Re: A minimal LL(1) parser generator ?

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From	carlglassberg@gmail.com
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Subject	Re: A minimal LL(1) parser generator ?
Date	Sun, 5 Jan 2020 11:59:45 -0800 (PST)
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On Thursday, January 2, 2020 at 10:21:53 AM UTC-8, Anton Ertl wrote:
...
> (( a b && c d && ))

1. For concatenation of these, I would write, in Gray:
   ((a b &&))((c d & &&)) for EBNF: a { b a } c { d c }
because wouldn't
   ((a b && c d & &&))
be the same as?
   a { b a } c { d a { b a } c }

2. Let us compare separator-list notation.

In Waite and Goos, "Compiler Construction", there is an infix operator, "||", for separator list, not to be confused with Gray's meta-symbol for "or".
And Eiffel has a special notation for separator list.

In comparison, Anton's Gray has a postfix operator, "&&", for separator-list.

/Comparison of separator-list notation in
Waite/Goos EBNF, Eiffel EBNF (BNF-E), and Gray EBNF/

                               Wirth EBNF         Gray EBNF:
-------------------------------------------------------------------
Waite/Goos: x || y ==========> x { y x }          x y &&

In Eiffel:  { x y ...}* ===> [ x { y x } ]     (( x y && )) ??
            { x y ...}+ ===>   x { y x }          x y &&
-------------------------------------------------------------------

What is better about Gray is that it only uses braces in action semantics,
in doubled form {{ ... }}, and no one is likely to be confused by the use of
braces.

Also it's postfix separator-list operator, "&&", is easier to remember than
Eiffel's more verbose special variation of standard EBNF braces.

And Gray's "&&" separator-list operator is just another postfix op, consistent with it's use of "??", "**" and "++"

Gray better separates the 2 styles of notation, it's "regular expression" style versus standard bracketed EBNF style.

The 2 styles ideally should not be mixed, or at least confusion should be avoided by not introducing yet another similiar notation, in the form of a special variation of standard EBNF braces for separator lists.

One minor criticism of Gray:

I do wish Gray had a production rule terminator, say semicolon ";" or stop "."

The end of 1 rule would be clearly distinguishable from the beginning of the next without special processing of end-of-line which makes scanning and
parsing space sensitive. We would avoid the need for LL(2) parsing or other
parsing and scanning techniques.

Carl
----

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A minimal LL(1) parser generator ? Andy <borucki.andrzej@gmail.com> - 2019-12-21 19:07 -0800
  Re: A minimal LL(1) parser generator ? arnold@skeeve.com (Aharon Robbins) - 2019-12-22 19:29 +0000
  Re: A minimal LL(1) parser generator ? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2019-12-26 16:21 +0000
    Re: A minimal LL(1) parser generator ? carlglassberg@gmail.com - 2019-12-29 14:47 -0800
      Re: A minimal LL(1) parser generator ? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2019-12-31 16:30 +0000
        Re: A minimal LL(1) parser generator ? carlglassberg@gmail.com - 2020-01-01 01:02 -0800
          Re: A minimal LL(1) parser generator ? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2020-01-02 17:25 +0000
            Re: A minimal LL(1) parser generator ? carlglassberg@gmail.com - 2020-01-05 11:59 -0800
              Re: A minimal LL(1) parser generator ? carlglassberg@gmail.com - 2020-01-05 13:59 -0800
              Re: A minimal LL(1) parser generator ? carlglassberg@gmail.com - 2020-01-05 14:44 -0800
              Re: A minimal LL(1) parser generator ? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2020-01-22 17:12 +0000
                Re: A minimal LL(1) parser generator ? carlglassberg@gmail.com - 2020-01-23 02:41 -0800
                Re: A minimal LL(1) parser generator ? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2020-01-25 18:25 +0000
  Re: A minimal LL(1) parser generator ? gaztoast@gmail.com - 2019-12-31 07:10 -0800
  Re: A minimal LL(1) parser generator ? honey crisis <gaztoast@gmail.com> - 2020-01-02 08:50 -0800
  Re: A minimal LL(1) parser generator ? George Neuner <gneuner2@comcast.net> - 2020-01-02 13:16 -0500
  Re: A minimal LL(1) parser generator ? rockbrentwood@gmail.com - 2020-01-04 10:37 -0800
    Re: A minimal LL(1) parser generator ? honey crisis <gaztoast@gmail.com> - 2020-01-05 05:05 -0800
    Branched gotos was: Re: A minimal LL(1) parser generator ? Christopher F Clark <christopher.f.clark@compiler-resources.com> - 2020-01-06 08:47 +0200
      Re: Branched gotos was: Re: A minimal LL(1) parser generator ? Ben Hanson <jamin.hanson@googlemail.com> - 2020-01-07 11:32 -0800
    Re: A minimal LL(1) parser generator ? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2020-01-22 17:08 +0000
      Re: A minimal LL(1) parser generator ? "Fred J. Scipione" <FredJScipione@alum.RPI.edu> - 2020-01-25 15:27 -0500

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