Re: Typographical error in draft-klensin-unicode-escapes-00

"Clive D.W. Feather" <clive@demon.net> Mon, 22 January 2007 09:22 UTC

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Date: Mon, 22 Jan 2007 09:22:37 +0000
From: "Clive D.W. Feather" <clive@demon.net>
To: John C Klensin <john-ietf@jck.com>
Subject: Re: Typographical error in draft-klensin-unicode-escapes-00
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John C Klensin said:
>> While these are not incorrect, they are confusing to many
>> readers. ABNF allows you to write these as:
>> 
>>     4HexDigit     and
>>     2Hex-Quad
>> 
>> respectively, and I recommend you do so.
> 
> Clive,  I actually find it less confusing to be explicit about
> the lower and upper bounds.

We may have to agree to disagree. When I see "4*4XXX", it makes me wonder
if the author actually meant "4*" or "*4" and misunderstood the notation.

Incidentally, there's no significance to the groupings of 4 in the \u
notation, so I see little point in introducing "Hex-quad". The term "BMP"
is, as I understand it, deprecated these days. So I would just write:

    EmbeddedUnicodeChar = %x5C.75 4HexDigit / %x5C.55 8HexDigit

or if you really want:

    EmbeddedUnicodeChar = UnicodeShortForm / UnicodeLongForm
    UnicodeShortForm    = %x5C.75 4HexDigit
    UnicodeLongForm     = %x5C.55 8HexDigit

[Note that you omitted the / from your definition.]

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