#14806: Officially sanction certain unsafeCoerce applications with unboxed unary tuples -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: 8.6.1 Component: Documentation | Version: 8.2.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj):
`unsafeCoerce :: (A -> B) -> A -> (# B #)`
The first version in particular would be very useful for reducing both
I think you are right that this is ok. But the reverse is not {{{ unsafeCoerce :: (A -> {# B #)) -> A -> B }}} because the argument function may return an unevaluated `B`, while the returned function is supposed to guaranteed to return an evaluated `B`. Tricky. source code and generated code size in libraries supporting both strict and lazy operations. Would you care to explain your use-case? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14806#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler