#10121: operational semantics is incomplete? -------------------------------------+------------------------------------- Reporter: javran | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: | Version: 7.8.4 Documentation | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- I was trying to read `docs/core-spec/core-spec.pdf` to understand the operational semantics for core language. So I started off by playing with operational semantics rules manually. But I found the following expression gets stuck: {{{#!hs v1 = let fix = \f -> let x = f x in x pf = \f x -> if x == 0 then x else f (pred x) in (fix pf) 2 -- S_LETNONREC v2 = ((\f -> let x = f x in x) (\f x -> if x == 0 then x else f (pred x))) 2 -- S_APP v3 = (let x = (\f x -> if x == 0 then x else f (pred x)) x in x) 2 -- S_APP; S_LETREC v4 = (let x = (\f x -> if x == 0 then x else f (pred x)) x in (\f x -> if x == 0 then x else f (pred x)) x) 2 -- S_APP v5 = (let x = (\f x -> if x == 0 then x else f (pred x)) x in (\x1 -> if x1 == 0 then x1 else x (pred x1))) 2 }}} at this point `x` is not a free variable so `S_LETRECRETURN` cannot be applied. Did I make it wrong or some rules are missing for the operational semantics? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10121 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler