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From: Ian Kelly <ian.g.kelly@gmail.com>
Date: Thu, 26 Mar 2015 12:29:02 -0600
Subject: Re: A simple single line, triple-quoted comment is giving syntax error. Why?
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On Thu, Mar 26, 2015 at 10:45 AM, Thomas 'PointedEars' Lahn
<PointedEars@web.de> wrote:
> Ian Kelly wrote:
>> What the grammar that you quoted from shows is that STRING+ is an
>> expression. The individual STRINGs of a STRING+ are not expressions,
>> except to the extent that they can be parsed in isolation as a
>> STRING+.
>
> How did you get that idea?  STRING+ means one or more consecutive STRING
> tokens (ignoring whitespace in-between), which means one or more consecut=
ive
> string literals.  A (single) string literal definitely is an expression a=
s
> it can be produced with the =E2=80=9Cexpr=E2=80=9D goal symbol of the Pyt=
hon grammar (given
> there in a flavor of EBNF).

Yes, that's what I was referring to in my parenthetical "except..." above.

What I mean is that if you construct a parse tree of "foo" "bar" using
that grammar, it looks like this:

     expr
       |
    STRING+
     /   \
STRING  STRING

Not like this:

    expr
     |
   STRING+
    /  \
 expr  expr
  |      |
STRING  STRING

There is only one expr node, and it contains both STRING tokens.

>> By the same token, a STRING+ is a single string literal, not
>> an aggregate of several.
>
> No, in the used flavour of EBNF the unquoted =E2=80=9C+=E2=80=9D followin=
g a goal symbol
> clearly means the occurrence of *at least one* of the immediately precedi=
ng
> symbol, meaning either one *or more than one*.

It means one or more *tokens*, not one or more literals.