[Haskell-cafe] unsafeInterleaveIO, lazyness and sharing

Hello, Haskell is non-strict but not necessarily lazy. So it’s possible that an expression is reduced to WHNF although it is not used yet. Could this “early reduction” also happen to outputs of unsafeInterleaveIO actions (which might trigger the action too early)? While I’d expect those outputs to be evaluated lazily (reduced as late as possible), I cannot find anything in the docs that guarantees this. In addition, I’d like to know whether unsafeInterleaveIO outputs are guaranteed to be evaluated at most once so that the “interleaved action” is executed at most once. Again, I suppose that this is the case while I cannot find a guarantee for it. Best wishes, Wolfgang