Per Larsson wrote:

I often use local loops in monadic code, e.g.

main = do ... let loop = do ... if cond then loop else return () loop

It seems that I can encode this idiom slightly more concise with the 'fix' operator (from Control.Monad.Fix), i.e.

main = do ... fix (\loop -> do ... if ...)

But is it really semantically equivalent? Is it as efficient?

Per

It is semantically equivalent. I don't know if it is as efficient; looking at the source code, I would expect GHC to inline fix anywhere it occurs, which yields your original version. Jonathan Cast