(unknown charset) Re: [BLACKBOX] EBNF question

From: (unknown charset) [at]} <Alexander>
Date: Thu, 16 Feb 2012 03:59:14 +0400

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Hello, Bob!

> this is not strictly on topic, but since EBNF is one of Wirth's languages I
> hope people won't feel too angry with me for raising it here.

  Excuse me for providing reasons of impossibility, rather than solving the
  problem, but I think that the property that makes EBNF suitable for defining
  syntax is the same one that prevents it from being useful in your case.
  I'm talking about the property of binding a correct position for a token to
  the necessity of the token. A token can't be made necessary without defining
  its precise position (or a fixed number of positions) relative to other tokens.
  Not in EBNF.

  You want to make a list of tokens necessary without defining their positions.
  You'll have to either invent a syntax for that, or check for the presence of
  all the necessary tokens elsewhere, for that is not a syntax, but rather a
  semantic check. It does not set the rules for relative positions of tokens
  (which is syntax), it sets rules for the contents of a file (which is
  semantics).

  At least, that's my understanding of EBNF, which, I must admit, may be far
  from reality, for I don't have much practical experience with it.

---===---
 юКЕЙЯЮМДП

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Received on Thu Feb 16 2012 - 00:59:14 UTC