| > | Also, is there a way to do something similar but for 'lazy' rather than | > | 'seq'? I want something of type | > | | > | type World__ = State# RealWorld | > | | > | {-# NOINLINE newWorld__ #-} | > | newWorld__ :: a -> World__ | > | newWorld__ x = realWord# -- ??? | > | | > | except that I need newWorld__ to be lazy in its first argument. I need | > | to convince the opimizer that the World__ newWorld__ is returning | > | depends on the argument passed to newWorld__. | > | > I don't understand what you meant here. The definition of newWorld__ that you give is, of course, | lazy in x. | | it is getting type 'Absent' assigned to it by the demand analysis, I | want it to be lazy (and not strict) Ah I think I understand now. You want a lazy primop discard# :: a -> () Now you can write newWorld x = discard x `seq` realWorld# The code generator treats (discard# x) as (), and (case (discard# x) of () -> e) as e. It should be a primop so that this behaviour is not exposed too early. An alternative would be to do the transformation in the core-to-STG step, but that might be too early. Still easier would be to write discard x = () {-# NOINLINE[0] discard #-} to prevent it getting inlined until the final stages of the optmisier. The trouble is that I have no idea of what it means to expose discard "too early" is in your case. Not hard to implement if you feel like doing so. Simon