Author: Stan Eisenstat
Subject: Re: [Cs323] parsley circular definition?
Date: Friday, 18 Sep 2020, 07:32:36

    > Message Posted By: Unknown
    >
    > I'm trying to understand the appendix of parsley, specifically the syntax
    > of [command]. I'm a little confused here -- it seems like [command] relies
    > on [sequence] to be defined, [sequence] relies on [and-or], [and-or]
    > relies on [pipeline], [pipeline] relies on [stage], [stage] relies on
    > [subcmd], and [subcmd] relies on [command]. Is this a circular definition?
    > Or would you keep parsing until which is [simple]?

No, it is not a circular definition.

The expression grammar in the Addendum on Parsing is
similar but simpler:

  [factor]     = VARIABLE / ([expression])
  [term]       = [factor] / [term] * [factor]
  [expression] = [term] / [expression] + [term]

The recursion is necessary to allow expressions like

  a + b * (c + d * (e + f * (g + h * (i + j))))

--Stan-