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+title = "`struct`"
+weight = 1
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+
+Defines a record type (a "pure product"). This is a specialized form of
+a `data` definition. The same field name may occur in more than one
+type.
+
+```
+topDefn  ::= struct typeId {tyVarId }= { { fieldDef ; }} [ derive ]
+fieldDef ::= fieldId :: type
+```
+
+Example:
+
+```
+struct Proc  = { pc :: Addr; rf :: RegFile; mem :: Memory }
+struct Coord = { x :: Int; y :: Int }
+```
+
+
+Section [5.6](fixme) describes how to construct values of a
+`struct` type. A field of a `struct` type can be extracted either
+directly using "dot" notation (section
+[5.7](fixme)) or using pattern matching (section
+[6.3](fixme)).
+
+
+### Tuples {#sec-tuple-type}
+
+
+One way to group multiple values together is to use a `data` definition
+in which a constructor has multiple fields.
+
+
+However, there is a built-in notation for a common form of grouping,
+called "tuples". To group two (or more) values together the Prelude
+contains a type, `PrimPair`, for which there is syntactic sugar for type
+expressions, value expressions, and patterns.
+
+The type has the following definition
+
+```hs
+struct PrimPair a b = { fst :: a; snd :: b } deriving (Eq, Bits, Bounded)
+```
+
+For type expressions the following shorthand can be used:
+
+(a, b) $\equiv$ PrimPair a b
+
+Or, more generally,
+
+($t_1$, $t_2$, $\cdots$, $t_n$) $\equiv$ PrimPair $t_1$ (PrimPair $t_2$ ($\cdots$ $t_n$))
+
+
+There is a corresponding shorthand for value expressions and patterns:
+
+(a, b) $\equiv$ PrimPair { fst = a; snd = b }
+
+There is also special syntax for the empty tuple. It is written "`()`"
+for types, expressions, and patterns. The real type has the following
+definition
+
+```hs
+struct PrimUnit = { } deriving (Eq, Bits, Bounded)
+```
+