Add apWhen

Author: kleinreact

clash-prelude/src/Clash/Explicit/Signal.hs

@@ -3,7 +3,7 @@ Copyright  :  (C) 2013-2016, University of Twente,
                   2016-2019, Myrtle Software,
                   2017-2022, Google Inc.
                   2020     , Ben Gamari,
-                  2021-2024, QBayLogic B.V.
+                  2021-2025, QBayLogic B.V.
 License    :  BSD2 (see the file LICENSE)
 Maintainer :  QBayLogic B.V. <devops@qbaylogic.com>
 
@@ -238,6 +238,7 @@ module Clash.Explicit.Signal
   , regMaybe
   , regEn
   , mux
+  , apWhen
     -- * Simulation and testbench functions
   , clockGen
   , resetGen

clash-prelude/src/Clash/Signal.hs

@@ -2,7 +2,7 @@
 Copyright  :  (C) 2013-2016, University of Twente,
                   2016-2019, Myrtle Software Ltd,
                   2017     , Google Inc.,
-                  2021-2024, QBayLogic B.V.
+                  2021-2025, QBayLogic B.V.
 License    :  BSD2 (see the file LICENSE)
 Maintainer :  QBayLogic B.V. <devops@qbaylogic.com>
 
@@ -202,6 +202,7 @@ module Clash.Signal
   , regMaybe
   , regEn
   , mux
+  , apWhen
     -- * Simulation and testbench functions
   , clockGen
   , resetGen

clash-prelude/src/Clash/Signal/Internal.hs

@@ -126,6 +126,7 @@ module Clash.Signal.Internal
   , syncRegister#
   , registerPowerup#
   , mux
+  , apWhen
     -- * Simulation and testbench functions
   , clockGen
   , tbClockGen
@@ -1653,6 +1654,13 @@ mux :: Applicative f => f Bool -> f a -> f a -> f a
 mux = liftA3 (\b t f -> if b then t else f)
 {-# INLINE mux #-}
 
+-- | Updates a value inside an 'Applicative' context if and only if
+-- the given Boolean condition evaluates to 'True' in the same
+-- context.
+apWhen :: Applicative f => f Bool -> (a -> a) -> f a -> f a
+apWhen cond upd x = mux cond (upd <$> x) x
+{-# INLINE apWhen #-}
+
 infix 4 .==.
 -- | The above type is a generalization for:
 --