Simon, Richard, others,
I'm making progress on this one but before going too far I want to get a green light on my design proposal (points 1-3). I've also bumped into some
#6018: Injective type families -------------------------------------+------------------------------------- Reporter: lunaris | Owner: jstolarek Type: feature | Status: new request | Milestone: 7.10.1 Priority: normal | Version: 7.4.1 Component: Compiler | Keywords: TypeFamilies, Resolution: | Injective Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Difficulty: Unknown Type of failure: | Blocked By: None/Unknown | Related Tickets: #4259 Test Case: | Blocking: | Differential Revisions: Phab:D202 | -------------------------------------+------------------------------------- Comment (by heisenbug): Replying to [comment:73 jstolarek]: problems and have a couple of questions.
Just a side question. I have a type level Map: {{{ type family Map (f :: k -> l) (ks :: [k]) :: [l] where ... }}} When I declare this as injective (presumably) with {{{ type family Map (f :: k -> l) (ks :: [k]) = result :: [l] | result -> ks where ... }}} then `f` must be injective for this to work. Concretely, will this invocation be considered injective by GHC (`:set -XDataKinds`) ? {{{ Map IO '[Int, (), Bool] }}} Thanks, Gabor -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/6018#comment:74 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler