Changes between Version 76 and Version 77 of TypeFunctions


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Timestamp:
May 14, 2007 12:18:45 PM (7 years ago)
Author:
chak
Comment:

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  • TypeFunctions

    v76 v77  
    5656 * Applications of type functions need to supply all indexes after unfolding of all ordinary type synonyms.  (This is the same saturation requirement that we already have on ordinary type synonyms.) 
    5757 * Instances of data families and equations of type functions have the keyword `instance` after the first keyword.  They otherwise have the same form as ordinary data type/newtype and type synonym declarations, respectively, but can have non-variable type indexes as arguments.  Type indexes can include applications of data families, but no type functions. 
    58  * Instances of type families are only valid if a kind signature for the type constructor is in scope.  The kind of an indexed type is solely determined from the kind signature.  Instances must conform to this kind.  In particular, the argument count of data and newtype instances must match the arity indicated by the kind.  The number of arguments of a type equation must be equal to the number of type indexes (i.e., type variables in the head) of the family declaration. 
     58 * Instances of type families are only valid if a kind signature for the type constructor is in scope.  The kind of an indexed type is solely determined from the kind signature.  Instances must conform to this kind.  In particular, the argument count of data and newtype instances must match the arity indicated by the kind.  The number of arguments of a type equation must be equal to the number of type indexes (i.e., type variables in the head) of the family declaration.  Instances of data families can be both data types or newtypes (or a mix of the two). 
    5959 * Data family instances can have deriving clauses as usual (but they do not support the non-standard deriving of `Typeable`). 
    6060 * Associated types are type families declared as part of a type class.  The syntax of family declarations in class declarations and of type instance declarations in instance declarations is as for toplevel declarations, but without the `family` and `instance` keywords.