Re: Proposal: Add a strict version of <$> for monads

Obvious +1. On Fri, Nov 29, 2013 at 1:07 PM, Johan Tibell wrote:

Hi all,

I propose we add a strict version of <$> to base:

-- | A strict version of 'Data.Functor.<$>' for monads. (<$!>) :: Monad m => (a -> b) -> m a -> m b f <$!> m = do a <- m return $! f a {-# INLINE (<$!>) #-}

infixl 4 <$!>

It works on Monads instead of Functors as required by us inspecting the argument.

This version is highly convenient if you want to work with functors/applicatives in e.g. parser and avoid spurious thunks at the same time. I realized that it was needed while fixing large space usage (but not space-leak) issues in cassava.

I believe Edward Kmett discovered the need for it independently as well.

Deadline: 3 weeks

Cheers, Johan

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