#10708: Rejection of constant functions defined using conditional pattern matching -------------------------------------+------------------------------------- Reporter: HubertGaravel | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Resolution: invalid | Keywords: Operating System: Linux | Architecture: x86 Type of failure: GHC rejects | Test Case: valid program | Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by HubertGaravel): Thanks for the insight. If I try to reformulate, the definition of d3 is allowed by the syntax but forbidden by the static semantics. Perhaps the static semantics rule is too rigid and could be relaxed to make Haskell more regular. The example below shows that regularity is broken for arity 0 (empty pattern list). But I can live with this bizarre exception and will modify my Haskell generator to handle this corner case. Thanks again! Hubert {{{#!hs -- valid for arity 2 f2 x y | x == 0 = x f2 x y | x /= 0 = x + 1 -- valid for arity 1 f1 x | x == 0 = x f1 x | x /= 0 = x + 1 -- invalid for arity 0 f0 | 0 == 0 = 0 f0 | 0 /= 0 = 1 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10708#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler