when package:haskell-gi-base

when :: Applicative f => Bool -> f () -> f ()
haskell-gi-base Data.GI.Base.ShortPrelude
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:
whenJust :: Monad m => Maybe a -> (a -> m ()) -> m ()
haskell-gi-base Data.GI.Base.Utils
When the given value is of "Just a" form, execute the given action, otherwise do nothing.