Re: Es and autocompleting

[Bill Trost <trost@cloud.rain.com>]

Noah Friedman writes:
    Completion is context-sensitive and requires knowledge of grammar
    and syntax, which vary from shell to shell.

    If you have to teach the window system how to do context-sensitive
    completion and history for csh, sh, rc, scsh, etc. you've now moved
    a lot of application-specific knowledge...

The claim has been made that the shell is the best place to do
command-line editing because of application-specific knowledge.

You could reasonably also claim:

	* The debugger is the best place to do command-line editing
	because of application-specific knowledge (such as grammar and
	syntax, variables in the debuggee, ...).

	* The mail client is the best place to do command-line editing
	(grammar and syntax, email addresses, ...).

	* The ftp client is the best place to do command-line editing
	(grammar and syntax, remote filename completion, ...).

As you start adding completion to every program, you get complexity and
code bloat in every program -- except, of course, the ones you haven't spent the
time adding command-line editing to. If the command-line editor is at a level
above the shell (I hesitate to say "window system"), then you get that
editing with *every* program -- even trivial ones like "cat".

Furthermore, if you have the command-line editing above the shell level,
and this level sports some sort of completion mechanism (like rk), then
you can actually have completion mechanisms that can be helpful *across*
the exec barrier.

For example, when I run the command "telnet foo.com smtp", rk might
suggest that the next line I want to type is "ehlo cloud.rain.com",
and then "mail from:".  On the other hand, if I type "telnet foo.com
http", rk can suggest "GET /" as the next thing to type.  (Yes, these
are realistic examples -- I was doing some tiger-team work a few months
back).

Zsh hackers aside, I hope no one suggests that telnet should include
command-line editors for every port you might want to type at, but with
a good higher-level command-line editor, you get this all for free.