src/doc/reference/src/items/structs.md

   1 # Structs
   2
   3 > **<sup>Syntax</sup>**
   4 > _Struct_ :
   5 > &nbsp;&nbsp; &nbsp;&nbsp; _StructStruct_
   6 > &nbsp;&nbsp; | _TupleStruct_
   7 >
   8 > _StructStruct_ :
   9 > &nbsp;&nbsp; `struct`
  10 >   [IDENTIFIER]&nbsp;
  11 >   [_Generics_]<sup>?</sup>
  12 >   [_WhereClause_]<sup>?</sup>
  13 >   ( `{` _StructFields_<sup>?</sup> `}` | `;` )
  14 >
  15 > _TupleStruct_ :
  16 > &nbsp;&nbsp; `struct`
  17 >   [IDENTIFIER]&nbsp;
  18 >   [_Generics_]<sup>?</sup>
  19 >   `(` _TupleFields_<sup>?</sup> `)`
  20 >   [_WhereClause_]<sup>?</sup>
  21 >   `;`
  22 >
  23 > _StructFields_ :
  24 > &nbsp;&nbsp; _StructField_ (`,` _StructField_)<sup>\*</sup> `,`<sup>?</sup>
  25 >
  26 > _StructField_ :
  27 > &nbsp;&nbsp; [_OuterAttribute_]<sup>\*</sup>
  28 > &nbsp;&nbsp; [_Visibility_]
  29 > &nbsp;&nbsp; [IDENTIFIER] `:` [_Type_]
  30 >
  31 > _TupleFields_ :
  32 > &nbsp;&nbsp; _TupleField_ (`,` _TupleField_)<sup>\*</sup> `,`<sup>?</sup>
  33 >
  34 > _TupleField_ :
  35 > &nbsp;&nbsp; [_OuterAttribute_]<sup>\*</sup>
  36 > &nbsp;&nbsp; [_Visibility_]
  37 > &nbsp;&nbsp; [_Type_]
  38
  39 A _struct_ is a nominal [struct type] defined with the keyword `struct`.
  40
  41 An example of a `struct` item and its use:
  42
  43 ```rust
  44 struct Point {x: i32, y: i32}
  45 let p = Point {x: 10, y: 11};
  46 let px: i32 = p.x;
  47 ```
  48
  49 A _tuple struct_ is a nominal [tuple type], also defined with the keyword
  50 `struct`. For example:
  51
  52 [struct type]: types.html#struct-types
  53 [tuple type]: types.html#tuple-types
  54
  55 ```rust
  56 struct Point(i32, i32);
  57 let p = Point(10, 11);
  58 let px: i32 = match p { Point(x, _) => x };
  59 ```
  60
  61 A _unit-like struct_ is a struct without any fields, defined by leaving off the
  62 list of fields entirely. Such a struct implicitly defines a constant of its
  63 type with the same name. For example:
  64
  65 ```rust
  66 struct Cookie;
  67 let c = [Cookie, Cookie {}, Cookie, Cookie {}];
  68 ```
  69
  70 is equivalent to
  71
  72 ```rust
  73 struct Cookie {}
  74 const Cookie: Cookie = Cookie {};
  75 let c = [Cookie, Cookie {}, Cookie, Cookie {}];
  76 ```
  77
  78 The precise memory layout of a struct is not specified. One can specify a
  79 particular layout using the [`repr` attribute].
  80
  81 [`repr` attribute]: attributes.html#ffi-attributes
  82
  83 [_OuterAttribute_]: attributes.html
  84 [IDENTIFIER]: identifiers.html
  85 [_Generics_]: items.html#type-parameters
  86 [_WhereClause_]: items.html#type-parameters
  87 [_Visibility_]: visibility-and-privacy.html
  88 [_Type_]: types.html