Re: Parsers for extensible grammars?

From	Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP>
Newsgroups	comp.arch.embedded
Subject	Re: Parsers for extensible grammars?
Date	2014-10-26 01:05 +0000
Organization	A noiseless patient Spider
Message-ID	<m2hhcb$abn$1@dont-email.me> (permalink)
References	(3 earlier) <m2anti$mp3$1@speranza.aioe.org> <m2f0av$ku0$1@dont-email.me> <m2foj0$34r$1@speranza.aioe.org> <m2g0oj$au3$1@dont-email.me> <m2gm65$egq$1@speranza.aioe.org>

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On 2014-10-25, Don Y <this@is.not.me.com> wrote:
> On 10/25/2014 4:15 AM, Simon Clubley wrote:
>>
>> Commands can exist outside of the above infrastructure if one wishes;
>> they are called foreign commands and are treated pretty much like a
>> Unix command would be - there's no validation of options prior to
>> the executable starting and hence there's no nicely pre-parsed options
>> and option values ready to be read from within the program itself.
>
> You can *freely* mark any command as either type?  I.e., can I mark
> a command that relies on the DCL stuff for option parsing as a FOREIGN
> command?  And, thus, screw it up (at runtime)?
>

Yes, but it would fail in a clean way with a status code returned from
the CLI routine called by the program to return the (non-existent)
pre-parsed information.

The idea behind pointing you to the DCL CLD material was to give you
some possible ideas about how extendable CLIs with validated options
are handled in another environment (ie: VMS).

Like I said at the time, it's not an exact match for your requirements
but I thought you might be interested in seeing how a similar problem
was handled in VMS, including the syntax used in the command definition
file (and compare it to how the problem is fully pushed to the executable
itself in Unix land).

>>
>> IOW, having foreign commands available as an option doesn't stop you
>> from also having the native DCL integrated approach. If you try to run
>> a DCL integrated executable as a foreign command, no values will be
>> available to read from within your program so you are forced to run it
>> via the DCL mechanism above which means you also get the DCL level
>> validation as well.
>
> So, this (DCL) mechanism is meant as an *aid*/service -- not as a means
> of ensuring software integrity (?).
>

It's a way of expressing an expected structure for a command line which
can be somewhat validated by DCL before the program even starts and
provides a robust, operating system level, method for a program to
obtain command line parameters and options in a way (and with
functionality) that leaves getopt and friends standing in the dust.

The relevance here is that I've encountered people who have never
been exposed to the VMS way of handling this and who think that ad-hoc
getopt style functionality is the only _possible_ way to parse command
lines. I just wanted to make reference to another way of doing this in
case it gave you some ideas even though there's probably nothing you
can _directly_ use here.

Sometimes Don you leave your questions wide open, presumably in order
to invite a wide range of options in response, including ones you had
never even considered. The difficulty with that is that sometimes it's
hard to understand what additional unspoken constraints might exist. :-)

Simon.

-- 
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980s technology to a 21st century world

Thread

Parsers for extensible grammars? Don Y <this@is.not.me.com> - 2014-10-22 12:14 -0700
  Re: Parsers for extensible grammars? Don Y <this@is.not.me.com> - 2014-10-22 12:17 -0700
  Re: Parsers for extensible grammars? Tim Wescott <seemywebsite@myfooter.really> - 2014-10-22 15:13 -0500
    Re: Parsers for extensible grammars? Don Y <this@is.not.me.com> - 2014-10-22 22:54 -0700
      Re: Parsers for extensible grammars? Stefan Reuther <stefan.news@arcor.de> - 2014-10-23 18:36 +0200
        Re: Parsers for extensible grammars? Don Y <this@is.not.me.com> - 2014-10-23 12:10 -0700
      Re: Parsers for extensible grammars? Tim Wescott <seemywebsite@myfooter.really> - 2014-10-23 13:45 -0500
        Re: Parsers for extensible grammars? Don Y <this@is.not.me.com> - 2014-10-23 12:15 -0700
      Re: Parsers for extensible grammars? jim.brakefield@ieee.org - 2014-10-24 07:05 -0700
        Re: Parsers for extensible grammars? Don Y <this@is.not.me.com> - 2014-10-24 08:04 -0700
  Re: Parsers for extensible grammars? Clifford Heath <no.spam@please.net> - 2014-10-23 08:22 +1100
    Re: Parsers for extensible grammars? Don Y <this@is.not.me.com> - 2014-10-22 23:25 -0700
    Re: Parsers for extensible grammars? George Neuner <gneuner2@comcast.net> - 2014-10-23 04:45 -0400
      Re: Parsers for extensible grammars? Don Y <this@is.not.me.com> - 2014-10-23 04:14 -0700
        Re: Parsers for extensible grammars? George Neuner <gneuner2@comcast.net> - 2014-10-23 16:49 -0400
          Re: Parsers for extensible grammars? Don Y <this@is.not.me.com> - 2014-10-24 07:38 -0700
            Re: Parsers for extensible grammars? George Neuner <gneuner2@comcast.net> - 2014-10-26 03:47 -0400
              Re: Parsers for extensible grammars? Don Y <this@is.not.me.com> - 2014-10-26 08:41 -0700
                Re: Parsers for extensible grammars? George Neuner <gneuner2@comcast.net> - 2014-10-26 14:36 -0400
                Re: Parsers for extensible grammars? Don Y <this@is.not.me.com> - 2014-10-26 12:37 -0700
                Re: Parsers for extensible grammars? George Neuner <gneuner2@comcast.net> - 2014-10-26 18:54 -0400
        Re: Parsers for extensible grammars? Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP> - 2014-10-25 02:02 +0000
          Re: Parsers for extensible grammars? Don Y <this@is.not.me.com> - 2014-10-25 01:56 -0700
            Re: Parsers for extensible grammars? Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP> - 2014-10-25 11:15 +0000
              Re: Parsers for extensible grammars? Don Y <this@is.not.me.com> - 2014-10-25 10:21 -0700
                Re: Parsers for extensible grammars? Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP> - 2014-10-26 01:05 +0000
                Re: Parsers for extensible grammars? Don Y <this@is.not.me.com> - 2014-10-25 19:37 -0700
  Re: Parsers for extensible grammars? Andrew Smallshaw <andrews@sdf.lonestar.org> - 2014-10-23 20:04 +0000
  Re: Parsers for extensible grammars? Les Cargill <lcargill99@comcast.com> - 2014-10-23 22:30 -0500
    Re: Parsers for extensible grammars? rickman <gnuarm@gmail.com> - 2014-10-25 13:36 -0400
      Re: Parsers for extensible grammars? Les Cargill <lcargill99@comcast.com> - 2014-10-25 13:14 -0500
        Re: Parsers for extensible grammars? rickman <gnuarm@gmail.com> - 2014-10-25 14:23 -0400
          Re: Parsers for extensible grammars? Les Cargill <lcargill99@comcast.com> - 2014-10-26 00:50 -0500
          Re: Parsers for extensible grammars? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-10-26 19:21 +0000
            Re: Parsers for extensible grammars? rickman <gnuarm@gmail.com> - 2014-10-26 15:29 -0400
  Re: Parsers for extensible grammars? Paul E Bennett <Paul_E.Bennett@topmail.co.uk> - 2014-10-24 09:56 +0100
    Re: Parsers for extensible grammars? Don Y <this@is.not.me.com> - 2014-10-24 07:46 -0700
      Re: Parsers for extensible grammars? Don Y <this@is.not.me.com> - 2014-10-25 19:54 -0700
        Re: Parsers for extensible grammars? Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP> - 2014-10-26 12:15 +0000
          Re: Parsers for extensible grammars? Don Y <this@is.not.me.com> - 2014-10-26 09:02 -0700
            Re: Parsers for extensible grammars? rickman <gnuarm@gmail.com> - 2014-10-26 12:13 -0400
    Re: Parsers for extensible grammars? rickman <gnuarm@gmail.com> - 2014-10-25 13:35 -0400
      Re: Parsers for extensible grammars? Paul E Bennett <Paul_E.Bennett@topmail.co.uk> - 2014-10-26 01:29 +0100
        Re: Parsers for extensible grammars? rickman <gnuarm@gmail.com> - 2014-10-25 21:11 -0400

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