[Info-vax] Radical command line suggestion

[terry+googleblog at tmk.com]

On Tuesday, March 17, 2015 at 12:45:33 AM UTC-4, JF Mezei wrote:
> Imagine if DCLTABLES.EXE had a short description for each qualifier, it
> should theoretically be possible for DCL to give you a list of valid
> arguments and qualifiers along with short explanation  based on what you
> have entered so far.

I know of 2 different implementations of this sort of thing on VMS:

PMDF - based on MATHLIB
MultiNet

Both of these are a bit "twitchy".

By the way, the Cisco "parser" is not exactly a table-driven parser (or wasn't the last time I looked at it, anyway) - it is more like a set of hard-coded decision trees. And it is complicated further by the presence of 2 types of "hidden" arguments - ones where you need to type enough to uniquely identify the hidden argument and then ? completion works, and ones where you need to spell out the whole argument and completion doesn't work at all. 

It also has a lot of legacy baggage - if a command to do something is "foo bar", the command to undo it might be "no foo bar" or "foo nobar", depending on who implemented it.

That sort of thing also appears in table-driven parsers. One of the more infamous examples is in RSTS/E DCL, where the /NO in /NOfoo is handled at a higher level than the specific argument's processing. This leads to the opposite of "PRINT/NOTIFY" being "PRINT/TIFY"