Documentation

The Repr type class denotes that a type can be decomposed to a representation built out of pieces for which the TrieKey class defines a generalized trie structure.

It is required that, if (Repr a, Eq a), and x, y :: a, then x == y if and only if toRep x == toRep y. It is typically the case that compare x y == compare (toRep x) (toRep y), as well, but this is not strictly required. (It is, however, the case for all instances built into the package.)

As an additional note, the Key modifier is used for "bootstrapping" Repr instances, allowing a type to be used in its own Repr definition when wrapped in a Key modifier.

Given the name of a type constructor, automatically generates an efficient Repr instance. If you have several mutually dependent (or even mutually recursive) types, genRepr will construct instances for all of them.

genRepr guarantees that any instances it generates are consistent with the ordering that would be generated by deriving (Ord) in the data declaration. That is, if genRepr generates an instance Repr a, then it is guaranteed that if x, y :: a, and a has a derived Ord instance, then compare x y == compare (toRep x) (toRep y).

Given the name of a type constructor, automatically generates an efficient Repr instance. If you have several mutually dependent (or even mutually recursive) types, genOptRepr will construct instances for all of them. The instance generated by genOptRepr may, in some cases, be more efficient than the instance generated by genRepr -- in particular, arguments common to several constructors may be factored out, reducing the complexity of the associated TrieKey instance, but leaving an ordering inconsistent with Ord.

Therefore, genOptRepr guarantees that any instances it generates are consistent with the ordering that would be generated by deriving (Eq) in the data declaration. That is, if genOptRepr generates an instance Repr a, then it is guaranteed that if x, y :: a, and a has a derived Eq instance, then (x == y) == (toRep x == toRep y).

Given a type with an associated Ord instance, generates a representation that will cause its TMap implementation to be essentially equivalent to Data.Map.