Ah. Yes, that makes more sense. Thanks.
On Sat, Dec 9, 2017 at 3:32 PM, Robby Findler
> One hopefully helpful piece of information is that _all_ values in Racket
> are structs. So this predicate is telling you that this kind of value is
> revealing its inherent "structness" to you or not.
> In this case, the struct isn't transparent so it isn't revealing it. (Just
> like cons pairs don't reveal their structs, neither do rational numbers or
> procedures, etc.)
> Hopefully this helps the docs make more sense.
> On Sat, Dec 9, 2017 at 2:27 PM David Storrs <david.sto...@gmail.com> wrote:
>> (struct fruit (name color))
>> -> (struct? (fruit 'apple 'red))
>> This surprised me. I'm trying to wrap my head around the docs for
>> struct? and struct-info? and not having a lot of success. Is there a
>> way to simply say "is this a struct of some sort?"
>> I'm playing around with structs that contain information about structs
>> and I'd like to be able to validate the information that's going in:
>> (struct field-info (field-name predicate getter setter required?
>> default on-update)
>> #:guard (lambda (field-name predicate getter setter required?
>> default on-update type)
>> (define/contract (init-field-info field-name predicate
>> getter setter required? default on-update)
>> (-> symbol? ; field name
>> (-> any/c boolean?) ; predicate
>> (-> struct? any/c) ; getter
>> (-> struct? struct?) ; setter
>> boolean? ; required
>> (or/c (not/c procedure?) ; default
>> (-> struct? any/c))
>> (-> struct? any/c any) ; on-update
>> any ; unchecked return value
>> (when (and required? (not-equal? default
>> (raise-arguments-error 'init-field-info
>> "Cannot specify a default for a
>> required field"
>> "default" default))
>> (values field-name predicate getter setter required?
>> default on-update))
>> (init-field-info field-name predicate getter setter
>> required? default on-update)))
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