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grammarPEG : Grammar <- Definition+ !. what is the !.

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grammarPEG : Grammar <- Definition+ !. what is the !.

In XTreams-Parsing ->PEGParser class->grammarPEG

is a Rule

Grammar <- Definition+ !.

Which I believe means "Only 1 or more definitions and nothing else" where "!." means "nothing else"

I suspect that the !. was put there to radically tighten down the allowed inputs to a PEG grammar.

Is this assumption correct?

thanks in advance.

tty

Levente Uzonyi

Re: grammarPEG : Grammar <- Definition+ !. what is the !.

Hi Tim,

On Thu, 16 Apr 2020, gettimothy via Squeak-dev wrote:

> In XTreams-Parsing ->PEGParser class->grammarPEG
>
> is a Rule
>
> Grammar <- Definition+ !.
>
>
>
> Which I believe means "Only 1 or more definitions and nothing else" where "!." means "nothing else"
>
> I suspect that the !. was put there to radically tighten down the allowed inputs to a PEG grammar.
>
> Is this assumption correct?

IIRC '!.' means end of stream. $! is simple negation. $. is any character.

Levente

>
>
> thanks in advance.
>
> tty
>
>
>
>
>

Chris Cunnington-4

Re: grammarPEG : Grammar <- Definition+ !. what is the !.

In reply to this post by Squeak - Dev mailing list

On Apr 16, 2020, at 9:43 AM, gettimothy via Squeak-dev <[hidden email]> wrote:

Grammar <- Definition+ !.

I think this is just the root definition of the tree after the mandatory Grammar definition. You are allowed one or more further definitions, which is what the + is for. The !. just says nothing else will be processed. To me it almost looks like the root as a no-op, because it just passes on to wherever Definition is defined.

Chris

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------------------- Original Message -------------------
From: Chris Cunnington
Received: Thu Apr 16 2020 13:06:21 GMT-0400 (Eastern Daylight Time)
To: gettimothy via Squeak-dev; tty
Subject: Re: [squeak-dev] grammarPEG : Grammar <- Definition+ !. what is the !.

On Apr 16, 2020, at 9:43 AM, gettimothy via Squeak-dev <[hidden email]> wrote:

Grammar <- Definition+ !.

Chris

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