On 21. 12. 20 18:14, George Neuner wrote:
>
> On 12/20/2020 3:34 PM, Dominik Pantůček wrote:
>> Hello Racketeers,
>>
>> there were some discussions about structs' introspection on the IRC
>> lately and one of the questions that arose was how to get field index
>> for arbitrary struct's arbitrary field.
>>
>> Not that it is possible... But the general discussion made me think
>> about why there are no unsafe variants for structs' accessors and
>> mutators.
>
> Have you looked at 'struct-field-info-list' and 'struct-field-index'?
>
> 'struct-field-index' works if you know the field name(s), and
> 'struct-field-info-list' returns fields defined by the struct type - so
> if your structs types are flat, you can make do with these.
>
> However, 'struct-field-info-list' returns only fields defined by the
> actual type and does not include fields that were inherited. What I
> don't see is any simple way to get at the struct's inheritance hierarchy
> - it seems that you have to iterate 'struct-type-info' to enumerate the
> supertypes.
>
> So it is "possible" (for some definition).
Yes, this approach would be useful to create the unsafe
accessors/mutators after the structs have been defined. Trouble is, one
would have to traverse the structs hierarchy and filter-out those
accessors/mutators, that are already defined by parent struct.
What I wanted to achieve was providing the unsafe variants
"transparently". Honestly, given enough time, the best solution for me
would be adding #:unsafe keyword to the struct form that would define
the unsafe variants.
My usage requires only struct-wide unsafe accessors. I implemented the
rest as an exercise to see what can be done (and to play with more
complex syntax-rules too).
It may be the case that using extract-struct-info and traversing the
structs' hierarchy during expansion phase might be more elegant solution
for implementing the whole unsafe-struct syntax. I will definitely look
into it more in the (relatively near) future.
Thank you,
Dominik
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