6.2.17. Local Fixity Declarations¶
A careful reading of the Haskell 98 Report reveals that fixity
infixr) are permitted to
appear inside local bindings such those introduced by
where. However, the Haskell Report does not specify the semantics of
such bindings very precisely.
In GHC, a fixity declaration may accompany a local binding:
let f = ... infixr 3 `f` in ...
and the fixity declaration applies wherever the binding is in scope. For
example, in a
let, it applies in the right-hand sides of other
let-bindings and the body of the
letC. Or, in recursive
expressions (The recursive do-notation), the local fixity
declarations of a
let statement scope over other statements in the
group, just as the bound name does.
Moreover, a local fixity declaration must accompany a local binding of that name: it is not possible to revise the fixity of name bound elsewhere, as in
let infixr 9 $ in ...
Because local fixity declarations are technically Haskell 98, no extension is necessary to enable them.