Captain's Log Supplemental

3. a sudden, intuitive perception of or insight into the reality or essential meaning of something, usually initiated by some simple, homely, or commonplace occurrence or experience.

I actually thanked my mother for dragging my out on a shopping expedition today, because I figured out sometime a ways “down” my todo list: implementing control flow in tpsh. I guess you can take the programmer away from the code, but you can’t take the code away from programmer ^_^ ^_^ ^_^.

Earlier I recorded that the goal was for tpsh to use a queue of commands to execute rather then going by lines, the idea being:

`cmd1; cmd2; cmd3`

would parse into a list like ‘(cmd1, cmd2, cmd3’) which tpsh would then walk, eval, and execute the result in sequence (i.e. first in, first out). Then it occurred to me, if the shell will go that route for lexical reasons: why not implement the shells control flow operators as keywords that manipulate that queue directly? So that conceptually, a shell snippet like:

cmd0
if [ expr ]; then
  cmd1
  cmd2
else
  cmd3
  cmd4
fi
cmd5

would be inserted into the queue in a suitable manor and passed to the call back, so if the queue looked something like this:

( cmd0, if [ expr ], cmd1, cmd2, else, cmd3, cmd4, fi, cmd5 )

the call back would receive that relevant portion of the queue, (i.e. queue₁ through queue₇), evaluate the test and return the appropriate portion to be spliced into the queue, in this case:

( cmd0, cmd1, cmd2, cmd5 ) or ( cmd0, cmd3, cmd4, cmd5 )

depending on whether `[ expr ]` evaluated as true or false.

Damn, this so makes me want to straighten up the necessary parts of tpsh… now if only I didn’t have to work tomorrow from morning to whenever I drop over undead, or pass out lol. These kinds of things have always fascinated me about programming, but life has never offered much chance to study compilers, virtual machines, and interpretors… let along create something like tpsh, that requires implementing a scripting language :. The one good thing, despite the ups/downs and expressiveness of sh script, it’s really an easy language for a human to understand.

hmm, there was something I wanted to add a `set -o option` for, but I can’t remember what the heck it was lol.

man it’s been a slow day… I’ve only made about 15~16 commits on tpsh, one of which was merging branches lol. The main focuses of today’s tinkering has been minor bugfixes (mostly related to and tweaking the completion function.

Previously my completer would just take a quick approach, but always doing completions for built in commands, stored macros, known programs, and filenames. Now it has some notion of *what* it should complete.

$ b^I -> assume it can be anything
$ echo b^ -> assume it’s a file (formally a full eval() was done)
$ builtin l^I -> complete built-in commands
$ alias x -> complete to names in %Macros.

When I get the time, I want to make the completion function have a more hot-plug-in nature to it. A pre-completion hook, completion hook, and post-completion hook; the pre getting to modify the thing before completion, the completion hook being able to totally replace do_completion() aside from the pre/post hooks; and the post-hook having a change to modify the completions being returned. The current working idea is: a TPSH_WHAT_HOOK environment variable being set to A. perl code to generate a CODE ref from, or B. an external program to delegate to. (e.g. TPSH_COMPLETION_HOOK=”compl.rb” would pass compl.rb the necessary data, and expect the program to generate a n delimited list on its stdout for tpsh to parse). Odds are there will be more variables to tune it with later, as well as the API avail. being documented in the manual page My main reason for desiring this style of dynamically configurable completion is so I could do things like, seting up my tpshrc to “ignore” any ‘lost+found’ entries in filename completions; i.e. /usr/local/l^I expands to /usr/local/local not /usr/local/lo – completion list for local / lost+found. I know the zsh (which I use a lot) is noted for it’s configurable completion and spelling correction, but honestly I’ve never customized it beyond the lines zsh’s setup program added to my rc, let along RTFM’d about it lol.

Making it easy to add command sensitive completions through the hooks would be nice too, e.g. `man 2 foo^I` and have a hook spot the man 2 and go about completing foo to manual pages in section 2, hehe. (the only zsh feature I abuse, actually lol)

Really what needs doing atm in tpsh, is cleaning up the lex/eval subroutines and merging them and a few related changes with resolve_cmd(). Basically the principal adjustment needed is to go from line-based handling of commands, to (properly) breaking them lexically for storage into an execution queue. Generally though I like how stuffs coming along, except for a few odds and ends here and there.

At one point,tpsh relied on a list of “this command marks something to skip macro expansion on”, a quick solution until expand_aliases() could be rewritten. One night I found myself working on a scratch file with commands to modify said list (add, rm, and show the non expanding commands list via expr or array slice/index). That’s when I threw my hands up in disguest, and decided tomorrows job would be fixing expand_aliases (note to self: s/aliases/macro/). Imagine if you tried to type ‘unalias ls’ and the shell expanded ls to it’s aliased value, that kinda stuff. Kind a cool to be able to configure that, but kinda wrong to need a linear look up on each pass through the loop (ugh!).

To add built-in commands to manipulate said list rather then fix the problem, just was not something I was NOT willing to do… because to my eyes, it would be like a pox on my honour as a programmer: to gamma-weld such a cheap trick into place with built in commands to configure and abuse it rather then fix it — thus the macro expansion system got re-implemented, much more correctly this time. (didn’t have time to sort positional params and what nots).

I am also VERY glad that tpsh is being developed with git, rather then cvs! (I’ve also spent part of tonight learning more about gits plumbing)

Been working over SSH from SAL1600 today, since my rooms flooded out with cloths racks :. This crappy wireless ain’t helping either, just to keep things stable I’ve had to drop from AES encryption to Blowfish and add compression… either the signal utterly blows these days, or PuTTY must leak a lot of resources me thinks.

I cloned master in /srv/git/Projects/tpsh to /tmp/tpsh to do a little work, when surprise surprise… OpenBSDs perl barfed at Getopt::Long::GetOptionsFromArray. A cursory inspection of installed Perl modules around the network & change logs, showed my worst fear was right: it’s an experimental function added 2 years ago. After inserting a banda-id, and doing quite a bit of testing to avoid regressions… I also fixed a few other bruises and found a few things Perl 5.8.8 / use warnings didn’t like very much.

The birth of the “porting” branch, lol.

After taking care of pushing that out to the shared-repos, I checked out master and implemented the eval built in, so before I start coding tonight on my laptop I’ll need to update the master branch there from the one on the server, and merge in the changes from the porting branch.

Currently I’ve got three versions of Perl installed, 5.8.9 on the FreeBSD laptop (the authoritative git repository), 5.10.0 (activeperl) / 5.8.8 (from msys-git) on Windows XP, and 5.8.8 on the OpenBSD machine (home of the shared repository / insurance policy).

if tihs infernal wireless goes out once more…. I might just start working from my laptop on the couch, and the hell with this P.O.S. At least then, Iw ouldn’t have to SSH to get work done ^_^.

commit b841dc4954c24d0abea43daf407b6bf70e1c450b
Author: Terry ******* ****** <***********@****.***>
Date: Wed Mar 25 07:15:31 2009 +0000

massively improved alias expansions

aliases now expand recursively until resolved or aborted. A circular
alias like x = y; y = z; z = x; will resolve x to x when it hits z. The
expansion of aliases should behave more or less as desired, but without
positonal paramter support

tpsh:
$ alias x=’y -opts P’
$ alias y=’z -flags PP’
$ alias z=’echo z PPP’
$ x one two three
z PPP -flags PP -opts P one two three
zsh:
$ alias x=’y -opts P’
$ alias y=’z -flags PP’
$ alias z=’echo z PPP’
$ x one two three four
z PPP -flags PP -opts P one two three four

At the moment the shell local()’s %ENV before each expansion, and will
likely set 0..$#, $#, $@, and $* accordingly someday; but currently does
not use %ENV for anything. In order to allow macros to change the
environment, we can’t just local() %ENV to implement positional params
for macros, but it will be a suitable stop-gap until done fully.

note: alias, macro, and function all revolve around %Macros and
&expand_aliases for macro expansion.

the next big chore is improving the code that invokes expand_aliases(), lol.