[racket] [typed racket] typing monads

From: Ryan Culpepper (ryan at cs.utah.edu)
Date: Thu Oct 20 15:35:24 EDT 2011

On 10/20/2011 01:27 PM, Jay McCarthy wrote:
> On Thu, Oct 20, 2011 at 12:52 PM, Eric Tanter<etanter at dcc.uchile.cl>  wrote:
>> Thanks Sam,
>> Actually, that's not what we're after.
>> In untyped Racket, we have a struct monad:
>> (struct monad
>>   (;; A ->  M A
>>    return
>>    ;; A ->  (A ->  M B) ->  M B
>>    bind))
>> Then we have several instantiations (exception, state, what-have-you):
>> (define my-fancy-monad (monad (lambda ...) (lambda ...)))
> How do you protect against combing the Maybe monad's bind with the
> State monad's bind? Monads are more like objects where the methods
> have to take the same kind of thing, not just some higher level monad
> class.

I expect that's what the M type constructor is for.

It looks like Eric's monad struct is just a reification of the Haskell 
type class dictionary for a monad instance (type).

Eric, is your question whether Typed Racket can parameterize a typed 
structure of a type constructor rather than a type?


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