Hi Guillaume
I don't think I can answer your questions, as I'm not a language developer,
but this topic interests me;
What are the Racket Syntax Classes you have implemented? Can you provide an
example?
I'm aware of syntax objects, as a specialised data structure for syntax
manipulation, but despite the 'object' in the 'syntax-object' I don't
believe they are integrated into the main Racket class/object system.
https://docs.racket-lang.org/reference/syntax-model.html#%28tech._syntax._object%29
(This link also has a section on scopes, but I don't know if it is what you
are looking for?)
Kind regards,
Stephen
On Thursday, May 21, 2020 at 5:36:08 PM UTC+1, Guillaume Savaton wrote:
>
> I am a Racket beginner trying to create my own DSL.
> As a long-time user of Xtext and other similar tools in the Eclipse
> ecosystem, I have come to Racket expecting that it would address similar
> concerns.
> At the moment, I have mixed feelings: I find the metaprogramming
> facilities in Racket very effective, but at the same time I am struggling
> to achieve tasks that were supported natively by Xtext.
>
> For those who don't know Xtext, here is a summary of how it works:
>
>- A language project is based on a grammar with attribute annotations.
>- The grammar is converted into a "metamodel", i.e. a set of classes
>where each grammar rule corresponds to a class.
>- A parser is automatically generated. It can convert some source text
>into a "model", i.e. a set of instances of the classes from the metamodel.
>- A model can be manipulated using Java APIs. Specialized languages
>are available to constrain a model, query it, transform it, or generate
>code using templates.
>
>
> In Racket, I have started my language project by reproducing what I would
> have done in Xtext:
>
>- I have created a grammar with bragg
>- I have written a set of syntax classes that play the role of the
>metamodel
>
> Syntax Classes example?
>
>- Syntax objects play the role of the model, and I can get their
>attributes with syntax-parse
>- I have written several macros that can generate Racket code in the
>simplest cases.
>
>
> However, I miss some facilities that Xtext provides out-of-the-box:
>
>- Racket syntax classes do not directly support inheritance.
>- Syntax objects are not tied to syntax classes in a class-instance
>relationship, and I have to use syntax-parse every time I want to read an
>attribute.
>- Xtext automatically creates child->parent references in the
>generated AST. In Racket, it seems that I cannot get the parent of a
> syntax
>object.
>- Xtext provides a default mechanism for resolving named references,
>and a scoping API for languages that need specific scoping rules. The AST
>generated by Xtext is actually an object graph rather than a tree.
>
>
> My main concern is about managing the scopes/lexical contexts in my
> language. I am still browsing the documentation but I have found no library
> or guide that addresses this issue.
> The language examples that I have found are either too simple (their
> scoping rules can be easily mapped to those of Racket through macros), or
> use ad-hoc techniques, so that it is difficult to infer a general
> methodology.
>
> So far, I have made two attempts to work around these issues: (1) by
> creating a metamodel-like data structure using Racket structs, and
> transforming syntax objects into struct instances; or (2) using syntax
> objects only and attaching context data to each of them as a syntax
> property.
> Both have strengths and weaknesses, and I am still feeling that I am not
> using Racket with the right mindset.
>
> I hope I have made my concerns clear. Maybe I can create a small example
> to further illustrate what I want to do and where I am stuck.
> Have you experienced similar concerns in one of your projects?
> What design patterns would you recommend ?
> Do you know any well-commented real-life example that I could use for
> inspiration?
>
> Thanks in advance for your answers.
>
> Guillaume Savaton
>
> N.B: I have also published a similar question at stackoverflow two weeks
> ago, but it still has no answer:
>
> https://stackoverflow.com/questions/61622912/domain-specific-languages-in-racket-compared-to-model-driven-frameworks-such-as
>
>
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