[racket] JSExprs and hashtables

Or come to think of it would generalizing value types like (-val ‘null) in this case to for instance Symbol also fix cases like this?

On Jan 19, 2015, at 10:09 AM, Alexander D. Knauth <alexander at knauth.org> wrote:

> If there was a way to convert a “value” type to a more general type, for instance convert all hash-table value types to HashTableTop, or vector value types to VectorTop, etc. and then use (not (or (subtype t1 t2) (subtype t2 t1))) or something like that, could that catch cases like this?
> 
> On Jan 19, 2015, at 9:58 AM, Sam Tobin-Hochstadt <samth at cs.indiana.edu> wrote:
> 
>> 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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> 
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