#11199: Outdated documentation for type operators -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Documentation | Version: 7.11 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- John Leo writes: According to sections 7.4.3 and 7.4.4 of the latest [https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/data- type-extensions.html GHC documentation] you can define (7.4.3) an infix type constructor as long as it begins with a colon, for example {{{ data a :*: b = Foo a b }}} and furthermore (7.4.4) you can define an infix operator without having to use a colon if you enable the `TypeOperators` extension: {{{ data a * b = Foo a b }}} However if I try the former without using `TypeOperators` I get this compiler error in 7.10.2: {{{ Illegal declaration of a type or class operator ‘:*:’ Use TypeOperators to declare operators in type and declarations }}} Using `TypeOperators` fixes this, but then `*` without colon also works so I don't see the point of using colon anymore. My guess is this was some some kind of historical distinction which is no longer valid and the documentation needs to be updated. Is this true, or am I missing something? ------------------------- Answer: it's just historical and the documentation is wrong. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11199 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler