Copyright	(c) 2021 Composewell Technologies
License	BSD-3-Clause
Maintainer	streamly@composewell.com
Stability	released
Portability	GHC
Safe Haskell	Safe-Inferred
Language	Haskell2010

Streamly.Data.Fold.Tee

Description

The Tee type is a newtype wrapper over the Fold type providing distributive Applicative, Semigroup, Monoid, Num, Floating and Fractional instances. The input received by the composed Tee is replicated and distributed to both the constituent Tees.

For example, to compute the average of numbers in a stream without going through the stream twice:

>>> import Streamly.Data.Fold.Tee (Tee(..))
>>> import qualified Streamly.Prelude as Stream
>>> import qualified Streamly.Data.Fold as Fold

>>> avg = (/) <$> (Tee Fold.sum) <*> (Tee $ fmap fromIntegral Fold.length)
>>> Stream.fold (toFold avg) $ Stream.fromList [1.0..100.0]
50.5

Similarly, the Semigroup and Monoid instances of Tee distribute the input to both the folds and combine the outputs using Monoid or Semigroup instances of the output types:

>>> import Data.Monoid (Sum(..))
>>> t = Tee Fold.head <> Tee Fold.last
>>> Stream.fold (toFold t) (fmap Sum $ Stream.enumerateFromTo 1.0 100.0)
Just (Sum {getSum = 101.0})

The Num, Floating, and Fractional instances work in the same way.

Synopsis

newtype Tee m a b = Tee {
- toFold :: Fold m a b
}

Documentation

newtype Tee m a b Source #

Tee is a newtype wrapper over the Fold type providing distributing Applicative, Semigroup, Monoid, Num, Floating and Fractional instances.

Since: 0.8.0

Constructors

Tee
Fields toFold :: Fold m a b

Instances

Instances details

Monad m => Applicative (Tee m a) Source #	`<*>` distributes the input to both the argument `Tee`s and combines their outputs using function application.
Instance details Defined in Streamly.Internal.Data.Fold.Tee Methods pure :: a0 -> Tee m a a0 # (<>) :: Tee m a (a0 -> b) -> Tee m a a0 -> Tee m a b # liftA2 :: (a0 -> b -> c) -> Tee m a a0 -> Tee m a b -> Tee m a c # (>) :: Tee m a a0 -> Tee m a b -> Tee m a b # (<*) :: Tee m a a0 -> Tee m a b -> Tee m a a0 #
Functor m => Functor (Tee m a) Source #
Instance details Defined in Streamly.Internal.Data.Fold.Tee Methods fmap :: (a0 -> b) -> Tee m a a0 -> Tee m a b # (<$) :: a0 -> Tee m a b -> Tee m a a0 #
(Semigroup b, Monoid b, Monad m) => Monoid (Tee m a b) Source #	`<>` distributes the input to both the argument `Tee`s and combines their outputs using the `Monoid` instance of the output type.
Instance details Defined in Streamly.Internal.Data.Fold.Tee Methods mempty :: Tee m a b # mappend :: Tee m a b -> Tee m a b -> Tee m a b # mconcat :: [Tee m a b] -> Tee m a b #
(Semigroup b, Monad m) => Semigroup (Tee m a b) Source #	`<>` distributes the input to both the argument `Tee`s and combines their outputs using the `Semigroup` instance of the output type.
Instance details Defined in Streamly.Internal.Data.Fold.Tee Methods (<>) :: Tee m a b -> Tee m a b -> Tee m a b # sconcat :: NonEmpty (Tee m a b) -> Tee m a b # stimes :: Integral b0 => b0 -> Tee m a b -> Tee m a b #
(Monad m, Floating b) => Floating (Tee m a b) Source #	Binary `Floating` operations distribute the input to both the argument `Tee`s and combine their outputs using the `Floating` instance of the output type.
Instance details Defined in Streamly.Internal.Data.Fold.Tee Methods pi :: Tee m a b # exp :: Tee m a b -> Tee m a b # log :: Tee m a b -> Tee m a b # sqrt :: Tee m a b -> Tee m a b # (**) :: Tee m a b -> Tee m a b -> Tee m a b # logBase :: Tee m a b -> Tee m a b -> Tee m a b # sin :: Tee m a b -> Tee m a b # cos :: Tee m a b -> Tee m a b # tan :: Tee m a b -> Tee m a b # asin :: Tee m a b -> Tee m a b # acos :: Tee m a b -> Tee m a b # atan :: Tee m a b -> Tee m a b # sinh :: Tee m a b -> Tee m a b # cosh :: Tee m a b -> Tee m a b # tanh :: Tee m a b -> Tee m a b # asinh :: Tee m a b -> Tee m a b # acosh :: Tee m a b -> Tee m a b # atanh :: Tee m a b -> Tee m a b # log1p :: Tee m a b -> Tee m a b # expm1 :: Tee m a b -> Tee m a b # log1pexp :: Tee m a b -> Tee m a b # log1mexp :: Tee m a b -> Tee m a b #
(Monad m, Num b) => Num (Tee m a b) Source #	Binary `Num` operations distribute the input to both the argument `Tee`s and combine their outputs using the `Num` instance of the output type.
Instance details Defined in Streamly.Internal.Data.Fold.Tee Methods (+) :: Tee m a b -> Tee m a b -> Tee m a b # (-) :: Tee m a b -> Tee m a b -> Tee m a b # (*) :: Tee m a b -> Tee m a b -> Tee m a b # negate :: Tee m a b -> Tee m a b # abs :: Tee m a b -> Tee m a b # signum :: Tee m a b -> Tee m a b # fromInteger :: Integer -> Tee m a b #
(Monad m, Fractional b) => Fractional (Tee m a b) Source #	Binary `Fractional` operations distribute the input to both the argument `Tee`s and combine their outputs using the `Fractional` instance of the output type.
Instance details Defined in Streamly.Internal.Data.Fold.Tee Methods (/) :: Tee m a b -> Tee m a b -> Tee m a b # recip :: Tee m a b -> Tee m a b # fromRational :: Rational -> Tee m a b #