Hi Eliot,
I agree with most things you say (except the conclusion :)), and I think that
we are talking about complementary issues.
As I mentioned before, there already is a need to distinguish between a plain
selector and one that is associated with pragmas. This is what you find in
PragmaType in Spotter and Inspector. This is a kind of meta-object and having
it adds value. I can search for pragmas “type” (we can also call it a
PragmaSelector), and I can distinguish between all occurrences of a pragma
“type” and its utilization in computation. But, the current implementation of
PragmaType is a mere pseudo-meta-object, given that it has no casual connection
to the runtime.
What we know from Smalltalk is that the analysis model does not have to differ
from the runtime one. The consequence is that every time we do see a
difference, we should investigate because we might uncover a hidden need
opportunity.
I know the VW model, and indeed, we could have something like:
MyConcept class>>myPragmaDefinition
“a comment about the pragma"
<pragma: #selector>
However, this only deals with the definition of the pragma type not with the
internal representation. There could still well be an object that encapsulates
both the selector and the comment. And that object would also allow us to build
tools around it. We could call it a PragmaType, PragmaDefinition, or even
PragmaSelector. And we could get the Pragma to point to this type either
through an inst var or through a query (I would probably prefer an instvar).
I think that this proposition does not remove from the simplicity of the
implementation at all, but allows the new needs to be accommodated nicely. The
alternative is to not do anything, in which case we will continue to have an
analysis-only-pseudo-meta-object which is not nice at all. I do not think we
should jump on this lightly, but I do think we should have a critical look and
evaluate the options.
What do you think?
Cheers,
Doru
> On Jun 27, 2016, at 2:39 PM, Eliot Miranda <eliot.mira...@gmail.com> wrote:
>
> Hi Doru,
>
>> On Jun 27, 2016, at 3:52 AM, Tudor Girba <tu...@tudorgirba.com> wrote:
>>
>> Hi,
>>
>> The CompiledMethod already has a way to retrieve Pragma instances:
>>
>> CompiledMethod>>pragmas.
>>
>> However, the Pragma instance does not have a meta-object associated with it.
>> So, I would first start from adding that one and linking such a PragmaType
>> to its instances. The important thing here would be that all Pragma
>> instances with a certain selector should reference the same PragmaType.
>
> Let me express a dissenting opinion. Our pragma system is minimal yet
> powerful. By using Message instances (with literal arguments) to represent
> pragmas we get
> - executable pragmas that can be applied using perform: or wrappers such as
> sentTo:
> - we can use conventional browsing queries (implementors and senders) to
> discover which methods are marked by a specific pragma and what
> pragma-processing tools implement a specific pragma.
> - a rich pragma language that can have many, named parameters
> - a system which doesn't need its own language, but reuses the existing
> Smalltalk parsing facilities, and so is easier to learn and to implement
>
> So its parsimony is an important part of its virtues. It is minimal.
>
> One thing missing from the Squeak/Pharo implementation is the set of legal
> pragmas a class accepts. In VisualWorks a class implements the <pragma:
> #pragma:selector:> (it might be <pragmas: #(pragma:selector:one:
> pragma:selector:two:)>) to define the legal set of pragmas. [Implementation
> note, these are /not/ searched for ahead of compilation; instead, the parser
> delays searching for class-side methods containing pragma: pragmas until it
> encounters a pragma, and it searches for all class side methods, including in
> superclasses).
>
> This scheme allows pragmas to be checked; only pragmas in the set of allowed
> pragmas are accepted, and it allows collision-free extensibility; any package
> can add a set of legal pragmas to a class merely by choosing a method
> selector that won't collide with any other containing pragma: pragmas, eg
> kernelPragmas
> <pragma: #primitive:>
> <pragma: #primitive:error:>
> <pragma: #primitive:module:>
> <pragma: #primitive:module:error:>
>
> We're missing this, which means our compilers don't safely check for valid
> pragmas and can't reject invalid or unrecognized ones, which is error prone.
>
> If we implemented this then we would have a natural place to comment pragmas
> in the method that defines a particular pragma, one that would be found using
> senders.
>
> None of this requires a meta object. It is perfectly recursive; using itself
> to implement itself. I find this very elegant (I didn't invent pragma:
> pragmas; Steve Dahl did, and it's a cool idea).
>
> So as an inventor of pragmas I'd like to ask for the minimal implementation
> outlined above. I'd like that we didn't j tricycle a specific meta object,
> with all the additional tools that implies, and instead stick to the
> minimalist and parsimony of the original design and use pragmas to comment
> pragmas.
>
>> Cheers,
>> Doru
>
> Thanks for reading.
> Cheers, Eliot
>
>>> On Jun 27, 2016, at 12:34 PM, Denis Kudriashov <dionisi...@gmail.com> wrote:
>>>
>>>
>>> 2016-06-27 12:12 GMT+02:00 Tudor Girba <tu...@tudorgirba.com>:
>>> Hi,
>>>
>>> That is my proposal as well: introduce a first class entity that describes
>>> a Pragma instance. Who would be interested to play with this?
>>>
>>> How it could be done?
>>> Probably compiler could search preferred Pragma class for given selector.
>>> And then we will have collection of real pragma instances inside
>>> CompiledMethod. What do you think?
>>
>> --
>> www.tudorgirba.com
>> www.feenk.com
>>
>> "Be rather willing to give than demanding to get."
>>
>>
>>
>>
>>
>
--
www.tudorgirba.com
www.feenk.com
"When people care, great things can happen."
