This has bothered me too, but I've realized that I was on the wrong track. The string "a" and symbol 'b are not different types. A struct (Foo "a" 'b), or (list "a" 'b), is a homogeneous data structure of type (U String Symbol) just like Alexander said. This really upsets me -- I like the Hindley Milner world where the compiler warns me if I make a list [1, "two"] and forces me to wrap the int and string into a new datatype. But Typed Racket is not HM.
About the proposal, I'm confused about what the syntax in Section 2.1 should do -- what is a "first class member of Typed Racket's type system"? - Should an A only be a base type like String or Symbol - Do you mean to infer the type of the first thing put into the struct as the exact type for everything else? - Would "first class members" prevent me from filling a struct with members of (define-type (Option A) (U 'None (Some A))), where "Some" is a struct with one field? I totally agree that "something needs fixing", but I'm not sure what. On Thu, Jan 29, 2015 at 10:13 PM, Alexis King <lexi.lam...@gmail.com> wrote: > Or Any for that matter. I know. The fact that it could be literally > anything was sort of the point. > > On Jan 29, 2015, at 19:10, Alexander D. Knauth <alexan...@knauth.org> > wrote: > > Um, for this: > (module > <http://docs.racket-lang.org/reference/module.html#%28form._%28%28quote._~23~25kernel%29._module%29%29> > typed typed/racket/base (provide > <http://docs.racket-lang.org/reference/require.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._provide%29%29> > (struct-out > <http://docs.racket-lang.org/reference/require.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._struct-out%29%29> > Foo)) (struct > <http://docs.racket-lang.org/ts-reference/special-forms.html#%28form._%28%28lib._typed-racket%2Fbase-env%2Fprims..rkt%29._struct%29%29> > [A] Foo ([x : > <http://docs.racket-lang.org/ts-reference/special-forms.html#%28form._%28%28lib._typed-racket%2Fbase-env%2Fprims..rkt%29._~3a%29%29> > A] [y : > <http://docs.racket-lang.org/ts-reference/special-forms.html#%28form._%28%28lib._typed-racket%2Fbase-env%2Fprims..rkt%29._~3a%29%29> > A]) #:transparent)) > > (Foo "a" 'b) > Should be fine because Foo could be instantiated at the type (U String > Symbol). > > On Jan 29, 2015, at 9:25 PM, Alexis King <lexi.lam...@gmail.com> wrote: > > I recently ran into a problem in which opaque types (types imported from > untyped code) cannot by parameterized by Typed Racket. I initially > encountered this problem in my attempt to port 2htdp/image to TR > <https://github.com/lexi-lambda/racket-2htdp-typed/issues/1>. > > After some further consideration, I’m interested in adding support to make > something like this possible, which would certainly have additional > benefits beyond this specific use-case. I’ve outlined my proposal here: > http://lexi-lambda.github.io/racket-parametric-opaque-types/ > > Any feedback, suggestions, or advice would be appreciated, especially from > those who are familiar with Typed Racket’s internals. > > Thank you, > Alexis > _________________________ > Racket Developers list: > http://lists.racket-lang.org/dev > > > > > _________________________ > Racket Developers list: > http://lists.racket-lang.org/dev > >
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