Not reliably, no. GHC's current CSE is rather opportunistic: we take the opportunity if it's presented in the form let x = e in let y = e in .... A proper CSE pass would be a nice, containable, project. Simon From: glasgow-haskell-users-bounces@haskell.org [mailto:glasgow-haskell-users-bounces@haskell.org] On Behalf Of Conal Elliott Sent: 29 March 2008 01:53 To: glasgow-haskell-users@haskell.org Subject: simple CSE? I'd like to know if it's possible to get GHC to perform some simple CSE for function-level programming. Here's a simple example: liftA2 (*) sin sin :: Double -> Double which inlines and simplifies to \ t -> sin t * sin t A more realistic, equivalent, example: let b = sin <$> id in liftA2 (*) b b Can GHC be nudged into computing 'sin t' once rather than twice? Thanks, - Conal