Problem 1 -- you have to use define/generic if you want to use the generic version of something in the context of a set of specific method implementations. That's by design.
Problem 2 -- what error message or unexpected behavior are you getting? That should work, it sounds like a bug in define/generic if it's not working. Carl Eastlund On Fri, Aug 16, 2013 at 4:36 PM, J. Ian Johnson <i...@ccs.neu.edu> wrote: > I'm starting to use generics, and me being myself, I wrote some macros to > make writing method definitions easier. > But, I'm seeing that #:methods seems to rebind method identifiers in a way > that hygiene interferes with. > > I would expect to be allowed to do the following two things (problems > annotated): > > (struct exp (label fvs-box)) ;; parent struct for all expressions > (define-generics binds-variables > [free-box binds-variables] > [free binds-variables #:bound [bound]] > #:fallbacks [(define (free e #:bound [bound ∅]) ∅) > (define free-box exp-fvs-box)] > #:fast-defaults ([(compose unbox free-box) > (define (free e #:bound bound) (unbox (free-box > e)))])) ;; problem 1: free-box not in scope > > (define-syntax-rule (def-free e gfree bound struct [(pats ...) rhss ...]) > (begin > (define/generic gfree free) ;; problem 2: since #:methods rebinds > free, this is not in the scope one would expect with its definition in the > define-generics form. > (define (free e #:bound [bound ∅]) > (match e [(struct _ fvs-box pats ...) > (set-box! fvs-box > (let () rhss ...))])))) > > (struct var exp (name) #:transparent > #:methods gen:binds-variables > [(def-free e gfree bound var [(x) (if (x . ∈ . bound) ∅ (set > x))])]) > > I have workarounds thanks to stamourv, but they're unpleasant: > Problem 1: define free in fast-defaults as an eta-expansion of a > definition outside the define-generics form that does what you want. > Problem 2: add free as a parameter to def-free, and pass free in at all > uses of def-free. > > The first problem seems like more of a programming error than the use of > the wrong tool. > The second problem seems like generic method identifiers should be > syntax-parameters, if they indeed need to be rebound in the rhs of the > #:methods argument. > > Are these expectations unreasonable/against the design decisions for > generics? > Thanks, > -Ian > > _________________________ > Racket Developers list: > http://lists.racket-lang.org/dev >
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