I wonder if something like this could bring it closer to being possible?: https://github.com/plt/racket/pull/564
On Mar 4, 2015, at 3:18 AM, Alexis King <[email protected]> wrote: > Disclaimer: this question is both a real question and me trying to push the > type system to its limits, so I’m not really expecting to get a satisfactory > answer. > > I posted a question on Stack Overflow here, but I’m guessing that this is > unfortunately far too localized to be answered there, so I’m posting it here > as well. The original question is as follows: > > I can write a simple function in untyped Racket called curry-all that takes a > list of functions, all of which accept the same kind of value for their first > argument, and produces a list of functions with their first arguments curried. > > (define (curry-all fs arg) > (map (λ (f) (curry f arg)) fs)) > For a running example of the above function, see this snippet on pasterack. > > This is a valid function, but I'm not sure if it's even possible to type in > Typed Racket given its polymorphic typing constructs. The type of curry > itself is already fairly complex, and obviously the type of curry-all would > need to be necessarily more complex. > > I made a relatively simple attempt at typing this function, though I was > quite aware that it would not function as I liked: > > (: curry-all > (All [a c b ...] > (Listof (-> a b ... b c)) a > -> (Listof (-> b ... b c)))) > (define (curry-all fs arg) > (map (λ ([f : (-> a b ... b c)]) > (curry f arg)) > fs)) > Obviously, this works if all the functions have identical types (which isn’t > worthless!), but it fails if they have different arities, even if their first > arguments’ types are shared. > > Is there any way to specify this function’s type so that it will work in a > more general case? > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users
____________________ Racket Users list: http://lists.racket-lang.org/users
