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[!REBOL3 Modules] Get help with R3's module system

Ammon
26-Aug-2010
[77]
Excellent.  I'm looking for guru-level docs.  


If I'm reading this correctly, I will finally have everything I asked 
Carl for (in regards to Object! enhancements) at the '04 Devcon. 
 I'm going to spend some time stubbing out the functions I will need 
to do the advanced IDE tricks I've been wanting to do.  I'll have 
some questions for you once I get some of that done...
BrianH
26-Aug-2010
[78]
I'll be done before then. Yeah, a lot of the proposed object enhancements 
have been done to modules instead. Objects will likely still get 
enhanced in some ways, but modules can better handle a lot of what 
objects were previously used for.
BrianH
22-Sep-2010
[79x2]
In theory, it should be possible for delayed network protocol modules 
to be autoloaded on first use.
The modules that implement the protocols could be delay-loaded and 
registered with the general protocol dispatcher. Then the dispatcher 
could import the module the first time it is needed.
Andreas
22-Sep-2010
[81x3]
Yes. Could be made even simpler, though.
Bundle the modules as what Carl now calls "optionally included". 
Also keep a list of scheme prefix to module name, and just auto-import 
the module from this list when a scheme is used in on of the scheme 
action functions (READ, OPEN, ...).
But well, I guess that in fact is exactly what you also describe 
:)
BrianH
22-Sep-2010
[84x3]
Yup :)
That kind of seamless autoimport is one of the main advantages to 
the import-to-system model of the R3 module system. Even if you did 
explicit import, such as with mixins, the rest of the dependencies 
would be able to be resolved automatically.
You don't necessarily need to explicitly import regular modules in 
order to use them, but you do need to do so for mixins. Mixins are 
like the modules in Maxim's or Gabriele's module systems, more or 
less. As such, mixins will only be used by the kind of advanced programmers 
that already need to write modular code. Regular programmers won't 
need them.
Andreas
22-Sep-2010
[87]
So if, for example, DECODE-CGI is in an "optionally included" (which 
I guess == "delay-loaded") CGI module, DECODE-CGI will be available 
even if you don't import 'cgi first?
BrianH
22-Sep-2010
[88]
A regular, non-delayed module could include a delayed module that 
does the real work. And there are other tricks that can be done.
Andreas
22-Sep-2010
[89]
Well, I personally see not cluttering the "global" namespace with 
those names as a great advantage.
BrianH
22-Sep-2010
[90x3]
A lot of those names won't need to be exported at all. Internal use 
words can stay internal.
The wiki link above has some other ideas for advanced tricks, though 
that page is still being written.
And it's not user-level, so be warned: Here there be dragons :)
BrianH
12-Oct-2010
[93]
OK, the third rewrite of the module system has a few simplifications 
as related to the (unreleased) second rewrite, but it is mostly the 
same design. I will be revising the wiki above with the changes.
Andreas
20-Oct-2010
[94x2]
Now that issues are no long strings but words, maybe we want to revisit 
the decision to introduce EXPORT and HIDDEN keywords. In http://www.rebol.net/r3blogs/0300.html
the main reason not to use #export and #hidden seems to be the nature 
of issues.
I'd actually prefer to use #export and #hidden, as I rather dislike 
the concept of "module keywords".
Pekr
20-Oct-2010
[96]
I think that most of guys did not accept changes to issue dtype ... 
maybe it should be put back to original functionality, no?
Andreas
20-Oct-2010
[97x2]
That is a separate discussion.
Currently we have the issues-as-words, and it does not look like 
they are going away, but rather their semantics be adapted to address 
the concerns raised.
Maxim
20-Oct-2010
[99x2]
*VERY* good catch !!!
pekr, most of whined and tried to put the change in our perspective, 
yes  :-)
shadwolf
21-Oct-2010
[101x2]
Pekr be happy i absolutly don't care about any issue ;) aaaaaaaaaahahahaha
so much of a thing used by 3 guys around the world. That impress 
me.
BrianH
21-Oct-2010
[103]
Well, I hope that we are able to make things good enough for you 
without your help. Wish us luck!
shadwolf
21-Oct-2010
[104]
hum that was the cas before too no? You will need luck that's a sure 
thing.
BrianH
21-Oct-2010
[105]
It wasn't a request for assistance. If you want to help, it will 
be welcomed. If not, we are doing well now. Either way you are free 
to use what we create, or not. Enjoy!
BrianH
22-Oct-2010
[106x5]
Over the last day I have been fleshing out the test suite for the 
new module system. Almost all features have corresponding tests now. 
As soon as we have complete coverage I will try to get the tests 
published somewhere official. FYI, alpha 109 fails a lot of the tests, 
but also in the last day I fixed all of the errors that were causing 
test failures. In theory - I need a new build with the fixes to be 
sure, but code tracing says the behavior matches the tests. In any 
case, the test suite will have full feature coverage before alpha 
110 comes out.
I have also started writing some simple charts to explain the details 
of the design and behavior of the module system. In CSV format. These 
charts helped a lot in the fixing of the problems and implementation 
of the tests. As with the tests, I will try to get the charts published 
somewhere official.
With alpha 109 we got some significant usability revisions to the 
design of the module system, relative to alpha 108:

- The return of unnamed modules. They are now changed to private 
modules (mixins) which aren't stored in the system modules list.

- IMPORT now effectively works a lot like the Needs header in user 
scripts. Most users won't be able to tell the difference.

- The return value of IMPORT block is now a block of the modules 
you imported (but not the modules *they* imported).

- The refinements of IMPORT have been renamed and their behavior 
tweaked to be nicer and more useful - the first API change since 
Carl's original.
  - /no-share: The previous /isolate option. Same behavior.

  - /no-lib: Don't export to the runtime library. Private modules don't 
  do this anyways. Also, don't add to the system modules list.

  - /no-user: Don't export to the user context, even as a private module. 
  When importing to a module, /no-user applies.

- The old /only option was split into /no-lib and /no-user, for more 
control. Specify both if you don't want IMPORT to export anything.

Alpha 110 should bring these changes:

- The above will work properly. With a bunch of specs and charts 
that define what "properly" means. With a full test suite to make 
sure.
For the sake of completeness, here are the highlights of the alpha 
108 changes:

- Script headers can have an options block, a simple block of flag 
words. User extensible.

- The standard script header now has a lot fewer words in it. More 
stuff is optional or in the options block.

- Script compression, either binary and base 64 binary! encoded. 
Automatic, transparent.

- Script checksums, both to verify the script and for IMPORT to compare 
with. Applies to decompressed source.

- An optional script length header field (like http's Content-Length). 
This allows binary script embedding.

- Internal support for getting the end of an embedded script, so 
a multi-loader is possible.

- The 'content and 'isolate header fields are changed to option words. 
The content is still saved to a 'content header field.

- The 'content field, if set, is set to the start position of the 
script proper, even if there is stuff before it.

- The whole system/contexts/system concept is gone, as part of the 
system restructuring. Now we have SYS.

- The system/contexts/exports concept is gone too, replaced by a 
not-module-specific runtime library called LIB.

- The old type: 'extension is now the 'extension header option word. 
The only module type is 'module. And it's optional for most code.

- Mixins are now called "private modules", and are flagged by the 
'private option word. And they can have names.

- Private modules can be added to the system modules list (because 
of the names). This lets them be reused without being reloaded.

- Unnamed modules are now prohibited (until alpha 109, where they 
become private modules that reload every time).

- Delayed modules, which can be partially loaded and then not fully 
made until they are imported. Use the 'delay option word.

- A HIDDEN module source keyword, which applies PROTECT/hide to a 
word or words. Acts like the EXPORT keyword.

- Better errors are triggered when the bad things happen. Including 
new error codes.

- DO and MAKE--MODULE intrinsics are now in sys, as DO* and MAKE-MODULE*. 
No more system/intrinsics.

- DO-NEEDS is no longer exported (it's in sys). IMPORT block is a 
public alias for DO-NEEDS anyways.

- MODULE now makes modules that act more like those in script files. 
And has /mixin support too.

- A whole bunch of changes and fixes to native functions to support 
the above stuff.
Shadwolf's "used by 3 guys around the world" comment brings to mind 
one of the more ironic things about the module system:


Most user code for R3 will be written in "scripts", not "modules". 
This will be even more the case once we get more of concurrency working, 
because "script" code works in the user context, which will be task-local. 
We are going out of our way to make it extremely easy to just use 
"scripts" and not have to bother with "modules".


The ironic part is that "scripts" are just another kind of module, 
one of the three including regular and isolated modules. In particular, 
user scripts are a kind of module that we try to make as non-module-like 
as it is possible to be (given that they run in a module system). 
The entire module system structure is built around the challenge 
of making the module system apparently disappear, or at least be 
something that you can be almost completely ignorant of. The module 
system is built for script programmers, to let people do PITS on 
a systerm that they don't even have to know is capable of the most 
advanced PITL.


So the module system we are discussing here will be used by *everyone 
who programs in R3*, whether they know it or not :)

(I am politely assuming that Shadwolf was not referring to the entire 
REBOL community when he said "3 guys".)
GrahamC
22-Oct-2010
[111x2]
can modules be released as encrypted code ?
Not much point I guess
BrianH
22-Oct-2010
[113]
Not yet, but that is planned. It's even mentioned in the design wiki.
GrahamC
22-Oct-2010
[114]
are modules signed?
BrianH
22-Oct-2010
[115]
Cryptographic signing is also planned, as also mentioned in the wiki. 
Both will work in a similar way to the compression and checksum, 
respectively.
GrahamC
22-Oct-2010
[116]
sha256 ?
BrianH
22-Oct-2010
[117x2]
We plan to do encryption and signing. We aren't far enough along 
in the plan to know how we will do these.
The checksum is CHECKSUM/secure, whatever algorithm that is.
Sunanda
22-Oct-2010
[119]
Checksum/secure is SHA-1
BrianH
22-Oct-2010
[120x2]
In theory, you could generate R3 scripts using R2 and still have 
most of the same features. Loading them would be trickier though.
SAVE is pretty straightforward and doesn't use any R3-specific features.
GrahamC
22-Oct-2010
[122]
Is the cryptography being rehashed from R2 ?
BrianH
22-Oct-2010
[123]
Rehashed :) No, we're using the old hashes :)
GrahamC
22-Oct-2010
[124]
It would be good if certificate use could be more easily enabled
BrianH
22-Oct-2010
[125x2]
I can't say if that will be the case with the encryption or signing 
though.
Certificate use is something R3 doesn't do well yet, afaik (which 
isn't far). We will likely have to do a lot of infrastructure work 
before we can do encryption or signing.