Safe Haskell | Safe |
---|---|
Language | Haskell98 |
Generics.Deriving.Monoid
Description
This module provides two main features:
GMonoid
, a generic version of theMonoid
type class, including instances of the types from Data.Monoid- Default generic definitions for the
Monoid
methodsmempty
andmappend
The generic defaults only work for types without alternatives (i.e. they have only one constructor). We cannot in general know how to deal with different constructors.
- class GMonoid a where
- gmemptydefault :: (Generic a, GMonoid' (Rep a)) => a
- gmappenddefault :: (Generic a, GMonoid' (Rep a)) => a -> a -> a
- memptydefault :: (Generic a, Monoid' (Rep a)) => a
- mappenddefault :: (Generic a, Monoid' (Rep a)) => a -> a -> a
- module Data.Monoid
GMonoid type class
Methods
Generic mempty
Generic mappend
Generic mconcat
gmempty :: (Generic a, GMonoid' (Rep a)) => a #
Generic mempty
gmappend :: (Generic a, GMonoid' (Rep a)) => a -> a -> a #
Generic mappend
Instances
Default definitions
GMonoid
gmemptydefault :: (Generic a, GMonoid' (Rep a)) => a #
gmappenddefault :: (Generic a, GMonoid' (Rep a)) => a -> a -> a #
Monoid
These functions can be used in a Monoid
instance. For example:
-- LANGUAGE DeriveGeneric import Generics.Deriving.Base (Generic) import Generics.Deriving.Monoid data T a = C a (Maybe a) deriving Generic instance Monoid a => Monoid (T a) where mempty = memptydefault mappend = mappenddefault
memptydefault :: (Generic a, Monoid' (Rep a)) => a #
mappenddefault :: (Generic a, Monoid' (Rep a)) => a -> a -> a #
The Monoid module
This is exported for convenient access to the various wrapper types.
module Data.Monoid