Re: [stack] A Joy VM in OCaml

.. continued fron previous post, because the mailer objected to the
complete text.
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Because I'm an isolated researcher, I appreciate when others expose
the route to their results, rather than just giving the 'show-room'
end product.  Perhaps some see this as indiscreet exhibitionism ?

As an example of how I'd like open-collaborative projects to be,
I'm going to NOW try to expose how I partially achieved a nasty task
using unix's cat-like facilities.

TASK DESCRIPTION: find which [if any] Desktop, VT pair is currently 'open' at
the correct directory, to process the newly arrived email, news, http ...etc.

Think of a system from 200 years ago, where 10 to 20 sheets for 6 to 8
categories are distributed between 4 clerks. Clerk1 may have 4 sheets for:
vegetables, meat, clothing, meat.
When a transaction for meat arrives, it should be directed to the clerk
who currently has the/a 'meat' sheet.

Since this is a computer and not paper-sheets, multiple clerks/processes
can have the same sheet/directory open.  And muliple copies of a sheet/directory
may be open for reading/editing its files. And always allocating new
sheets/VirtualTerminals to the new topic as they arrive would give an explosive
growth of redundant sheets/VTs.

If you had 20 copies of a book, all open, mostly at different pages
and you had to switch between books to see which, if any book was open at
the 'meat page', this would be frustrating; compared to scanning down a list
of (book, page-topic) pairs, to find the/a 'meat' book/page.

So the 1st REFINED TASK DESCRIPTION is:
find which Desktop/VT, if any, has the directory for the newly arrived item.

Then the 2nd REFINED TASK DESCRIPTION 'became':
generate a list of the open directories for the 10 to 20 mc-tasks,
and generate info which relates the (D,V) pair to the  task-directory,
so that by visually scanning the 2 lists the D/V which matches the mc-task
can be found.

As an example this task that I'm writing now, will be in a path/directory
*cat* or *Cat*; and I can see that it's using desktop1, VT4; which I
designate as D,V=1,4.

But when I switch out of this D,V to some other jobs and new info arrives for
the 'cat' topic, I'll have forgotten/lost D,V=1,4.  In fact possibly D,V=1,4
will have been allocated to a different topic.

The 2 sets of info look like this [where I just have to remember that they're
call PT & DV] :-
--> # PT
mc         1477   /mnt/cdrom/Inet
mc         1549   /mnt/cdrom
mc         1593   /mnt/cdrom/Legal/TLC/Aug09
mc         1824   /mnt/cdrom/Legal/TLC/Aug09
mc         2429   /mnt/cdrom/Inet/RSS
mc         8952   /mnt/cdrom/Legal/TLC/UKdefaultJ
mc         9837   /mnt/cdrom/Legal/TLC
mc        13406   /mnt/cdrom/Legal/TLC/UKdefaultJ
mc        13529   /mnt/cdrom/Legal
mc        13570   /mnt/cdrom/Legal/TLC/PreApr09
mc        13925   /mnt/cdrom/AI/Catamorfic
mc        17614   /mnt/cdrom/Legal/TLC/PreApr09/CCnewJudges
mc        24024   /mnt/cdrom/Legal/AudtrFiduc

--> # DV
|-kdeinit(1186)-+-su(1196)---bash(1271)---mc(13529)---bash(13531)
|               |-su(1199)---bash(1303)---linux.oberon.no(14102)
|               |-su(1201)---bash(9009)---mc(13570)---bash(13572)
|               `-su(1203)---bash(9805)---mc(9837)---bash(9839)
|-kdeinit(1188)-+-su(1204)---bash(1335)---mc(1593)---bash(1595)---less.bin(19649)
|               |-su(1207)---bash(1367)---mc(1824)---bash(1826)
|               |-su(1209)---bash(1399)---linux.oberon.no(1431)
|               `-su(1211)---bash(9481)---lynx(17276)
|-kdeinit(1189)-+-su(1213)---bash(2075)---mc(17614)---bash(17616)
|               |-su(1215)---bash(2107)---mc(2429)---bash(2431)
|               |-su(1218)---bash(2139)---mc(13406)---bash(13408)
|               |-su(1222)---bash(2171)---sob(9671)---oberon(9712)
|               `-su(1225)---bash(8919)---mc(8952)---bash(8954)
|-kdeinit(1192)-+-su(1221)---bash(1235)---linux.oberon.no(1441)
|               |-su(1226)---bash(1445)---mc(1477)---bash(1479)
|               |-su(1265)---bash(1517)---mc(1549)---bash(1551)
|               `-su(13889)---bash(13893)---mc(13925)---bash(13927)


This can look a bit overwhelming, but searching for the 'cat', we find
 /mnt/cdrom/AI/Catamorfic
as the 3rd last element, and with a pid-number of: 13925.
And the 2nd info-set has mc(13925) in the 4th/last branch of the node
which has linux.oberon.no(1441) as it's 1st branch.

Which means DV=1,4 as we already know !
Similarly we see that the 2 'tree-branches' which are already allocated
to "Aug09", are D,V=3,1 & D,V=3,2 , via pid=1593 and pid=1824 .


Up till now, I've had to use the hack of puting the 'oberon' in the
N-th VT of the Nth Desktop, in order to see which Desktop a set of
branches represent. Obviously I'd like some kind of 'artificial
intelligence' method to further proccess and just place the D/V pair
next to the corresponding directory-path.  Like so:-
1,2= /mnt/cdrom/Inet
1,3= /mnt/cdrom
1,4= /mnt/cdrom/AI/Catamorfic
 ...etc.

But ! by using successive refinement, one can get the benefit of the
partially working product and finish it later --  or never.

Finally ! let's see [by exposing the details of my thought process]
how this came from cat-style linux facilities.

1. Let's examine the minimalist cat-code to see what it does.
2. where is the code, to be found to examine?
3. since it's executable, linux's "whereis" will show us.
4. do: "whereis PT"   gives us: "PT: /usr/local/bin/PT"
5. and show the contents of the script/executable-code
  ie. "cat /usr/local/bin/PT"  shows the single line:-
 "lsof | grep DIR | grep mc | grep "/".  | cut -b-17,67-"

BTW, this is an example for windows-users of what linux does;
 and truthfully the file/script had several lines of comments
which accumulated during its evolution which I'm excluding.

If I look at the line of: code, I guess this is what it does:
 lsof : list all the open file,
 | grep DIR : but show only the lines containing "DIR"
 | grep mc : and of those show only the lines containing "mc"
 | grep "/". : and of those show only the lines containing
                 "/"<some non 'bad chars'>
     {I NOW don't remember exactly which char=set "." represents}
 | cut -b-17,67- : and show only parts of the line/s, probably cutting-out
    pieces at boundries 17th char & 67th char.

NB. the parts which I'm not NOW sure about should be explained in the
 script's comments.  But I'm not 'sanatizing' and pretending that I know.
-------------
And similarly the cat-like-code for "DV" is:
 pstree -p | cut -b25- | grep su
which apparently does:
 print the process-tree,
 but cut-out and show only part of the lines, apparently from the 25th char
   up to the end,
 and show only lines which contain the string "su".

Which I guess gives the 2nd data structures above.
BTW for 'win users':
if you've previously typed : "cat /usr/local/bin/PT"
  it only needs 3 keystrokes to get: "cat /usr/local/bin/DV"
although I prefer ETH-oberon which works without any keyboard, if need be.

Hopefully this example shows how comfortable it can be to develop a large
class of tasks in a cat-style language.

It would be valuable for me, and possibly for others, if cat-contributors
could refine the above down to a lower level. Ie. the implementation of "grep:
and eg. "tr" in a cat-like language would be valuable.  Frankly I don't even
know how joy implements its control-structures, because I never found a "TOP"
view of what joy was good for.

The basis of the "hello world" approach is that a demonstrable model is
made available as soon as possible; and then later one can see how the actual
characters are printed - at a lower level ?
The top-goal must be exposed before the implementation details.

== Chris Glur.