| | 17 | |
| | 18 | == Terminology == |
| | 19 | |
| | 20 | |
| | 21 | '''Data-type family''': a data type declared with a `data family` or `newtype family` declaration. |
| | 22 | |
| | 23 | '''Type-synonym family''', or '''type function''': a type synonym declared with a `type family` declaration. |
| | 24 | |
| | 25 | '''Type family''': a data-type family or type-synonym family. |
| | 26 | |
| | 27 | '''Parametric type constructors''': Type constructors in vanilla Haskell. |
| | 28 | |
| | 29 | '''Family type constructor''' or '''Family `TyCon`''': the type constructor for a type family. |
| | 30 | |
| | 31 | '''Instance `TyCon`''': the `TyCon` arising from a `data instance` or `newtype instance` declaration. Sometimes called the '''representation `TyCon`'''. The instance `TyCon` is invisible to the programmer; it is only used internally inside GHC. (NB: a `type instance` declaration does not give rise to a new `TyCon`.) |
| | 32 | |
| | 33 | '''Associated type''': A type family that is declared in a type class. |
| | 34 | |
| | 35 | '''Kind signature''': Declaration of the name, kind, and arity of an indexed type constructor. The ''arity'' is the number of type indexes - ''not'' the overall number of parameters - of an indexed type constructor. |
| | 36 | |
| | 37 | '''Definitions vs. declarations''': We sometimes call the kind signature of an indexed constructor its ''declaration'' and the subsequent population of the type family by type equations or indexed data/newtype declarations the constructor's ''definition''. |
| 50 | | == Terminology == |
| 51 | | |
| 52 | | '''Parametric type constructors''': Type constructors in vanilla Haskell. |
| 53 | | |
| 54 | | '''Indexed type constructors''': Type constructors that are defined via one or more type declarations that have non-variable parameters. We often call them sloppily just ''indexed types''. We informally call constructors that are not indexed ''vanilla'' constructors. |
| 55 | | |
| 56 | | '''Kind signature''': Declaration of the name, kind, and arity of an indexed type constructor. The ''arity'' is the number of type indexes - ''not'' the overall number of parameters - of an indexed type constructor. |
| 57 | | |
| 58 | | '''Type function''': An indexed type synonym. |
| 59 | | |
| 60 | | '''Indexed data type''': An indexed type constructor declared with `data` or `newtype`. |
| 61 | | |
| 62 | | '''Associated type''': An indexed type that is declared in a type class. |
| 63 | | |
| 64 | | '''Type family''': Indexed types can be regarded as families of types; especially in the case of indexed data types, we call each declaration at a particular type index as ''member'' or ''element'' of that family. |
| 65 | | |
| 66 | | '''Definitions vs. declarations''': We sometimes call the kind signature of an indexed constructor its ''declaration'' and the subsequent population of the type family by type equations or indexed data/newtype declarations the constructor's ''definition''. |
| 67 | | |
