Re: picking, signatures, LCF, and a wee bug...
Andreas Rossberg <AndreasRossberg <at> web.de>
2007-07-04 10:07:05 GMT
From: "Lucas Dixon" <ldixon <at> inf.ed.ac.uk>:
>
> I was not imagining pickling the interactive loop itself, which will
> have a IO stream to stdin/stdout, but the result of it. I know that
> alicec can compile arbitrary ML files (presumably assuming that no
> streams are left open?). So I thought that similar behavior must be
> possible with the a user interaction - just take the users input lines
> as lines in a file that is being compiled. The result would be a
> compiled alice component, which, I thought, was pickleble?
Actually, you do need neither alicec nor pickling to do that, as the
Compiler structure from the Alice library allows you to compile directly
from a string to a first-class component value in memory. You can pass such
values directly to the component manager for evaluation.
Given that, what you describe is pretty much the implementation of the Alice
toplevel. So yes, your suggestion is workable. But admittedly, I do not
fully understand what you are getting at. It seems that what you are
considering boils down to 'using' files by compiling and evaluating them
line by line (or rather, dec by dec). I already proposed something along
these lines in an earlier post:
http://www.ps.uni-sb.de/pipermail/alice-users/2007/000785.html
I think it should be fairly easy to write a wrapper to the 'use' function
that operates that way (i.e., splits the file and then uses each bit
separately). That doesn't even require changing or redoing the toplevel
implementation - just import the wrapper into the toplevel before use-ing
anything.
Obviously, this would be simpler if there was some form of 'useString'
function. Then you'd just do
fun splitSource (s : string) : string list = ... (*) some string hackery
val useStringProper = useString
fun useString src = List.app useStringProper (splitSource src)
fun use file =
let
val f = TextIO.openIn file
val src = TextIO.inputAll f
in
TextIO.closeIn f;
useString src
end
Short of that, you have to create temporary files. Here is a skeleton
(untested):
val useProper = use
fun use file =
let
val f = TextIO.openIn file
val src = TextIO.inputAll f
do TextIO.closeIn f
val srcs = splitSource src
val files = List.tabulate (List.length srcs, fn _ =>
OS.FileSys.tmpName ())
val final = OS.FileSys.tmpName ()
val ffinal = TextIO.openOut final
in
ListPair.app (fn (src, file) =>
let
val f = TextIO.openOut file
in
TextIO.output (f, src);
TextIO.closeOut f;
TextIO.output (ffinal, "do OS.FileSys.remove \"" ^ file ^
"\"\n");
useProper file (*) queue it
end) (srcs, files);
TextIO.closeOut ffinal;
useProper final (*) remove temp files
end
Admittedly, this is quite a hack with all the temporary files. But it should
work. Maybe I'll add a useString function for the next release. 
Hope that helps,
- Andreas
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