Add operator <%>, or similar, as <%> = flip fmap
|Reported by:||bunimo||Owned by:|
|Type of failure:||None/Unknown||Test Case:|
|Related Tickets:||Differential Rev(s):|
Often, piping results through one function after another provides a good conceptual flow to the code. But when the functions are a mixture of monadic and pure, it can seem more convoluted than it actually is. For example, compare:
do a <- monadicResult let b = pureFunction2 . pureFunction 1 <$> a c <- monadicFunction1 b >>= monadicFunction2
c <- monadicFunction2 =<< monadicFunction1 =<< pureFunction2 <$> pureFunction1 <$> monadicResult
But this reading from bottom-to-up seems backwards, especially considering monadic code is more traditionally top-to-bottom, left-to-right.
I'd like to propose adding a new operator
infixl 1 <%> (<%>) :: Functor f => f a -> (a -> b) -> f b (<%>) = flip fmap
so that the following can be written. It is obvious what the intent of the code is. There are no unnecessary temporary variables. It conforms to typical monadic code direction. It is visually pleasing.
c <- monadicResult <%> pureFunction1 <%> pureFunction2 >>= monadicFunction1 >>= monadicFunction2