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Re: A simple single line, triple-quoted comment is giving syntax error. Why?

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From Ian Kelly <ian.g.kelly@gmail.com>
Date Thu, 26 Mar 2015 17:27:00 -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 12:54 PM, Thomas 'PointedEars' Lahn
<PointedEars@web.de> wrote:
> Ian Kelly wrote:
>> 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
>> […]
>>
>> There is only one expr node, and it contains both STRING tokens.
>
> Prove it.

I'm not going to expend the effort that would be required to go
through the entire Python grammar step-by-step and exhaustively prove
that "foo" "bar" can unambiguously only be produced as a single expr.
If you believe otherwise, show a parse tree that parses these as
separate expressions.

> But be warned: Neither would prove that a string literal is not an
> expression.

I've not claimed that a string literal is not an expression. My claim
is that a literal consisting of the implicit concatenation of more
than one string token is can only be parsed as one expression, not
several. Parsing "foo" "bar"

>  Because you did not consider the most simple variant of an AST
> (or subtree) according to this grammar:
>
>     expr
>      |
>    STRING

Of course I did. This is again *exactly* what I was talking about in
reference to parsing the individual strings in isolation.

> Again, “STRING+” does _not_ mean “STRING STRING STRING*”; it means “STRING
> STRING*”.  The second and following STRINGs are *optional*.

Please stop speaking down to me. I'm quite familiar with basic concepts of EBNF.

>>> […] in the used flavour of EBNF the unquoted “+” following a goal symbol
>>> clearly means the occurrence of *at least one* of the immediately
>>> preceding symbol, meaning either one *or more than one*.
>>
>> It means one or more *tokens*, not one or more literals.
>
> Utter nonsense.  Have you ever written a parser?  (I have.)

Yes.

>  A literal *is*
> a token.  Whether two consecutive tokens end up as the same *node* in an AST
> is a *different* issue (that, again, was _not_ debated).

I was going to respond with a comment about how literals are a type of
expression, not token, using a literal tuple as an example of a
literal that is not a token. Then I checked the docs and noticed that
the language reference actually shies away from calling this a literal
and uses the phrase "container display" instead. Browsing through the
specifications of a few other languages (e.g. ECMAscript, which has
so-called "object literals"), they all seem to share the pattern of
using "literal" strictly to mean a type of token in their specs,
despite the word taking on a much broader meaning when writing
informally. So I'll have to concede that point as well.

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Thread

A simple single line, triple-quoted comment is giving syntax error. Why? Aditya Raj Bhatt <adityarajbhatt@gmail.com> - 2015-03-18 10:46 -0700
  Re: A simple single line, triple-quoted comment is giving syntax error. Why? Laurent Pointal <laurent.pointal@laposte.net> - 2015-03-18 19:04 +0100
    Re: A simple single line, triple-quoted comment is giving syntax error. Why? Laurent Pointal <laurent.pointal@laposte.net> - 2015-03-18 19:06 +0100
      Re: A simple single line, triple-quoted comment is giving syntax error. Why? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-03-18 20:53 +0100
        Re: A simple single line, triple-quoted comment is giving syntax error. Why? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-03-18 20:56 +0100
        Re: A simple single line, triple-quoted comment is giving syntax error. Why? Terry Reedy <tjreedy@udel.edu> - 2015-03-18 17:47 -0400
        Re: A simple single line, triple-quoted comment is giving syntax error. Why? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-19 09:58 +1100
          Re: A simple single line, triple-quoted comment is giving syntax error. Why? Chris Angelico <rosuav@gmail.com> - 2015-03-19 10:23 +1100
    Re: A simple single line, triple-quoted comment is giving syntax error. Why? Aditya Raj Bhatt <adityarajbhatt@gmail.com> - 2015-03-18 11:23 -0700
      Re: A simple single line, triple-quoted comment is giving syntax error. Why? Igor Korot <ikorot01@gmail.com> - 2015-03-18 14:45 -0400
      Re: A simple single line, triple-quoted comment is giving syntax error. Why? Laurent Pointal <laurent.pointal@laposte.net> - 2015-03-18 20:08 +0100
      Re: A simple single line, triple-quoted comment is giving syntax error. Why? Tim Roberts <timr@probo.com> - 2015-03-28 16:34 -0700
  Re: A simple single line, triple-quoted comment is giving syntax error. Why? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-03-18 21:21 +0100
  Re: A simple single line, triple-quoted comment is giving syntax error. Why? Tim Chase <python.list@tim.thechases.com> - 2015-03-18 13:15 -0500
  Re: A simple single line, triple-quoted comment is giving syntax error. Why? Ben Finney <ben+python@benfinney.id.au> - 2015-03-19 11:06 +1100
  Re: A simple single line, triple-quoted comment is giving syntax error. Why? Denis McMahon <denismfmcmahon@gmail.com> - 2015-03-19 00:53 +0000
    Re: A simple single line, triple-quoted comment is giving syntax error. Why? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-03-22 04:14 +0100
      Re: A simple single line, triple-quoted comment is giving syntax error. Why? Chris Angelico <rosuav@gmail.com> - 2015-03-22 14:36 +1100
        Re: A simple single line, triple-quoted comment is giving syntax error. Why? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-03-22 04:49 +0100
          Re: A simple single line, triple-quoted comment is giving syntax error. Why? Chris Angelico <rosuav@gmail.com> - 2015-03-22 15:11 +1100
            Re: A simple single line, triple-quoted comment is giving syntax error. Why? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-03-26 05:35 +0100
              Re: A simple single line, triple-quoted comment is giving syntax error. Why? Ian Kelly <ian.g.kelly@gmail.com> - 2015-03-25 23:09 -0600
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-03-26 17:45 +0100
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Ian Kelly <ian.g.kelly@gmail.com> - 2015-03-26 12:29 -0600
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-03-26 19:54 +0100
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Ian Kelly <ian.g.kelly@gmail.com> - 2015-03-26 17:27 -0600
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-03-28 19:20 +0100
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Ian Kelly <ian.g.kelly@gmail.com> - 2015-03-29 01:56 -0600
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-03-29 12:41 +0200
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Ian Kelly <ian.g.kelly@gmail.com> - 2015-03-31 01:23 -0600
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? sohcahtoa82@gmail.com - 2015-03-31 16:10 -0700
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Chris Angelico <rosuav@gmail.com> - 2015-04-01 10:36 +1100
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Ian Kelly <ian.g.kelly@gmail.com> - 2015-03-31 17:43 -0600
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-04-02 23:31 +0200
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? sohcahtoa82@gmail.com - 2015-04-02 15:26 -0700
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-02 18:21 -0600
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-03 16:40 +1100
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Chris Angelico <rosuav@gmail.com> - 2015-04-03 16:57 +1100
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Marko Rauhamaa <marko@pacujo.net> - 2015-04-03 10:13 +0300
                r"\"" ??? (was A simple single line, triple-quoted comment) Rustom Mody <rustompmody@gmail.com> - 2015-04-03 05:52 -0700
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                Re: r"\"" ??? (was A simple single line, triple-quoted comment) Rustom Mody <rustompmody@gmail.com> - 2015-04-03 08:14 -0700
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-03 09:25 -0600
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Ian Kelly <ian.g.kelly@gmail.com> - 2015-04-03 00:40 -0600
                Re: A simple single line, triple-quoted comment is giving syntax   error. Why? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-03-27 11:43 +1300
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-03-28 19:06 +0100
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Ian Kelly <ian.g.kelly@gmail.com> - 2015-03-26 12:32 -0600
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-03-26 19:56 +0100
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-27 10:15 +1100
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Tim Chase <python.list@tim.thechases.com> - 2015-03-26 18:47 -0500
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Ian Kelly <ian.g.kelly@gmail.com> - 2015-03-26 19:38 -0600
                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Marko Rauhamaa <marko@pacujo.net> - 2015-03-27 07:34 +0200
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                Re: A simple single line, triple-quoted comment is giving syntax error. Why? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-03-26 18:30 +0100
          Re: A simple single line, triple-quoted comment is giving syntax error. Why? Marko Rauhamaa <marko@pacujo.net> - 2015-03-22 12:00 +0200

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