[racket] JSExprs and hashtables

On Mon, Jan 19, 2015 at 9:54 AM, Alexander D. Knauth
<alexander at knauth.org> wrote:
> Would there be a more general solution that wouldn’t be specific to just hash-tables?

I'm not sure what you mean. The code you suggested fixes a
hash-table-specific limitation in Typed Racket. If the question is
could `overlap` not have so many cases, then I'd certainly like that,
but it's very hard to accomplish. In particular, abstractions like
`Sequence` and `Evt` overlap with arbitrarily many types. A more
principles treatment of such abstractions would help, but we don't yet
know how to do that.

Sam

>
> On Jan 19, 2015, at 9:38 AM, Sam Tobin-Hochstadt <samth at cs.indiana.edu> wrote:
>
>> This is a correct improvement to Typed Racket -- I'll make it shortly.
>>
>> Sam
>>
>> On Mon, Jan 19, 2015 at 8:41 AM, Alexander D. Knauth
>> <alexander at knauth.org> wrote:
>>> I managed to fix this for your example by inserting these 3 lines into
>>> typed-racket/types/remove-intersect.rkt after line 67:
>>>         [(list-no-order (Value: (not (? hash?)))
>>>                         (or (? Hashtable?) (? HashtableTop?)))
>>>          #f]
>>> There is probably a better solution though.
>>>
>>> On Jan 19, 2015, at 7:36 AM, Alexander D. Knauth <alexander at knauth.org>
>>> wrote:
>>>
>>> Since hash-tables can be mutable as far as TR knows, (HashTable Symbol
>>> String) is not a subtype of (HashTable Symbol JSExpr).
>>> To work around this, you can do this:
>>> #lang typed/racket/base
>>> (require typed/json)
>>> (: jsx JSExpr)       ; <-- jsx is what I ultimately want.
>>> (define jsx (ann #hasheq((a . "val1") (b . "val2") (c . "val3")) (HashTable
>>> Symbol JSExpr)))
>>>
>>> Or this would work too:
>>> #lang typed/racket/base
>>> (require typed/json)
>>> (: jsx (HashTable Symbol JSExpr))       ; <-- jsx is what I ultimately want.
>>> (define jsx #hasheq((a . "val1") (b . "val2") (c . "val3")))
>>>
>>> Or you could use (inst make-immutable-hasheq Symbol JSExpr) instead of using
>>> #hasheq, and it would do the same thing.
>>>
>>>
>>> On Jan 19, 2015, at 1:28 AM, Jordan Johnson <jmj at fellowhuman.com> wrote:
>>>
>>> Hi all,
>>>
>>> I’ve been trying to create JSExprs, as defined in the typed/json library.
>>> This is one of those instances where it seems like I must be making things
>>> harder than they should be, but I’m still feeling like a duck on
>>> rollerskates in TR, so I want to make sure I’m not missing an easier way to
>>> do it.
>>>
>>> Would you please confirm if this is indeed a smallest-possible solution?
>>>
>>> ;;;; begin
>>> #lang typed/racket/base
>>>
>>> (require typed/json)
>>>
>>> (: jsx JSExpr)       ; <-- jsx is what I ultimately want.
>>>
>>> ;; Attempt #1:
>>> #;
>>> (define jsx #hasheq((a . "val1") (b . "val2") (c . "val3")))
>>>
>>> #| Resulting error:
>>> Type Checker: type mismatch
>>>  expected: JSExpr
>>>  given: (HashTable Symbol String)
>>>
>>> [This seems weird, since it seems like (HashTable Symbol String) should be
>>> a subtype of JSExpr. Is the problem that the typechecker can’t recognize
>>> the Strings as JSExprs?]
>>> |#
>>>
>>> ;; Attempt #N (shortest successful version I’ve found):
>>> (define jsx
>>>  (for/hasheq : (HashTable Symbol JSExpr) ([k '(a b c)]
>>>                                           [v '("val1" "val2" "val3")])
>>>    (values k v)))
>>> ;;;; end
>>>
>>> Regards,
>>> Jordan
>>>
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>