Safe Haskell | Safe |
---|---|

Language | Haskell2010 |

Element-agnostic grouping utilities for `pipes`

See Pipes.Group.Tutorial for an extended tutorial

Some type signatures below refer to the aliases below, which are not used in this library, but are included to simplify the documentation.

type Groups a m x =`FreeT`

(`Producer`

a m) m x type Splitter a m x =`Producer`

a m x -> Groups a m x type Transformation a m x = Groups a m x -> Groups a m x type Joiner a m x = Groups a m x ->`Producer`

a m x

- groups :: (Monad m, Eq a') => Lens (Producer a' m x) (Producer a m x) (FreeT (Producer a' m) m x) (FreeT (Producer a m) m x)
- groupsBy :: Monad m => (a' -> a' -> Bool) -> Lens (Producer a' m x) (Producer a m x) (FreeT (Producer a' m) m x) (FreeT (Producer a m) m x)
- groupsBy' :: Monad m => (a' -> a' -> Bool) -> Lens (Producer a' m x) (Producer a m x) (FreeT (Producer a' m) m x) (FreeT (Producer a m) m x)
- chunksOf :: Monad m => Int -> Lens (Producer a' m x) (Producer a m x) (FreeT (Producer a' m) m x) (FreeT (Producer a m) m x)
- takes :: (Functor f, Monad m) => Int -> FreeT f m () -> FreeT f m ()
- takes' :: Monad m => Int -> FreeT (Producer a m) m x -> FreeT (Producer a m) m x
- drops :: Monad m => Int -> FreeT (Producer a m) m x -> FreeT (Producer a m) m x
- maps :: (Monad m, Functor g) => (forall r. f r -> g r) -> FreeT f m x -> FreeT g m x
- individually :: (Monad m, Functor g) => Setter (FreeT f m x) (FreeT g m x) (f (FreeT f m x)) (g (FreeT f m x))
- concats :: Monad m => FreeT (Producer a m) m x -> Producer a m x
- intercalates :: Monad m => Producer a m () -> FreeT (Producer a m) m x -> Producer a m x
- folds :: Monad m => (x -> a -> x) -> x -> (x -> b) -> FreeT (Producer a m) m r -> Producer b m r
- foldsM :: Monad m => (x -> a -> m x) -> m x -> (x -> m b) -> FreeT (Producer a m) m r -> Producer b m r
- module Control.Monad.Trans.Class
- module Control.Monad.Trans.Free
- module Pipes

# Lenses

groups :: (Monad m, Eq a') => Lens (Producer a' m x) (Producer a m x) (FreeT (Producer a' m) m x) (FreeT (Producer a m) m x) #

Like `groupsBy`

, where the equality predicate is (`==`

)

groups :: Monad m => Lens' (`Producer`

a m x) (Groups a m x) view groups :: Monad m => Splitter a m x set groups :: Monad m => Groups a m x ->`Producer`

a m x ->`Producer`

a m x over groups :: Monad m => Transformation a m x ->`Producer`

a m x ->`Producer`

a m x

`>>>`

`import Lens.Family (view)`

`>>>`

`import Pipes (yield, each)`

`>>>`

`import Pipes.Prelude (toList)`

`>>>`

"1|22|333|4|5"`(toList . intercalates (yield '|') . view groups) (each "12233345")`

groupsBy :: Monad m => (a' -> a' -> Bool) -> Lens (Producer a' m x) (Producer a m x) (FreeT (Producer a' m) m x) (FreeT (Producer a m) m x) #

`groupsBy`

splits a `Producer`

into a `FreeT`

of `Producer`

s grouped using
the given equality predicate

groupsBy p :: Monad m => Lens' (`Producer`

a m x) (Groups a m x) view (groupsBy p) :: Monad m => Splitter a m x set (groupsBy p) :: Monad m => Groups a m x ->`Producer`

a m x ->`Producer`

a m x over (groupsBy p) :: Monad m => Transformation a m x ->`Producer`

a m x ->`Producer`

a m x

`>>>`

`import Lens.Family (view)`

`>>>`

`import Pipes (yield, each)`

`>>>`

`import Pipes.Prelude (toList)`

`>>>`

"1|22|333|4|5"`(toList . intercalates (yield '|') . view (groupsBy (==))) (each "12233345")`

groupsBy' :: Monad m => (a' -> a' -> Bool) -> Lens (Producer a' m x) (Producer a m x) (FreeT (Producer a' m) m x) (FreeT (Producer a m) m x) #

`groupsBy'`

splits a `Producer`

into a `FreeT`

of `Producer`

s grouped using
the given equality predicate

This differs from `groupsBy`

by comparing successive elements for equality
instead of comparing each element to the first member of the group

`>>>`

`import Lens.Family (view)`

`>>>`

`import Pipes (yield, each)`

`>>>`

`import Pipes.Prelude (toList)`

`>>>`

`let cmp c1 c2 = succ c1 == c2`

`>>>`

"12|23|3|345"`(toList . intercalates (yield '|') . view (groupsBy' cmp)) (each "12233345")`

`>>>`

"122|3|3|34|5"`(toList . intercalates (yield '|') . view (groupsBy cmp)) (each "12233345")`

groupsBy' p :: Monad m => Lens' (`Producer`

a m x) (Groups a m x) view (groupsBy' p) :: Monad m => Splitter a m x set (groupsBy' p) :: Monad m => Groups a m x ->`Producer`

a m x ->`Producer`

a m x over (groupsBy' p) :: Monad m => Transformation a m x ->`Producer`

a m x ->`Producer`

a m x

chunksOf :: Monad m => Int -> Lens (Producer a' m x) (Producer a m x) (FreeT (Producer a' m) m x) (FreeT (Producer a m) m x) #

`chunksOf`

is an splits a `Producer`

into a `FreeT`

of `Producer`

s of fixed
length

chunksOf n :: Monad m => Lens' (`Producer`

a m x) (Groups a m x) view (chunksOf n) :: Monad m => Splitter a m x set (chunksOf n) :: Monad m => Groups a m x ->`Producer`

a m x ->`Producer`

a m x over (chunksOf n) :: Monad m => Transformation a m x ->`Producer`

a m x ->`Producer`

a m x

`>>>`

`import Lens.Family (view)`

`>>>`

`import Pipes (yield, each)`

`>>>`

`import Pipes.Prelude (toList)`

`>>>`

"122|333|45"`(toList . intercalates (yield '|') . view (chunksOf 3)) (each "12233345")`

# Transformations

takes :: (Functor f, Monad m) => Int -> FreeT f m () -> FreeT f m () #

`(takes n)`

only keeps the first `n`

functor layers of a `FreeT`

takes :: Monad m => Int -> Groups a m () -> Groups a m ()

`>>>`

`import Lens.Family (view)`

`>>>`

`import Pipes (yield, each)`

`>>>`

`import Pipes.Prelude (toList)`

`>>>`

"1|22|333"`(toList . intercalates (yield '|') . takes 3 . view groups) (each "12233345")`

drops :: Monad m => Int -> FreeT (Producer a m) m x -> FreeT (Producer a m) m x #

`(drops n)`

peels off the first `n`

`Producer`

layers of a `FreeT`

drops :: Monad m => Int -> Transformation a m x

`>>>`

`import Lens.Family (view)`

`>>>`

`import Pipes (yield, each)`

`>>>`

`import Pipes.Prelude (toList)`

`>>>`

"4|5"`(toList . intercalates (yield '|') . drops 3 . view groups) (each "12233345")`

**Use carefully**: the peeling off is not free. This runs the first `n`

layers, just discarding everything they produce.

maps :: (Monad m, Functor g) => (forall r. f r -> g r) -> FreeT f m x -> FreeT g m x #

Transform each individual functor layer of a `FreeT`

You can think of this as:

maps :: (forall r . Producer a m r -> Producer b m r) -> FreeT (Producer a m) m x -> FreeT (Producer b m) m x

This is just a synonym for `transFreeT`

individually :: (Monad m, Functor g) => Setter (FreeT f m x) (FreeT g m x) (f (FreeT f m x)) (g (FreeT f m x)) #

Lens to transform each individual functor layer of a `FreeT`

. (```
over
```

) is equivalent to `individually`

`maps`

, but with a less general type.

`type Group a m x = ``Producer`

a m (Groups a m x)
set individually :: Monad m => Group a m x -> Transformation a m x
over individually :: Monad m => (Group a m x -> Group a m x) -> Transformation a m x

# Joiners

# Folds

These folds are designed to be compatible with the `foldl`

library. See
the `purely`

and `impurely`

functions from that
library for more details.

For example, to count the number of `Producer`

layers in a `FreeT`

, you can
write:

import Control.Applicative (pure) import qualified Control.Foldl as L import Pipes.Group import qualified Pipes.Prelude as P count :: Monad m => FreeT (Producer a m) m () -> m Int count = P.sum . L.purely folds (pure 1)

# Re-exports

Control.Monad.Trans.Class re-exports `lift`

.

Control.Monad.Trans.Free re-exports `FreeF`

and `FreeT`

module Control.Monad.Trans.Class

module Control.Monad.Trans.Free

module Pipes