#10344: Make BranchList simpler -------------------------------------+------------------------------------- Reporter: goldfire | Owner: goldfire Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by goldfire): Replying to [comment:2 simonpj]:
Yes yes! Simple is good! Needs a comment to stress that in the `BranchedList` case the list may legitimately be empty.
But a `BranchList Branched` currently still can't be empty -- Adam's empty CTF patch uses the `Maybe (CoAxiom Branched)` approach to deal with empty CTFs. Consumers of `fromBranchList` assume they're getting a non-empty list. So, we could do {{{ data BranchList a br where OneBranch :: a -> BranchList a Unbranched ManyBranches :: a -> [a] -> BranchList a Branched -- requires at least one element }}} This is certainly simpler than the current story. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10344#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler