Lens.Family.THCore

The shared functionality behind Lens.Family.TH and Lens.Family2.TH.

Documentation

defaultNameTransform :: String -> Maybe String

By default, if the field name begins with an underscore, then the underscore will simply be removed (and the new first character lowercased if necessary).

type LensTypeInfo = (Name, [TyVarBndr])

Information about the larger type the lens will operate on.

type ConstructorFieldInfo = (Name, Strict, Type)

Information about the smaller type the lens will operate on.

deriveLenses

Arguments

:: (Name -> LensTypeInfo -> ConstructorFieldInfo -> Q [Dec])

the signature deriver

-> (String -> Maybe String)

the name transformer

-> Name

-> Q [Dec]

The true workhorse of lens derivation. This macro is parameterized by a macro that derives signatures, as well as a function that filters and transforms names. Producing Nothing means that a lens should not be generated for the provided name.

makeTraversals :: Name -> Q [Dec]

Derive traversals for each constructor in a data or newtype declaration, Traversals will be named by prefixing the constructor name with an underscore.

Example usage:

$(makeTraversals ''Foo)