when is:exact

when :: Applicative f => Bool -> f () -> f ()
base Control.Monad GHC.Base, haskell-gi-base Data.GI.Base.ShortPrelude, relude Relude.Bool.Reexport, ghc-internal GHC.Internal.Base GHC.Internal.Control.Monad, verset Verset
Conditional execution of Applicative expressions. For example,

Examples

when debug (putStrLn "Debugging")
will output the string Debugging if the Boolean value debug is True, and otherwise do nothing. 
>>> putStr "pi:" >> when False (print 3.14159)
pi:
when :: Applicative f => Bool -> f () -> f ()
base-compat Control.Monad.Compat, protolude Protolude.Monad, rio RIO.Prelude, base-prelude BasePrelude, turtle Turtle, shelly Shelly Shelly.Lifted Shelly.Pipe, classy-prelude ClassyPrelude, Cabal-syntax Distribution.Compat.Prelude, universum Universum.Bool.Reexport, ihaskell IHaskellPrelude, basement Basement.Compat.Base Basement.Imports, base-compat-batteries Control.Monad.Compat, Agda Agda.Utils.Monad, rebase Rebase.Prelude, persistent-test Init, massiv-test Test.Massiv.Utils, incipit-base Incipit.Base, LambdaHack Game.LambdaHack.Core.Prelude, cabal-install-solver Distribution.Solver.Compat.Prelude, faktory Faktory.Prelude, can-i-haz Control.Monad.Except.CoHas Control.Monad.Reader.Has, vcr Imports, yesod-paginator Yesod.Paginator.Prelude, control-monad-free Control.Monad.Free, distribution-opensuse OpenSuse.Prelude, termonad Termonad.Prelude
Conditional execution of Applicative expressions. For example, 
when debug (putStrLn "Debugging")
will output the string Debugging if the Boolean value debug is True, and otherwise do nothing.
when :: Monoid m => Bool -> m -> m
utility-ht Data.Monoid.HT
\b m -> when b m == mfilter (const b) (m::Maybe Ordering)

\b m -> when b m == mfilter (const b) (m::String)
when :: ArrowIf a => a b b -> a b c -> a b b
hxt Control.Arrow.ArrowIf
f `when` g : when the predicate g holds, f is applied, else the identity filter this
when :: CFilter i -> CFilter i -> CFilter i
HaXml Text.XML.HaXml.Combinators
Interior editing: f when g applies f only when the predicate g succeeds, otherwise the content is unchanged.
when :: (ToBool bool, Monad m) => bool -> m () -> m ()
cond Control.Conditional
Generalization of when
when :: (Monoid e) => (a -> Bool) -> Wire s e m a a
netwire Control.Wire.Interval
When the given predicate is true for the input signal.
  • Depends: now.
  • Inhibits: when the predicate is false.
when :: (Monad m k, PreArrow k, u ~ UnitObject k, ObjectPair k (m u) u) => Bool -> m u `k` m u
constrained-categories Control.Category.Constrained.Prelude Control.Monad.Constrained
when :: (Int -> Bool) -> (Pattern a -> Pattern a) -> Pattern a -> Pattern a
tidal Sound.Tidal.Boot, tidal-core Sound.Tidal.Core
The given pattern transformation is applied only when the given test function returns True. The test function will be called with the current cycle as a number. 
d1 $ when (elem '4' . show)
(striate 4)
$ sound "hh hc"
The above will only apply striate 4 to the pattern if the current cycle number contains the number 4. So the fourth cycle will be striated and the fourteenth and so on. Expect lots of striates after cycle number 399.
when :: Monoid m => Bool -> m -> m
BNFC BNFC.Utils
Generalization of when.
when :: Bool -> Cont r () -> Cont r ()
control-dsl Control.Dsl Control.Dsl.Cont
when :: RBool -> RSet a -> RSet a
rec-def Data.Recursive.Set
An kind of if-then-else statement. Because of monotonicity requirements, this should be sufficient. 
RS.get (RS.when b r) === (if RB.get b then RS.get r else S.empty)