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Outdated documentation for type operators

    • Closed Issue created by Richard Eisenberg @rae

    John Leo writes:

    According to sections 7.4.3 and 7.4.4 of the latest 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    My guess is this was some some kind of historical distinction which is no longer valid and the documentation needs to be updated.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.

    Trac metadata
    Trac field Value
    Version 7.11
    Type Bug
    TypeOfFailure OtherFailure
    Priority normal
    Resolution Unresolved
    Component Documentation
    Test case
    Differential revisions
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    Related
    Blocking
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    Operating system
    Architecture
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