Structs - The Rust Reference

# Structs

> Syntax
> Struct :
> StructStruct
> | TupleStruct

> StructStruct :
> `struct` IDENTIFIER Generics? WhereClause? ( `{` StructFields? `}` | `;` )

> TupleStruct :
> `struct` IDENTIFIER Generics? `(` TupleFields? `)` WhereClause? `;`

> StructFields :
> StructField (`,` StructField)* `,`?

> StructField :
> OuterAttribute*
> Visibility IDENTIFIER `:` Type

> TupleFields :
> TupleField (`,` TupleField)* `,`?

> TupleField :
> OuterAttribute*
> Visibility Type

A struct is a nominal struct type defined with the keyword `struct`.

An example of a `struct` item and its use:

    # #![allow(unused_variables)]
    #fn main() {
    struct Point {x: i32, y: i32}
    let p = Point {x: 10, y: 11};
    let px: i32 = p.x;
    #}

A tuple struct is a nominal tuple type, also defined with the keyword `struct`. For example:

    # #![allow(unused_variables)]
    #fn main() {
    struct Point(i32, i32);
    let p = Point(10, 11);
    let px: i32 = match p { Point(x, _) => x };
    #}

A unit-like struct is a struct without any fields, defined by leaving off the list of fields entirely. Such a struct implicitly defines a constant of its type with the same name. For example:

    # #![allow(unused_variables)]
    #fn main() {
    struct Cookie;
    let c = [Cookie, Cookie {}, Cookie, Cookie {}];
    #}

is equivalent to

    # #![allow(unused_variables)]
    #fn main() {
    struct Cookie {}
    const Cookie: Cookie = Cookie {};
    let c = [Cookie, Cookie {}, Cookie, Cookie {}];
    #}

The precise memory layout of a struct is not specified. One can specify a particular layout using the `repr` attribute.