Data.Operator.Eq
- Package
- purescript-higher-order
- Repository
- matthew-hilty/purescript-higher-order
#Eq1 Source
class Eq1 f whereThe Eq1 typeclass of this module represents type constructors f that
have an associated equivalence relation of values of type f a
independent of any choice of a.
Unlike the Data.Eq.Eq1 typeclass of the 'Prelude' module [hereafter,
qualified by the prefix "Prelude"], Eq1, defined here, is not generally
equivalent to the Eq typeclass (also found in the 'Prelude' module).
For example, whereas both
eq (Cons 0 Nil) (Cons 1 Nil) == false
and
Prelude.eq1 (Cons 0 Nil) (Cons 1 Nil) == false
the definition found in this module gives the following:
eq1 (Cons 0 Nil) (Cons 1 Nil) == true
That is, the Int values in a value of List Int (and, more generally,
the a values in any List a) have little relevance in determining the
results of the eq1 function.
The instances of the Eq1 typeclass of this module are designed to
emphasize the value-level effects of the type constructors themselves.
In practice, this often means that an equivalence relation is assigned to
the type constructor's data constructors. The Eq1 instance declaration
for List, for example, effectively projects any value of type List a
into one of two equivalence classes, where the specific equivalence-class
assignment is determined by the data constructor (Cons or Nil) of the
value's head deconstruction.
This interpretation of Eq1 exists in addition to Prelude.Eq1
because datatypes often have intrinsic (or designed) subgroupings,
commonly distingished by data constructors, and a means to relate these
different subgroupings can be useful -- especially in concert with
PartialOrd1 and other related typeclasses.
Members
Instances
#GenericEq1 Source
class GenericEq1 a whereMembers
genericEq1 :: a -> a -> Boolean
Instances
(GenericEq1 b) => GenericEq1 (Sum a b)(GenericEq1 a) => GenericEq1 (Product a b)GenericEq1 (Constructor name a)