Re: [Haskell] Re: Using implicit parameter constraints in data decl

8 Nov 2004

      Benjamin Franksen wrote:
...
On Sunday 07 November 2004 23:19, Ben Rudiak-Gould wrote:
...
Does this do what you want?:
data Test = Test { name :: (?val::Bool) => String }
Thanks for the hint, but no:
TestBug.hs:4:
   Illegal constraint ?val :: Bool
   In the type: ({?val :: Bool} => String) -> Test
   While checking the type of constructor `Test'
   In the data type declaration for `Test'
Try using -fglasgow-exts instead of -fimplicit-params. Without 
glasgow-exts you can't use nested contexts in any circumstances; e.g. 
you can't write

    test :: ((?val::Bool) => String) -> ()

which is (similar to) the type that the data constructor Test needs to have.

-- Ben