[gambit-list] Gerbil: What's the defsyntax-for-import&/export forms for, e.g. rename-in/out, except-in/out
vyzo at hackzen.org
Tue Oct 22 12:51:16 EDT 2019
Think of it as separation of runtime and compile phase.
A module may have imports and exports that are only visible at compile
time; this is exactly what for-syntax import/export does.
for-template is a little harder to explain, you can think of it as
injecting dependencies in modules who are using your module.
It is useful if you have a module that is designed to be imported
for-syntax (eg macro utilities or procedural macro implementations).
If you generate code that refers to symbols not in your scope but which
must be available at runtime (well, at phi-1 relative to the current phase)
in the module that is importing you, then you import the relevant modules
for-template and the expander does the rest.
On Tue, Oct 22, 2019 at 5:57 PM Adam <adam.mlmb at gmail.com> wrote:
> Ah great, thanks - it's almost fully clear now.
> |for-syntax| and |for-template|, is their motivation that |phi:| takes a
> set of *identifiers* - e.g. (export … (phi: +1 make-protocol-info
> protocol-info? …)) and hence a separate form is needed to import/export
> whole modules on given phi:s and that's what these are for e.g. (export …
> (for-syntax bigmodulename))?
> On Tue, 22 Oct 2019 at 22:24, Dimitris Vyzovitis <vyzo at hackzen.org> wrote:
>> They are documented in the reference:
>> -- vyzo
>> On Tue, Oct 22, 2019 at 5:12 PM Adam <adam.mlmb at gmail.com> wrote:
>>> Hi Vyzo,
>>> The core prelude (
>>> defines some extensions to |import| and |export|.
>>> Bumped into studying this in proto.ss, which contains (export ...
>>> (struct-out !rpc ...) ...).
>>> struct-out can be understood from its use - it's for exporting a
>>> structure with its constructors, accessors, mutators. (struct-out's
>>> definition code is totally unreadable to me though.)
>>> All of these are undocumented, may you want to comment on what they are
>>> for also with a single use example (or add to some documentation section in
>>> your guide)?
>>> - for-syntax
>>> - for-template
>>> - only-in
>>> - except-in
>>> - rename-in
>>> - prefix-in
>>> - group-in
>>> - except-out
>>> - rename-out
>>> - prefix-out
>>> - struct-out
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