Re: r6rs libraries

[Ludovic Courtès]

Hello!

Andy Wingo <address@hidden> writes:

> So from 7.2 of R6RS itself:
>
>     An implementation may distinguish instances/visits of a library for
>     different phases or to use an instance/visit at any phase as an
>     instance/visit at any other phase.
>
> Which is to say, "we allow single instantiation" -- as Guile modules
> are.

[...]

>
>     When an identifier appears as an expression in a phase that is
>     inconsistent with the identifier’s level, then an implementation
>     may raise an exception either at expand time or run time, or it may
>     allow the reference.
>
> So, furthermore, it seems that not only may library A be instantiated at
> runtime, /it may be in library B's "import list" as well/. This is what
> happens with Guile's current module semantics.

These both come as a surprise to me, as I had always thought R6RS was
much stricter about phase separation.  That's good news for "pure
interpreters"; extra work would still be needed to handle phases > 0 in
the compiler.

Thanks for the detailed reading!

Ludo'.