Re[2]: [Haskell-cafe] matrix computations based on the GSL

On Mon, 18 Jul 2005, Bulat Ziganshin wrote:

GHC also have a RULES pragma which can be used to automatically convert, for example, "mmap (*)" to "multipleElementWise".

Nice idea! But how can GHC decide which optimization is better? M.map sin . M.map cos can be optimized to M.map (sin . cos) or M.sin . M.cos Which is better?