Re: You said the J word

[Paul Haahr <haahr@mv.us.adobe.com>]

> Well, Byron and Paul, how were you thinking of implementing a rewritable
> read-eval loop? Let's look at that, and see what facilities we might need
> to write a job-control system in an ES script.

oh, something like

	fn-forever = while {}
	catch @ e msg {
		if {~ $e error} {
			echo >[1=2] $msg
		} {
			echo >[1=2] uncaught exception: $e $msg
		}
		throw retry
	} {
		forever {
			if {!~ $#fn-prompt 0} {
				prompt
			}
			local (cmd = <>{%parse $prompt}) {
				if {~ $#cmd 0} {
					break
				}
				$cmd
			}
		}
	}

for the default interactive loop.  possible additions:

	- additional special exceptions (sigwinch, maybe)
	- print of bad or non-0 statuses
	- additional hooks like prompt
	- anything you feel like

i can't promise that the above code will work in 0.75, but something like it  
will.  if you notice, the only thing that's missing for this to work is %parse is  
not exposed yet.  also, we haven't decided whether it's only the interactive repl  
that is redefinable or both interactive and non-interactive.  if it's both,  
they'll probably be available under different names, with a strong recommendation  
to not change the non-interactive one.

other open issues:

	- is history handled inside this loop? (probably yes)
	- what happens when the user hits return at the prompt,
	  with just an empty line. (probably %parse does not return
	  and reprompts)

as to job control, if you can figure out how to do it, great, but i'm not sure i  
believe it's possible.  i'd be happy to be proven wrong, but my guess is that  
really supporting job control is going to require work throughout the shell.