If you let the Simplifier have a crack at your code (i.e., compile with -O or better), the same code should be generated for the two defns of 'foo'. Try compiling with -ddump-simpl to verify. The first version is stricter, so it'll be preferable in -Onot mode. --sigbjorn Brian Hulley wrote:
Hi, I'm wondering if it is more efficient to pattern match against the components of a record instead of using the field functions, though I'd prefer to just use the field functions.
For example, if I write:
data R = R {_xRef :: !(IORef Int)}
foo :: Int -> R -> IO () foo i R{_xRef = xRef} = writeIORef xRef i
is the above more efficient than:
foo i r = writeIORef (_xRef r) i
I know this is probably a bit silly to worry about the overhead of an extra function call etc but I've at the moment got a lot of code using the first version and I think it would look much neater just using field labels but I don't want to modify it if it will be less efficient since speed is quite critical here.
Thanks, Brian.