Having comments for pragma?

> On Jun 27, 2016, at 12:34 PM, Denis Kudriashov <[hidden email]> wrote:
>
>
> 2016-06-27 12:12 GMT+02:00 Tudor Girba <[hidden email]>:
> 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?

>> On Jun 27, 2016, at 12:34 PM, Denis Kudriashov <[hidden email]> wrote:
>>
>>
>> 2016-06-27 12:12 GMT+02:00 Tudor Girba <[hidden email]>:
>> 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."
>
>
>
>
>

> On Jun 27, 2016, at 2:39 PM, Eliot Miranda <[hidden email]> wrote:
>
> Hi Doru,
>
>> On Jun 27, 2016, at 3:52 AM, Tudor Girba <[hidden email]> 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 <[hidden email]> wrote:
>>>
>>>
>>> 2016-06-27 12:12 GMT+02:00 Tudor Girba <[hidden email]>:
>>> 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."
>>
>>
>>
>>
>>
>

> On Jun 28, 2016, at 6:02 PM, Eliot Miranda <[hidden email]> wrote:
>
>
>
> On Jun 28, 2016, at 8:17 AM, Denis Kudriashov <[hidden email]> wrote:
>
>> Following this "bad idea" we should agree that smalltalk metaclass system is horrible and class should be just a language artifact
>>
> Are you being serious or sarcastic?
>
>> 28 июня 2016 г. 11:45 пользователь "Jan Vrany" <[hidden email]> написал:
>>
>>
>> On Mon, Jun 27, 2016 at 1:09 PM, Nicolas Passerini <[hidden email]> wrote:
>>>
>>>
>>> On Mon, Jun 27, 2016 at 1:44 PM, Denis Kudriashov <[hidden email]> wrote:
>>>
>>> 2016-06-27 13:28 GMT+02:00 Nicolas Passerini <[hidden email]>:
>>> That is not quite true, annotations are (kind of) objects but you can not put behavior in them, just define attributes and optionally default values for those attributes.
>>>
>>> Ah, you are right. I remember many restrictions was applied to them which always forced me to hate Java :)
>>>
>>> Yep.
>>
>> Well, there's a reason why they're restricted. Note, that the restriction is on language level, not at runtime level. A annotation class
>> with arbitrary code would pass JVM verification (or at least I can't see a rule that would reject such a class).
>>
>> When I implemented annotation support I was initially thinking the same - let's create an instance of CoolAnnotationClass when the code is accepted
>> and then one can add arbitrary code to his CoolAnnotationClass. I quickly realized this is a (very) bad idea. Or, to be precise, it is a bad idea given the
>> environment. So I'd be very careful..
>>
>> Jan
>>
>> P.S.: As for "which always forced me to hate Java": I found myself a very enlightening to think carefully about why somebody else
>> do things differently before I start to hate her/him. Besides, there's whole lot of things that Java guys got right...
>>
>>

> On Jun 27, 2016, at 7:55 PM, Eliot Miranda <[hidden email]> wrote:
>
> Hi Doru,
>
> On Mon, Jun 27, 2016 at 6:36 AM, Tudor Girba <[hidden email]> wrote:
> 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).
>
> Well, there already /is/ a meta-object called Pragma, and it gets instantiated when one accesses the compiled method via pragmas:
>
> (CompiledMethod allInstances detect: [:m| m pragmas size > 1]) pragmas collect: [:ea| {ea. ea class}] {{<export: true> . Pragma} . {<var: #tablePtr type: 'int *'> . Pragma}}
>
> So we could add the information you want to Pragma, and have it be lazy.  The Pragma could go search for the defining class-side pragma methods and use the parser to extract the comment(s) when asked.  Hence simple access to pragmas, interested only in the selectors for applying, wouldn't have their performance be impacted.
>
>
> 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.
>
> This pseudo-meta-object (Pragma) can sty ill be causally connected, in the same way that a MethodReference can be causally connected.  The causation is things like "remove", "recompile", but that's dubious.  It's essentially a read-only relationship; one wants to be able to locate the method from the pragma, but changing the method from the pragma isn't necessarily a good idea.  Would you agree that convenience methods like "remove" on MethodReference are a bad idea and one should stick to the removeSelector: protocol on Behavior and ClassDescription?
>
>
> What do you think?
>
> Have I and enough coffee to scramble my thoughts might be a more pertinent question ;-)
>  
>
> Cheers,
> Doru
>
>
> > On Jun 27, 2016, at 2:39 PM, Eliot Miranda <[hidden email]> wrote:
> >
> > Hi Doru,
> >
> >> On Jun 27, 2016, at 3:52 AM, Tudor Girba <[hidden email]> 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 <[hidden email]> wrote:
> >>>
> >>>
> >>> 2016-06-27 12:12 GMT+02:00 Tudor Girba <[hidden email]>:
> >>> 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."
>
>
>
>
>
>
>
>
> --
> _,,,^..^,,,_
> best, Eliot

>
>
> On Tue, Jun 28, 2016 at 8:53 PM, stepharo <[hidden email]> wrote:
> > When I implemented annotation support I was initially thinking the
> > same - let's create an instance of CoolAnnotationClass when the
> > code is accepted
> > and then one can add arbitrary code to his CoolAnnotationClass. I
> > quickly realized this is a (very) bad idea. Or, to be precise, it
> > is a bad idea given the
> > environment. So I'd be very careful..
> > can you explain your statement?
>
> Let me try, this is tricky for me as I'm not good at explaining :-) 
>
> The problems pop out when one need to load the code back. If
> <coolish: 100> gets parsed and stored in
> an annotation container as instance of class Coolish (at compilation
> time),  this means that you just
> introduced a dependency from package of the method which contains the
> annotation to the package of
> Coolish class. This is not (or rather was not in my case) desirable,
> because I need/want to annotate
> methods in kernel with annotations for tools. Kernel should not
> depend or tools - I believe we agree on
> that :-) Note, that this is less of a problem for Java since Java
> loads all code lazily, on demand and in a defined
> way. I personally found it very nice  - though it has some
> (solvable?) issues when this lazy loading is used in Smalltalkish 
> environment such as STX:LIBJAVA)
>
> You can indeed parse them and store them as raw data and convert them
> on demand in reflective
> API. Then, if the class is not available what to do? Return an
> instance of generic Pragma? 
> Throw an error? When one starts to put an arbitrary code into the
> annotation object itself it's either
> processing  code only access data  or it somehow fiddles about the
> annotation itself and/or (worse!)
> about the method itself. The latter results in difficult to debug
> problems as the time the code is executed
> is undefined (if you use lazy instantiation to avoid dependency
> problem). This may be fine with 
> most Smalltalkers as there are other pieces of code that execute
> randomly in an undefined order and still 
> very few complain :-) but I did not want to make things even worse. 
> For the former, mere data-accessing processing code, I don't see much
> of a difference by putting it 
> somwhere else. Follows the same logic as visitor, instead of putting
> code to nodes, you put them
> to extra visitor class. 
>
> Eliot's design elegantly avoid these problems (the same way Java does
> :-) by simply having one defined
> structure which keeps the logical type of the annotation as data (the
> selector of the message send).
> It has other problems, but not the one above. 
>
> Not sure if it makes sense, but I did my best :-) I'm not saying it's
> not solvable and you cannot have
> class per annotation type, but it is not **that** easy to get it
> right. This is my experience over the years. 
>
> HTH, Jan
>
> >
> > Stef
> >
> >
> >
> > Jan
> >
> > P.S.: As for "which always forced me to hate Java": I found myself
> > a very enlightening to think carefully about why somebody else
> > do things differently before I start to hate her/him. Besides,
> > there's whole lot of things that Java guys got right...
> >
> >
> >

> On Jun 27, 2016, at 7:55 PM, Eliot Miranda <[hidden email]> wrote:
>
> Hi Doru,
>
> On Mon, Jun 27, 2016 at 6:36 AM, Tudor Girba <[hidden email]> wrote:
> 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).
>
> Well, there already /is/ a meta-object called Pragma, and it gets instantiated when one accesses the compiled method via pragmas:
>
> (CompiledMethod allInstances detect: [:m| m pragmas size > 1]) pragmas collect: [:ea| {ea. ea class}] {{<export: true> . Pragma} . {<var: #tablePtr type: 'int *'> . Pragma}}

>
> Cheers,
> Doru
>
>
> > On Jun 27, 2016, at 2:39 PM, Eliot Miranda <[hidden email]> wrote:
> >
> > Hi Doru,
> >
> >> On Jun 27, 2016, at 3:52 AM, Tudor Girba <[hidden email]> 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 <[hidden email]> wrote:
> >>>
> >>>
> >>> 2016-06-27 12:12 GMT+02:00 Tudor Girba <[hidden email]>:
> >>> 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."
>
>
>
>
>
>
>
>
> --
> _,,,^..^,,,_
> best, Eliot

> On Jun 30, 2016, at 1:08 PM, Tudor Girba <[hidden email]> wrote:
>
> Hi,
>
>> On Jun 27, 2016, at 7:55 PM, Eliot Miranda <[hidden email]> wrote:
>>
>> Hi Doru,
>>
>> On Mon, Jun 27, 2016 at 6:36 AM, Tudor Girba <[hidden email]> wrote:
>> 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).
>>
>> Well, there already /is/ a meta-object called Pragma, and it gets instantiated when one accesses the compiled method via pragmas:
>>
>> (CompiledMethod allInstances detect: [:m| m pragmas size > 1]) pragmas collect: [:ea| {ea. ea class}] {{<export: true> . Pragma} . {<var: #tablePtr type: 'int *'> . Pragma}}
>
> Yes I know :). An instance of Pragma denotes an concrete annotation of a method. I now would like a meta-object that describes all Pragma instances having the same selector. For example, the protocol on the class side of the Pragma class is actually a query protocol that is better suited for the instance side of a PragmaDescription meta-object. For example:
>
>    Pragma class>>allNamed: aSymbol in: aClass
>
> would become
>
>    PragmaDescription>>pragmasIn: aClass
>
> and you would use it like:
>
>    (PragmaDescription named: aSymbol) pragmasIn: aClass
>
> Creating an instance of PragmaDescription would imply searching the image for the <pragma:> definition.

>> So we could add the information you want to Pragma, and have it be lazy.
>
> It does not quite belong to the Pragma. A comment is common to all Pragma instances, and having it duplicated at the instance level is less elegant.
>
> But, looking for the users (all senders of the pragma selector - the methods that use the annotation) of a Pragma would be even less inconvenient to have on the instance side of Pragma.
>
>
>> The Pragma could go search for the defining class-side pragma methods and use the parser to extract the comment(s) when asked.  Hence simple access to pragmas, interested only in the selectors for applying, wouldn't have their performance be impacted.
>
> The design sketched above would require no runtime penalty for a Pragma instance. All code that works now would work identically afterwards. We would only have one selector in Pragma to get the corresponding description:
>
> Pragma>>description
>    ^ PragmaDescription named: self selector
>
> Alternatively, we could modify the compilation to associate the PragmaDescription in an inst var of a Pragma instance. So, CompiledMethod>>pragmas would always return instances of Pragmas with a PragmaDefinition inst var.
>
> I think I would start with the lazy lookup first, and this would disturb nothing from the current behavior.

>
>
>> 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.
>>
>> This pseudo-meta-object (Pragma) can sty ill be causally connected, in the same way that a MethodReference can be causally connected.  The causation is things like "remove", "recompile", but that's dubious.  It's essentially a read-only relationship; one wants to be able to locate the method from the pragma, but changing the method from the pragma isn't necessarily a good idea.  Would you agree that convenience methods like "remove" on MethodReference are a bad idea and one should stick to the removeSelector: protocol on Behavior and ClassDescription?
>>
>>
>> What do you think?
>>
>> Have I and enough coffee to scramble my thoughts might be a more pertinent question ;-)
>
> :)
>
> Cheers,
> Doru
>
>
>>
>> Cheers,
>> Doru
>>
>>
>>> On Jun 27, 2016, at 2:39 PM, Eliot Miranda <[hidden email]> wrote:
>>>
>>> Hi Doru,
>>>
>>>> On Jun 27, 2016, at 3:52 AM, Tudor Girba <[hidden email]> 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 <[hidden email]> wrote:
>>>>>
>>>>>
>>>>> 2016-06-27 12:12 GMT+02:00 Tudor Girba <[hidden email]>:
>>>>> 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."
>>
>>
>>
>>
>>
>>
>>
>>
>> --
>> _,,,^..^,,,_
>> best, Eliot
>
> --
> www.tudorgirba.com
> www.feenk.com
>
> "Not knowing how to do something is not an argument for how it cannot be done."
>
>