- class Monoid m => Reducer c m where
- foldMapReduce :: (Foldable f, Reducer e m) => (a -> e) -> f a -> m
- foldReduce :: (Foldable f, Reducer e m) => f e -> m
- pureUnit :: (Applicative f, Reducer c n) => c -> f n
- returnUnit :: (Monad m, Reducer c n) => c -> m n
Documentation
class Monoid m => Reducer c m whereSource
This type may be best read infix. A c
is a Reducer
mMonoid
m
that maps
values of type c
through unit
to values of type m
. A c
-Reducer
may also
supply operations which tack-on another c
to an existing Monoid
m
on the left
or right. These specialized reductions may be more efficient in some scenarios
and are used when appropriate by a Generator
. The names cons
and snoc
work
by analogy to the synonymous operations in the list monoid.
This class deliberately avoids functional-dependencies, so that () can be a c
-Reducer
for all c
, and so many common reducers can work over multiple types, for instance,
First and Last may reduce both a
and Maybe
a
. Since a Generator
has a fixed element
type, the input to the reducer is generally known and extracting from the monoid usually
is sufficient to fix the result type. Combinators are available for most scenarios where
this is not the case, and the few remaining cases can be handled by using an explicit
type annotation.
Convert a value into a Monoid
Append a value to a Monoid
for use in left-to-right reduction
Prepend a value onto a Monoid
for use during right-to-left reduction
Reducer Bool All | |
Reducer Bool Any | |
Reducer c () | |
Reducer ByteString ByteString | |
Reducer ByteString ByteString | |
Reducer ByteString Body | |
Reducer a (Last a) | |
Reducer a (First a) | |
Num a => Reducer a (Product a) | |
Num a => Reducer a (Sum a) | |
Monoid a => Reducer a (Dual a) | |
Reducer c [c] | |
(Packable a, Annotation m) => Reducer a (Rope m) | |
Measured v a => Reducer a (FingerTree v a) | |
(Reducer c m, Reducer c n) => Reducer c (m, n) | |
(Reducer c a, Reducer c b) => Reducer c (:*: a b) | |
(Reducer c m, Reducer c n, Reducer c o) => Reducer c (m, n, o) | |
(Reducer c m, Reducer c n, Reducer c o, Reducer c p) => Reducer c (m, n, o, p) | |
Reducer (Maybe a) (Last a) | |
Reducer (Maybe a) (First a) | |
Reducer (a -> a) (Endo a) |
Folding with Reducer
s
foldMapReduce :: (Foldable f, Reducer e m) => (a -> e) -> f a -> mSource
foldReduce :: (Foldable f, Reducer e m) => f e -> mSource
Applicative
reduction
pureUnit :: (Applicative f, Reducer c n) => c -> f nSource
returnUnit :: (Monad m, Reducer c n) => c -> m nSource