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Re: [ietf-822] [abnf-discuss] Wherefore no HTAB in literal text strings in ABNF

Sean Leonard <dev+ietf@seantek.com> Fri, 19 August 2016 02:46 UTC

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From: Sean Leonard <dev+ietf@seantek.com>
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Date: Thu, 18 Aug 2016 19:47:03 -0700
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To: Paul Overell <paul@bayleaf.org.uk>
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Subject: Re: [ietf-822] [abnf-discuss] Wherefore no HTAB in literal text strings in ABNF
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> On Aug 15, 2016, at 2:02 AM, Paul Overell <paul@bayleaf.org.uk> wrote:
> 
> 
> 
> On 15/08/16 02:34, Sean Leonard wrote:
>> Hello Knowledgeable ABNF Folks:
>> 
>> I have been working with RFC 5234 lately. What is the rationale (or what are the rationales) for including SP %d32 but excluding HTAB %d9 in char-val, aka the literal text string? I am sure that this decision was not an oversight.
>> 
>> It may be appreciated that the comment production is defined as WSP, which includes HTAB.
>> 
>> 
> 
>    char-val       =  DQUOTE *(%x20-21 / %x23-7E) DQUOTE
>                                 ; quoted string of SP and VCHAR
>                                 ;  without DQUOTE
> 
> So that the contents of a string literal are visible and unambiguous to a human reader - spaces and tabs look alike.  For comments is doesn't matter if the white space comprises of spaces or tabs, it doesn't change the meaning of a comment.  But for strings it's important for a human reader to know exactly what's in them. 
> 
> 
> Regards
> -- 
> Paul Overell

Thank you. That was one of the justifications that I was thinking, and what I was looking for.

Best regards,

Sean

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