| PrelBase contains the appended code. Am I correct in | assuming that the stuff is structured as it is, because the | "map" rule first `breaks' the map `open', which exposes it | to the various foldr/build rules, and if no foldr/build rule | matches, the "mapList" rule `closes' it again in a later | phase of optimisation - after build was inlined? If so, it | seems like the whole thing depends a bit on the timing of | the various optimsations (the map might be closed again | before any of the foldr/build rules fires). Is this maybe | the reason that build has an INLINE 2 pragma, which delays | its inlining, and thus, the closing of the map? That's exactly it. | All very cunning, it seems ;-) A bit too cunning for comfort. I wish I could think of a better way to expose map's impl using build without paying a price for doing so if it turns out not to fuse with anything. But so far I've failed to do so. Is this a propos of your new transformations for parallelism? Simon