#[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 { 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; /// } /// ``` /// /// 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`] 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`] 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`] is very useful for removing errors, `!` can also be used to remove /// successes as well. If we think of [`Result`] as "if this function returns, it has not /// errored," we get a very intuitive idea of [`Result`] 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`] /// instead: /// /// ```ignore (hypothetical-example) /// fn server_loop() -> Result { /// 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` automatically. /// /// [`String::from_str`]: str/trait.FromStr.html#tymethod.from_str /// [`Result`]: result/enum.Result.html /// [`Result`]: result/enum.Result.html /// [`Result`]: 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::()); /// /// let s = String::from("hello"); /// /// // five elements times one byte per element /// assert_eq!(5, s.len() * std::mem::size_of::()); /// ``` /// /// [`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 = 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, sometimes called "unit" or "nil". /// /// 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 = Box::new(10); /// let my_num_ptr: *const i32 = &*my_num; /// let mut my_speed: Box = 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`). /// /// 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 = Box::new(88); /// let my_speed: *mut i32 = Box::into_raw(my_speed); /// /// // By taking ownership of the original `Box` 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; /// /// fn main() { /// unsafe { /// let my_num: *mut i32 = libc::malloc(mem::size_of::()) 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 sizes from 0 to 32 (inclusive) 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] /// - [`Default`][default] /// /// This limitation on the size `N` exists because Rust does not yet support /// code that is generic over the size of an array type. `[Foo; 3]` and `[Bar; 3]` /// are instances of same generic type `[T; 3]`, but `[Foo; 3]` and `[Foo; 5]` are /// entirely different types. 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() { } /// ``` /// /// If the array has 32 or fewer elements (see above), 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 layed 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` module](f32/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` module](f64/index.html).* /// #[stable(feature = "rust1", since = "1.0.0")] mod prim_f64 { } #[doc(primitive = "i8")] // /// The 8-bit signed integer type. /// /// *[See also the `std::i8` module](i8/index.html).* #[stable(feature = "rust1", since = "1.0.0")] mod prim_i8 { } #[doc(primitive = "i16")] // /// The 16-bit signed integer type. /// /// *[See also the `std::i16` module](i16/index.html).* #[stable(feature = "rust1", since = "1.0.0")] mod prim_i16 { } #[doc(primitive = "i32")] // /// The 32-bit signed integer type. /// /// *[See also the `std::i32` module](i32/index.html).* #[stable(feature = "rust1", since = "1.0.0")] mod prim_i32 { } #[doc(primitive = "i64")] // /// The 64-bit signed integer type. /// /// *[See also the `std::i64` module](i64/index.html).* #[stable(feature = "rust1", since = "1.0.0")] mod prim_i64 { } #[doc(primitive = "i128")] // /// The 128-bit signed integer type. /// /// *[See also the `std::i128` module](i128/index.html).* #[stable(feature = "i128", since="1.26.0")] mod prim_i128 { } #[doc(primitive = "u8")] // /// The 8-bit unsigned integer type. /// /// *[See also the `std::u8` module](u8/index.html).* #[stable(feature = "rust1", since = "1.0.0")] mod prim_u8 { } #[doc(primitive = "u16")] // /// The 16-bit unsigned integer type. /// /// *[See also the `std::u16` module](u16/index.html).* #[stable(feature = "rust1", since = "1.0.0")] mod prim_u16 { } #[doc(primitive = "u32")] // /// The 32-bit unsigned integer type. /// /// *[See also the `std::u32` module](u32/index.html).* #[stable(feature = "rust1", since = "1.0.0")] mod prim_u32 { } #[doc(primitive = "u64")] // /// The 64-bit unsigned integer type. /// /// *[See also the `std::u64` module](u64/index.html).* #[stable(feature = "rust1", since = "1.0.0")] mod prim_u64 { } #[doc(primitive = "u128")] // /// The 128-bit unsigned integer type. /// /// *[See also the `std::u128` module](u128/index.html).* #[stable(feature = "i128", since="1.26.0")] mod prim_u128 { } #[doc(primitive = "isize")] // /// The pointer-sized signed integer type. /// /// *[See also the `std::isize` module](isize/index.html).* /// /// 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. /// /// *[See also the `std::usize` module](usize/index.html).* /// /// 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` 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 { }