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overPost #116

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55a2413
overPost
BebeSparkelSparkel Jul 14, 2020
df70386
reordered
BebeSparkelSparkel Jul 14, 2020
ef0b86e
imports
BebeSparkelSparkel Jul 14, 2020
2819e0b
export
BebeSparkelSparkel Jul 14, 2020
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23 changes: 20 additions & 3 deletions src/Data/Lens/Setter.purs
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
-- | This module defines functions for working with setters.
module Data.Lens.Setter
( (%~), over, iover
, (<%~), overPost
, (.~), set
, (+~), addOver
, (-~), subOver
Expand All @@ -13,6 +14,7 @@ module Data.Lens.Setter
, (?~), setJust
, (.=), assign
, (%=), modifying
, (<%=), modifyingLensPost
, (+=), addModifying
, (*=), mulModifying
, (-=), subModifying
Expand All @@ -27,13 +29,15 @@ module Data.Lens.Setter

import Prelude

import Control.Monad.State.Class (class MonadState, modify)
import Control.Monad.State.Class (class MonadState, modify, get, put)

import Data.Lens.Types (IndexedSetter, Indexed(..), Setter, Setter')
import Data.Lens.Getter ((^.), to)
import Data.Lens.Types (IndexedSetter, Indexed(..), Setter, Setter', Lens, Lens')
import Data.Maybe (Maybe(..))
import Data.Tuple (uncurry)
import Data.Tuple (Tuple(Tuple), uncurry)

infixr 4 over as %~
infixr 4 overPost as <%~
infixr 4 set as .~
infixr 4 addOver as +~
infixr 4 subOver as -~
Expand All @@ -47,6 +51,7 @@ infixr 4 setJust as ?~

infix 4 assign as .=
infix 4 modifying as %=
infix 4 modifyingLensPost as <%=
infix 4 addModifying as +=
infix 4 mulModifying as *=
infix 4 subModifying as -=
Expand All @@ -61,6 +66,11 @@ infix 4 assignJust as ?=
over :: forall s t a b. Setter s t a b -> (a -> b) -> s -> t
over l = l

overPost :: forall s t a b. Lens s t a b -> (a -> b) -> s -> Tuple b t
overPost l f x = Tuple y (x # l .~ y)
where
y = x ^. l <<< to f

-- | Apply a function to the foci of a `Setter` that may vary with the index.
iover :: forall i s t a b. IndexedSetter i s t a b -> (i -> a -> b) -> s -> t
iover l f = l (Indexed $ uncurry f)
Expand Down Expand Up @@ -103,6 +113,13 @@ assign p b = void (modify (set p b))
modifying :: forall s a b m. MonadState s m => Setter s s a b -> (a -> b) -> m Unit
modifying p f = void (modify (over p f))

modifyingLensPost :: forall s a m. MonadState s m => Lens' s a -> (a -> a) -> m a
modifyingLensPost l f = do
s <- get
let Tuple x s' = s # l <%~ f
put s'
pure x

addModifying :: forall s a m. MonadState s m => Semiring a => Setter' s a -> a -> m Unit
addModifying p = modifying p <<< add

Expand Down