Re: Alternative E loader

On Fri, 2010-02-19 at 14:04 -0500, Kevin Reid wrote:
> On Feb 19, 2010, at 12:23, Thomas Leonard wrote:
[...]
> >> On Feb 19, 2010, at 10:45, Thomas Leonard wrote:
> >>
> >>> If accepted, it could also be used by rune to load the main program.
> >>> This would allow all E programs to import emaker files from the same
> >>> directory without any extra configuration (e.g. rune -cpa ...).
> >>
> >> Per capability design principles, programs should not get automatic
> >> read authority to what happens to be in the same directory.  
> >> However, a
> >> "run the program which consists of this module-directory's main entry
> >> point" or other invocation mechanism which explicitly specifies *that
> >> the directory access should exist* would be reasonable.
> >
> > OK. Though I'm not too worried about this case. If it's a single
> > script.e then it already has <file>, and using <this:...> is just a  
> > way
> > to pass the read authority to other files, as it could have done  
> > anyway.
> 
> Oh. Right. That is not an issue, yes.

For discussion, I've put up changes to do this on my "rune-this" branch:

http://gitorious.org/~tal-itinnov/repo-roscidus/it-innovation/commits/rune-this

This builds on the previous changes (adding ELoader and refactoring
eLauncher). The changes are:

- If you run "rune file.e", <this> will allow importing other E source
code from the same directory as "file.e". Files imported this way will
also get a reference to <this>.

- If you use --src or "rune -", <this> will load files from the current
directory. This is useful for interactive use.

If you run "rune file.emaker" (or use --confine), the <this> loader will
not be available.


This makes it easy to write multi-file modules without messing with
classpath. e.g.

$ cat somepath/foo.emaker  
traceln("Hello from foo!")

$ cat somepath/runetest.e 
traceln("main!")
<this:foo>

$ rune somepath/runetest.e 
=== 2010-03-12T11:44:29.078Z (Traceln.traceit:Traceln.java:90) WRN
__main: 
> main!
 : (traceln)
 @ Traceln#run(String)
 @ run/1: <.../somepath/runetest.e#:span::1:7::1:7>
=== 2010-03-12T11:44:29.282Z (Traceln.traceit:Traceln.java:90) WRN
__main$foo: 
> Hello from foo!
 : (traceln)
 @ Traceln#run(String)
 @ run/1: <.../somepath/foo.emaker#:span::1:7::1:7>


For projects that have multiple modules, each module can be given its
own <this>, to load just its own files. It's up to the main program to
wire the other modules together.


Note: this adds an extra argument to makeEvalContextAuthor.emaker. I
could add a run method with the old signature if anyone else is using
it. The only use I could see was updoc (which I changed to pass null).
Though probably updoc scripts should get a <this> as well.

Thoughts?


-- 
Dr Thomas Leonard
IT Innovation Centre
2 Venture Road
Southampton
Hampshire SO16 7NP

Tel: +44 0 23 8076 0834
Fax: +44 0 23 8076 0833
mailto:tal-v5nx5w6akNyLE8xUarVfuPLx9OUvmyODWmv/[email protected]
http://www.it-innovation.soton.ac.uk