aumouvantsillage/minimal-dsl-racket

This is a minimal Racket program to experiment how the Racket module system can be used in a DSL.

The file main.rkt defines the following macros:

• (assign dest src), where dest is a variable name and src is either a literal or a variable name, expands to a provide form and a define form for the given variable.
• (show src), where src is a variable name, expands to println.
• (use require-spec) is equivalent to a require form in our DSL.
• (begin-mini-dsl body ...) is a wrapper form for our DSL. It calls the check function whose purpose is to perform semantic checking and code transformation.

The function check:

• creates a new scope for the body of the begin-mini-dsl form;
• transforms the destination of each assign form with a generated variable name:
  • a binding is created in the current scope for the original destination name;
  • this binding is mapped to an instance of struct var that stores the generated variable name;
• transforms the source of each assign or show, when the source is a name:
  • by looking up the binding for the source name;
  • by inspecting the corresponding instance of struct var to retrieve the generated variable name.

The relevance of this DSL is not the main concern here.

The question I want to address is: what would be a correct implementation of the use form? We need to provide the bindings that we created in the check function, and we need to access the instances of struct var from the module that contains use forms.

At the moment, the implementation works for a standalone example:

racket examples/standalone.rkt
45

Without a complete implementation, a two-module example will fail in the look-up step:

racket examples/module-main.rkt
main.rkt:43:52: v: variable not found

Uncommenting the syntax-local-lift-provide in function bind-var! will result in the following error:

SIGSEGV MAPERR si_code 1 fault on addr 0x300 Abandon (core dumped)