On Nov 2, 2007, at 6:35 , apfelmus wrote:
during function evaluation. Then, we'd need a "purity lemma" that states that any function not involving the type *World as in- and output is indeed pure, which may be a bit tricky to prove in the presence of higher-order functions and polymorphism. I mean, the function arrows are "tagged" for side effects in a strange way, namely by looking like *World -> ... -> (*World, ...).
I don't quite see that; the Clean way looks rather suspiciously like my "unwrapped I/O in GHC" example from a couple weeks ago, so I have trouble seeing where any difficulty involving functions not using *World / RealWorld# creeps in. I will grant that hiding *World / RealWorld# inside IO is cleaner from a practical standpoint, though. Just not from a semantic one. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH