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GHC 10.0.0.20260917 · lts/ghc-10.0.x · 77a8662 · 2026-10-31

Modulederiving-compat-0.6.8Haskell2010

Data.Functor.Deriving

Exports functions to mechanically derive Functor instances.

For more info on how deriving Functor works, see this GHC wiki page.

Contents

Functor
FFTOptions
deriveFunctor limitations

Synopsis

value deriveFunctor
value deriveFunctorOptions
value makeFmap
value makeFmapOptions
value makeReplace
value makeReplaceOptions
newtype FFTOptions
value defaultFFTOptions

Packagederiving-compat-0.6.8
Exports8
LanguageHaskell2010
LicenceBSD-3-Clause
SourceDeriving.hs

Functor

valuederiveFunctor :: Name -> Q [Dec]

Generates a Functor instance declaration for the given data type or data family instance.

valuederiveFunctorOptions :: FFTOptions -> Name -> Q [Dec]

Like deriveFunctor, but takes an FFTOptions argument.

valuemakeFmap :: Name -> Q Exp

Generates a lambda expression which behaves like fmap (without requiring a Functor instance).

valuemakeFmapOptions :: FFTOptions -> Name -> Q Exp

Like makeFmap, but takes an FFTOptions argument.

valuemakeReplace :: Name -> Q Exp

Generates a lambda expression which behaves like (<$) (without requiring a Functor instance).

valuemakeReplaceOptions :: FFTOptions -> Name -> Q Exp

Like makeReplace, but takes an FFTOptions argument.

FFTOptions

newtypenewtype FFTOptions

Options that further configure how the functions in Data.Functor.Deriving should behave. (FFT stands for FunctorFoldableTraversable.)

Constructors

FFTOptions
- fftEmptyCaseBehavior :: Bool
  If True, derived instances for empty data types (i.e., ones with no data constructors) will use the EmptyCase language extension. If False, derived instances will simply use seq instead. (This has no effect on GHCs before 7.8, since EmptyCase is only available in 7.8 or later.)

Instances4Eq, Ord, Read, Show

Eq FFTOptionsDefined in deriving-compat-0.6.8 · Data.Functor.Deriving.Internal
Ord FFTOptionsDefined in deriving-compat-0.6.8 · Data.Functor.Deriving.Internal
Read FFTOptionsDefined in deriving-compat-0.6.8 · Data.Functor.Deriving.Internal
Show FFTOptionsDefined in deriving-compat-0.6.8 · Data.Functor.Deriving.Internal

valuedefaultFFTOptions :: FFTOptions

Conservative FFTOptions that doesn't attempt to use EmptyCase (to prevent users from having to enable that extension at use sites.)

deriveFunctor limitations

Be aware of the following potential gotchas:

Type variables of kind * -> * are assumed to have Functor constraints. If this is not desirable, use makeFmap.