On Mon, May 07, 2007 at 06:57:51PM -0400, Isaac Dupree wrote:
Malcolm Wallace wrote:
But I guess this semantics accords with Isaac's suggested definition: evaluate x = (x `seq` return x) >>= return
Let's try a little Equational Reasoning: evaluate x = (x `seq` return x) >>= return evaluate x = (>>=) (seq x (return x)) return evaluate x = bindIO (seq x (returnIO x)) returnIO evaluate x = IO (\st1 -> case unIO (seq x (returnIO x)) st1 of (# st2, a #) -> unIO (returnIO a) st2) evaluate x = IO (\st1 -> case unIO (seq x (returnIO x)) st1 of (# st2, a #) -> (# st2, a #)) evaluate x = IO (\st1 -> case seq x (\st3 -> (# st3, x #)) st1 of (# st2, a #) -> (# st2, a #)) evaluate x = IO (\st1 -> case (case x of __DEFAULT -> (\st3 -> (# st3, x #))) st1 of (# st2, a #) -> (# st2, a #)) evaluate x = IO (\st1 -> case x of __DEFAULT -> case (\st3 -> (# st3, x #)) st1 of (# st2, a #) -> (# st2, a #)) evaluate x = IO (\st1 -> case x of __DEFAULT -> case (# st1, x #) of (# st2, a #) -> (# st2, a #)) evaluate x = IO (\st1 -> case x of __DEFAULT -> (# st1, x #)) evaluate x = IO (\st1 -> case x `seq` () of () -> (# st1, x #)) evaluate x = GHC.Exception.evaluate x Stefan