The functionality you describe—in particular, setting up clean evaluation
contexts—sounds a lot like what the "Run" button already does. Unless you
have some other notion of "running" in mind for programs in your DSL, I
think what you describe could be accomplished nicely with a "main"
submodule, which (as you may know) is run only when its enclosing module is
invoked as a main program, not when it is required as a library. One
benefit is that this would make this functionality independent of DrRacket.
To illustrate what I mean, your source program:
#lang hypothetical-lanugage
(hypothetical-code)
would be transformed by the reader into:
(module example hypothetical-lanugage
(#%module-begin
(hypothetical-code)))
Then, your `#%module-begin` macro might expand to something like:
(module example hypothetical-lanugage
(#%plain-module-begin
(provide shape)
(define shape (hypothetical-code))
(module* main racket/base
(require (submod "..")
hypothetical-lanugage/private/render)
(render shape))))
What I'm most unsure of about your question is that you say you want to use
a "C++ library that contains a function that takes in a module object as
input." Do you mean that you want to use the Racket C API
<https://docs.racket-lang.org/inside/Writing_Racket_Extensions.html#%28part._.Declaring_a_.Module_in_an_.Extension%29>
to create a new primitive module or something? That is not a very common
thing to do. Racket modules are not first-class values. While you can
produce a value representing the compiled form of a module (`
compiled-module-expression?
<https://docs.racket-lang.org/reference/Module_Names_and_Loading.html?q=module%20compi#%28def._%28%28quote._~23~25kernel%29._compiled-module-expression~3f%29%29>`)
by doing something like:
(compile '(module foo racket/base))
that is rarely what you want to do. In particular, the result of calling
`eval` is not a module (unless of course you do something like `(eval
'(compile '(module foo racket/base)) (make-base-namespace))`.
Calling `eval` on a module form, compiled or otherwise, merely declares the
module: it doesn't immediately do anything. For example, this expression:
(let ([ns (make-base-namespace)])
(eval '(module effects racket/base
(println "running"))
ns)
(println "module evaluated")
(eval '(require 'effects) ns))
prints:
"module evaluated"
"running"
because the module isn't run until the `require` form is evaluated. Also,
`eval` handles expanding the program already: manual expansion is only
needed if you want to do some kind of static analysis.
-Philip
On Tue, Jun 25, 2019 at 6:02 PM Kshitij Sachan <kshitijsacha...@gmail.com>
wrote:
> I'm working on a DSL to represent 3D geometrical shapes. I'm adding a
> language-specific plugin (toolbar button) that should: 1) expand the source
> code to get a module object, 2) evaluate the module object, 3)
> dynamic-require that module object, 4) Create an OpenGL Context, 5)
> render this object using a C++ library that contains a function that takes
> in a module object as input and generates in the existing OpenGL context.
>
> Suppose my geometrical shape code is as follows:
> #lang hypothetical-lanugage
>
> (hypothetical-code)
>
> I have a couple questions on how to set this up:
>
> 1. The documentation on drracket:eval:expand-program
>
> <https://docs.racket-lang.org/tools/drracket_eval.html#%28def._%28%28lib._drracket%2Ftool-lib..rkt%29._drracket~3aeval~3aexpand-program%29%29>
> is rather dense, and I don't understand what the parameters should
> be. Could you please provide me with a minimum working example of how to
> call this function?
> 2. Is the output of drracket:eval:expand-program
>
> <https://docs.racket-lang.org/tools/drracket_eval.html#%28def._%28%28lib._drracket%2Ftool-lib..rkt%29._drracket~3aeval~3aexpand-program%29%29>
> directly
> suitable to be called as the argument to the eval function? If not,
> what kind of preprocessing do I need to do before calling eval?
> 3. Will the result of eval be a module object?
> 4. If I press the toolbar button twice, will dynamic-require work or
> do I need dynamic-rerequire? Essentially what I'm asking is do I get a
> clean evaluation context each time I press my toolbar button?
> 5. Is it good style for my button to save the source code each time I
> run it? If so, how can I do that?
> 6. Ideally, I'd like the OpenGL rendering to appear as a third window
> to accompany the interactions and definitions window. Is there any way to
> do that?
>
> Thanks!
>
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