Problem

SML/NJ accepts curried functor parameter syntax, for example:

functor F(M: ORD_MAP) (S: ORD_SET) :>
sig
    val func: string list -> S.set M.map
end =
    (* ... *)
end

However, this triggers a parse error: expected '=' at the second parameter group (S : ...). It looks like Millet parses functor F (M : ...) and then expects = / : ... / :> ..., so the extra (S : ...) is rejected and causes cascading errors.

Solution

The curried functor parameter is the extention syntax in SML/NJ. It would be very helpful if Millet could support (or provide a mode for) this.