#9545: Evaluate Takano Akio's foldrW/buildW fusion framework as a possible replacement for foldr/build -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: task | Status: new Priority: normal | Milestone: Component: | Version: 7.9 libraries/base | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Project (more Unknown/Multiple | than a week) Type of failure: | Blocked By: None/Unknown | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by dfeuer): === Update === Takano Akio's draft implementation has one or a few saturation issues and missing pragmas that prevent some necessary inlining when the fusion pipeline is not "capped" with a `foldrW`. This seems easy to fix, and I have done so for `map`. Dan Doel recognized that `foldrW/buildW` fusion, applied to situations currently handled with `foldr/build`, tends to produce recursive forms that pass a static argument around and around without touching it. He discovered that a modified version of `buildW`, call it `buildWForgetful` for now, can be used instead of `buildW` when recursion defining the builder satisfies a simple condition common to many important examples. One serious difficulty in dealing with this framework is the difficulty of ''understanding'' it. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9545#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler