone]. This works +/// because [`Copy`][copy] and [`Clone`][clone] traits are specially known +/// to the compiler. +/// +/// Arrays coerce to [slices (`[T]`)][slice], so a slice method may be called on +/// an array. Indeed, this provides most of the API for working with arrays. +/// Slices have a dynamic size and do not coerce to arrays. +/// +/// You can move elements out of an array with a slice pattern. If you want +/// one element, see [`mem::replace`][replace]. +/// +/// # Examples +/// +/// ``` +/// let mut array: [i32; 3] = [0; 3]; +/// +/// array[1] = 1; +/// array[2] = 2; +/// +/// assert_eq!([1, 2], &array[1..]); +/// +/// // This loop prints: 0 1 2 +/// for x in &array { +/// print!("{} ", x); +/// } +/// ``` +/// +/// An array itself is not iterable: +/// +/// ```compile_fail,E0277 +/// let array: [i32; 3] = [0; 3]; +/// +/// for x in array { } +/// // error: the trait bound `[i32; 3]: std::iter::Iterator` is not satisfied +/// ``` +/// +/// The solution is to coerce the array to a slice by calling a slice method: +/// +/// ``` +/// # let array: [i32; 3] = [0; 3]; +/// for x in array.iter() { } +/// ``` +/// +/// You can also use the array reference's [`IntoIterator`] implementation: +/// +/// ``` +/// # let array: [i32; 3] = [0; 3]; +/// for x in &array { } +/// ``` +/// +/// You can use a slice pattern to move elements out of an array: +/// +/// ``` +/// fn move_away(_: String) { /* Do interesting things. */ } +/// +/// let [john, roa] = ["John".to_string(), "Roa".to_string()]; +/// move_away(john); +/// move_away(roa); +/// ``` +/// +/// [slice]: primitive.slice.html +/// [copy]: marker/trait.Copy.html +/// [clone]: clone/trait.Clone.html +/// [debug]: fmt/trait.Debug.html +/// [intoiterator]: iter/trait.IntoIterator.html +/// [partialeq]: cmp/trait.PartialEq.html +/// [partialord]: cmp/trait.PartialOrd.html +/// [eq]: cmp/trait.Eq.html +/// [ord]: cmp/trait.Ord.html +/// [hash]: hash/trait.Hash.html +/// [asref]: convert/trait.AsRef.html +/// [asmut]: convert/trait.AsMut.html +/// [borrow]: borrow/trait.Borrow.html +/// [borrowmut]: borrow/trait.BorrowMut.html +/// [default]: default/trait.Default.html +/// [replace]: mem/fn.replace.html +/// [`IntoIterator`]: iter/trait.IntoIterator.html +/// +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_array {} + +#[doc(primitive = "slice")] +#[doc(alias = "[")] +#[doc(alias = "]")] +#[doc(alias = "[]")] +/// A dynamically-sized view into a contiguous sequence, `[T]`. Contiguous here +/// means that elements are laid out so that every element is the same +/// distance from its neighbors. +/// +/// *[See also the `std::slice` module](slice/index.html).* +/// +/// Slices are a view into a block of memory represented as a pointer and a +/// length. +/// +/// ``` +/// // slicing a Vec +/// let vec = vec![1, 2, 3]; +/// let int_slice = &vec[..]; +/// // coercing an array to a slice +/// let str_slice: &[&str] = &["one", "two", "three"]; +/// ``` +/// +/// Slices are either mutable or shared. The shared slice type is `&[T]`, +/// while the mutable slice type is `&mut [T]`, where `T` represents the element +/// type. For example, you can mutate the block of memory that a mutable slice +/// points to: +/// +/// ``` +/// let mut x = [1, 2, 3]; +/// let x = &mut x[..]; // Take a full slice of `x`. +/// x[1] = 7; +/// assert_eq!(x, &[1, 7, 3]); +/// ``` +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_slice {} + +#[doc(primitive = "str")] +// +/// String slices. +/// +/// *[See also the `std::str` module](str/index.html).* +/// +/// The `str` type, also called a 'string slice', is the most primitive string +/// type. It is usually seen in its borrowed form, `&str`. It is also the type +/// of string literals, `&'static str`. +/// +/// String slices are always valid UTF-8. +/// +/// # Examples +/// +/// String literals are string slices: +/// +/// ``` +/// let hello = "Hello, world!"; +/// +/// // with an explicit type annotation +/// let hello: &'static str = "Hello, world!"; +/// ``` +/// +/// They are `'static` because they're stored directly in the final binary, and +/// so will be valid for the `'static` duration. +/// +/// # Representation +/// +/// A `&str` is made up of two components: a pointer to some bytes, and a +/// length. You can look at these with the [`as_ptr`] and [`len`] methods: +/// +/// ``` +/// use std::slice; +/// use std::str; +/// +/// let story = "Once upon a time..."; +/// +/// let ptr = story.as_ptr(); +/// let len = story.len(); +/// +/// // story has nineteen bytes +/// assert_eq!(19, len); +/// +/// // We can re-build a str out of ptr and len. This is all unsafe because +/// // we are responsible for making sure the two components are valid: +/// let s = unsafe { +/// // First, we build a &[u8]... +/// let slice = slice::from_raw_parts(ptr, len); +/// +/// // ... and then convert that slice into a string slice +/// str::from_utf8(slice) +/// }; +/// +/// assert_eq!(s, Ok(story)); +/// ``` +/// +/// [`as_ptr`]: #method.as_ptr +/// [`len`]: #method.len +/// +/// Note: This example shows the internals of `&str`. `unsafe` should not be +/// used to get a string slice under normal circumstances. Use `as_str` +/// instead. +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_str {} + +#[doc(primitive = "tuple")] +#[doc(alias = "(")] +#[doc(alias = ")")] +#[doc(alias = "()")] +// +/// A finite heterogeneous sequence, `(T, U, ..)`. +/// +/// Let's cover each of those in turn: +/// +/// Tuples are *finite*. In other words, a tuple has a length. Here's a tuple +/// of length `3`: +/// +/// ``` +/// ("hello", 5, 'c'); +/// ``` +/// +/// 'Length' is also sometimes called 'arity' here; each tuple of a different +/// length is a different, distinct type. +/// +/// Tuples are *heterogeneous*. This means that each element of the tuple can +/// have a different type. In that tuple above, it has the type: +/// +/// ``` +/// # let _: +/// (&'static str, i32, char) +/// # = ("hello", 5, 'c'); +/// ``` +/// +/// Tuples are a *sequence*. This means that they can be accessed by position; +/// this is called 'tuple indexing', and it looks like this: +/// +/// ```rust +/// let tuple = ("hello", 5, 'c'); +/// +/// assert_eq!(tuple.0, "hello"); +/// assert_eq!(tuple.1, 5); +/// assert_eq!(tuple.2, 'c'); +/// ``` +/// +/// The sequential nature of the tuple applies to its implementations of various +/// traits. For example, in `PartialOrd` and `Ord`, the elements are compared +/// sequentially until the first non-equal set is found. +/// +/// For more about tuples, see [the book](../book/ch03-02-data-types.html#the-tuple-type). +/// +/// # Trait implementations +/// +/// If every type inside a tuple implements one of the following traits, then a +/// tuple itself also implements it. +/// +/// * [`Clone`] +/// * [`Copy`] +/// * [`PartialEq`] +/// * [`Eq`] +/// * [`PartialOrd`] +/// * [`Ord`] +/// * [`Debug`] +/// * [`Default`] +/// * [`Hash`] +/// +/// [`Clone`]: clone/trait.Clone.html +/// [`Copy`]: marker/trait.Copy.html +/// [`PartialEq`]: cmp/trait.PartialEq.html +/// [`Eq`]: cmp/trait.Eq.html +/// [`PartialOrd`]: cmp/trait.PartialOrd.html +/// [`Ord`]: cmp/trait.Ord.html +/// [`Debug`]: fmt/trait.Debug.html +/// [`Default`]: default/trait.Default.html +/// [`Hash`]: hash/trait.Hash.html +/// +/// Due to a temporary restriction in Rust's type system, these traits are only +/// implemented on tuples of arity 12 or less. In the future, this may change. +/// +/// # Examples +/// +/// Basic usage: +/// +/// ``` +/// let tuple = ("hello", 5, 'c'); +/// +/// assert_eq!(tuple.0, "hello"); +/// ``` +/// +/// Tuples are often used as a return type when you want to return more than +/// one value: +/// +/// ``` +/// fn calculate_point() -> (i32, i32) { +/// // Don't do a calculation, that's not the point of the example +/// (4, 5) +/// } +/// +/// let point = calculate_point(); +/// +/// assert_eq!(point.0, 4); +/// assert_eq!(point.1, 5); +/// +/// // Combining this with patterns can be nicer. +/// +/// let (x, y) = calculate_point(); +/// +/// assert_eq!(x, 4); +/// assert_eq!(y, 5); +/// ``` +/// +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_tuple {} + +#[doc(primitive = "f32")] +/// The 32-bit floating point type. +/// +/// *[See also the `std::f32::consts` module](f32/consts/index.html).* +/// +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_f32 {} + +#[doc(primitive = "f64")] +// +/// The 64-bit floating point type. +/// +/// *[See also the `std::f64::consts` module](f64/consts/index.html).* +/// +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_f64 {} + +#[doc(primitive = "i8")] +// +/// The 8-bit signed integer type. +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_i8 {} + +#[doc(primitive = "i16")] +// +/// The 16-bit signed integer type. +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_i16 {} + +#[doc(primitive = "i32")] +// +/// The 32-bit signed integer type. +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_i32 {} + +#[doc(primitive = "i64")] +// +/// The 64-bit signed integer type. +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_i64 {} + +#[doc(primitive = "i128")] +// +/// The 128-bit signed integer type. +#[stable(feature = "i128", since = "1.26.0")] +mod prim_i128 {} + +#[doc(primitive = "u8")] +// +/// The 8-bit unsigned integer type. +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_u8 {} + +#[doc(primitive = "u16")] +// +/// The 16-bit unsigned integer type. +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_u16 {} + +#[doc(primitive = "u32")] +// +/// The 32-bit unsigned integer type. +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_u32 {} + +#[doc(primitive = "u64")] +// +/// The 64-bit unsigned integer type. +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_u64 {} + +#[doc(primitive = "u128")] +// +/// The 128-bit unsigned integer type. +#[stable(feature = "i128", since = "1.26.0")] +mod prim_u128 {} + +#[doc(primitive = "isize")] +// +/// The pointer-sized signed integer type. +/// +/// The size of this primitive is how many bytes it takes to reference any +/// location in memory. For example, on a 32 bit target, this is 4 bytes +/// and on a 64 bit target, this is 8 bytes. +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_isize {} + +#[doc(primitive = "usize")] +// +/// The pointer-sized unsigned integer type. +/// +/// The size of this primitive is how many bytes it takes to reference any +/// location in memory. For example, on a 32 bit target, this is 4 bytes +/// and on a 64 bit target, this is 8 bytes. +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_usize {} + +#[doc(primitive = "reference")] +#[doc(alias = "&")] +// +/// References, both shared and mutable. +/// +/// A reference represents a borrow of some owned value. You can get one by using the `&` or `&mut` +/// operators on a value, or by using a `ref` or `ref mut` pattern. +/// +/// For those familiar with pointers, a reference is just a pointer that is assumed to be +/// aligned, not null, and pointing to memory containing a valid value of `T` - for example, +/// `&bool` can only point to an allocation containing the integer values `1` (`true`) or `0` +/// (`false`), but creating a `&bool` that points to an allocation containing +/// the value `3` causes undefined behaviour. +/// In fact, `Option<&T>` has the same memory representation as a +/// nullable but aligned pointer, and can be passed across FFI boundaries as such. +/// +/// In most cases, references can be used much like the original value. Field access, method +/// calling, and indexing work the same (save for mutability rules, of course). In addition, the +/// comparison operators transparently defer to the referent's implementation, allowing references +/// to be compared the same as owned values. +/// +/// References have a lifetime attached to them, which represents the scope for which the borrow is +/// valid. A lifetime is said to "outlive" another one if its representative scope is as long or +/// longer than the other. The `'static` lifetime is the longest lifetime, which represents the +/// total life of the program. For example, string literals have a `'static` lifetime because the +/// text data is embedded into the binary of the program, rather than in an allocation that needs +/// to be dynamically managed. +/// +/// `&mut T` references can be freely coerced into `&T` references with the same referent type, and +/// references with longer lifetimes can be freely coerced into references with shorter ones. +/// +/// Reference equality by address, instead of comparing the values pointed to, is accomplished via +/// implicit reference-pointer coercion and raw pointer equality via [`ptr::eq`], while +/// [`PartialEq`] compares values. +/// +/// [`ptr::eq`]: ptr/fn.eq.html +/// [`PartialEq`]: cmp/trait.PartialEq.html +/// +/// ``` +/// use std::ptr; +/// +/// let five = 5; +/// let other_five = 5; +/// let five_ref = &five; +/// let same_five_ref = &five; +/// let other_five_ref = &other_five; +/// +/// assert!(five_ref == same_five_ref); +/// assert!(five_ref == other_five_ref); +/// +/// assert!(ptr::eq(five_ref, same_five_ref)); +/// assert!(!ptr::eq(five_ref, other_five_ref)); +/// ``` +/// +/// For more information on how to use references, see [the book's section on "References and +/// Borrowing"][book-refs]. +/// +/// [book-refs]: ../book/ch04-02-references-and-borrowing.html +/// +/// # Trait implementations +/// +/// The following traits are implemented for all `&T`, regardless of the type of its referent: +/// +/// * [`Copy`] +/// * [`Clone`] \(Note that this will not defer to `T`'s `Clone` implementation if it exists!) +/// * [`Deref`] +/// * [`Borrow`] +/// * [`Pointer`] +/// +/// [`Copy`]: marker/trait.Copy.html +/// [`Clone`]: clone/trait.Clone.html +/// [`Deref`]: ops/trait.Deref.html +/// [`Borrow`]: borrow/trait.Borrow.html +/// [`Pointer`]: fmt/trait.Pointer.html +/// +/// `&mut T` references get all of the above except `Copy` and `Clone` (to prevent creating +/// multiple simultaneous mutable borrows), plus the following, regardless of the type of its +/// referent: +/// +/// * [`DerefMut`] +/// * [`BorrowMut`] +/// +/// [`DerefMut`]: ops/trait.DerefMut.html +/// [`BorrowMut`]: borrow/trait.BorrowMut.html +/// +/// The following traits are implemented on `&T` references if the underlying `T` also implements +/// that trait: +/// +/// * All the traits in [`std::fmt`] except [`Pointer`] and [`fmt::Write`] +/// * [`PartialOrd`] +/// * [`Ord`] +/// * [`PartialEq`] +/// * [`Eq`] +/// * [`AsRef`] +/// * [`Fn`] \(in addition, `&T` references get [`FnMut`] and [`FnOnce`] if `T: Fn`) +/// * [`Hash`] +/// * [`ToSocketAddrs`] +/// +/// [`std::fmt`]: fmt/index.html +/// [`fmt::Write`]: fmt/trait.Write.html +/// [`PartialOrd`]: cmp/trait.PartialOrd.html +/// [`Ord`]: cmp/trait.Ord.html +/// [`PartialEq`]: cmp/trait.PartialEq.html +/// [`Eq`]: cmp/trait.Eq.html +/// [`AsRef`]: convert/trait.AsRef.html +/// [`Fn`]: ops/trait.Fn.html +/// [`FnMut`]: ops/trait.FnMut.html +/// [`FnOnce`]: ops/trait.FnOnce.html +/// [`Hash`]: hash/trait.Hash.html +/// [`ToSocketAddrs`]: net/trait.ToSocketAddrs.html +/// +/// `&mut T` references get all of the above except `ToSocketAddrs`, plus the following, if `T` +/// implements that trait: +/// +/// * [`AsMut`] +/// * [`FnMut`] \(in addition, `&mut T` references get [`FnOnce`] if `T: FnMut`) +/// * [`fmt::Write`] +/// * [`Iterator`] +/// * [`DoubleEndedIterator`] +/// * [`ExactSizeIterator`] +/// * [`FusedIterator`] +/// * [`TrustedLen`] +/// * [`Send`] \(note that `&T` references only get `Send` if `T: Sync`) +/// * [`io::Write`] +/// * [`Read`] +/// * [`Seek`] +/// * [`BufRead`] +/// +/// [`AsMut`]: convert/trait.AsMut.html +/// [`Iterator`]: iter/trait.Iterator.html +/// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html +/// [`ExactSizeIterator`]: iter/trait.ExactSizeIterator.html +/// [`FusedIterator`]: iter/trait.FusedIterator.html +/// [`TrustedLen`]: iter/trait.TrustedLen.html +/// [`Send`]: marker/trait.Send.html +/// [`io::Write`]: io/trait.Write.html +/// [`Read`]: io/trait.Read.html +/// [`Seek`]: io/trait.Seek.html +/// [`BufRead`]: io/trait.BufRead.html +/// +/// Note that due to method call deref coercion, simply calling a trait method will act like they +/// work on references as well as they do on owned values! The implementations described here are +/// meant for generic contexts, where the final type `T` is a type parameter or otherwise not +/// locally known. +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_ref {} + +#[doc(primitive = "fn")] +// +/// Function pointers, like `fn(usize) -> bool`. +/// +/// *See also the traits [`Fn`], [`FnMut`], and [`FnOnce`].* +/// +/// [`Fn`]: ops/trait.Fn.html +/// [`FnMut`]: ops/trait.FnMut.html +/// [`FnOnce`]: ops/trait.FnOnce.html +/// +/// Function pointers are pointers that point to *code*, not data. They can be called +/// just like functions. Like references, function pointers are, among other things, assumed to +/// not be null, so if you want to pass a function pointer over FFI and be able to accommodate null +/// pointers, make your type `Option<fn()>` with your required signature. +/// +/// Plain function pointers are obtained by casting either plain functions, or closures that don't +/// capture an environment: +/// +/// ``` +/// fn add_one(x: usize) -> usize { +/// x + 1 +/// } +/// +/// let ptr: fn(usize) -> usize = add_one; +/// assert_eq!(ptr(5), 6); +/// +/// let clos: fn(usize) -> usize = |x| x + 5; +/// assert_eq!(clos(5), 10); +/// ``` +/// +/// In addition to varying based on their signature, function pointers come in two flavors: safe +/// and unsafe. Plain `fn()` function pointers can only point to safe functions, +/// while `unsafe fn()` function pointers can point to safe or unsafe functions. +/// +/// ``` +/// fn add_one(x: usize) -> usize { +/// x + 1 +/// } +/// +/// unsafe fn add_one_unsafely(x: usize) -> usize { +/// x + 1 +/// } +/// +/// let safe_ptr: fn(usize) -> usize = add_one; +/// +/// //ERROR: mismatched types: expected normal fn, found unsafe fn +/// //let bad_ptr: fn(usize) -> usize = add_one_unsafely; +/// +/// let unsafe_ptr: unsafe fn(usize) -> usize = add_one_unsafely; +/// let really_safe_ptr: unsafe fn(usize) -> usize = add_one; +/// ``` +/// +/// On top of that, function pointers can vary based on what ABI they use. This is achieved by +/// adding the `extern` keyword to the type name, followed by the ABI in question. For example, +/// `fn()` is different from `extern "C" fn()`, which itself is different from `extern "stdcall" +/// fn()`, and so on for the various ABIs that Rust supports. Non-`extern` functions have an ABI +/// of `"Rust"`, and `extern` functions without an explicit ABI have an ABI of `"C"`. For more +/// information, see [the nomicon's section on foreign calling conventions][nomicon-abi]. +/// +/// [nomicon-abi]: ../nomicon/ffi.html#foreign-calling-conventions +/// +/// Extern function declarations with the "C" or "cdecl" ABIs can also be *variadic*, allowing them +/// to be called with a variable number of arguments. Normal rust functions, even those with an +/// `extern "ABI"`, cannot be variadic. For more information, see [the nomicon's section on +/// variadic functions][nomicon-variadic]. +/// +/// [nomicon-variadic]: ../nomicon/ffi.html#variadic-functions +/// +/// These markers can be combined, so `unsafe extern "stdcall" fn()` is a valid type. +/// +/// Function pointers implement the following traits: +/// +/// * [`Clone`] +/// * [`PartialEq`] +/// * [`Eq`] +/// * [`PartialOrd`] +/// * [`Ord`] +/// * [`Hash`] +/// * [`Pointer`] +/// * [`Debug`] +/// +/// [`Clone`]: clone/trait.Clone.html +/// [`PartialEq`]: cmp/trait.PartialEq.html +/// [`Eq`]: cmp/trait.Eq.html +/// [`PartialOrd`]: cmp/trait.PartialOrd.html +/// [`Ord`]: cmp/trait.Ord.html +/// [`Hash`]: hash/trait.Hash.html +/// [`Pointer`]: fmt/trait.Pointer.html +/// [`Debug`]: fmt/trait.Debug.html +/// +/// Due to a temporary restriction in Rust's type system, these traits are only implemented on +/// functions that take 12 arguments or less, with the `"Rust"` and `"C"` ABIs. In the future, this +/// may change. +/// +/// In addition, function pointers of *any* signature, ABI, or safety are [`Copy`], and all *safe* +/// function pointers implement [`Fn`], [`FnMut`], and [`FnOnce`]. This works because these traits +/// are specially known to the compiler. +/// +/// [`Copy`]: marker/trait.Copy.html +#[stable(feature = "rust1", since = "1.0.0")] +mod prim_fn {} |