Re: [Json] Proposed minimal change for strings

[John Cowan <[e-mail]>]

Paul Hoffman scripsit:

> Proposal 1 (allow all code units in their unescaped form):
>
>     A string is a sequence of zero or more Unicode code units [UNICODE].

I object to this, because "code unit" is not well defined without
mentioning its size.  I suppose it is 16-bit code units that are meant,
but if so, that must be said.  "If Parliament does not mean what it says,
it must say so."

> In section 2.2 (Strings):
>   Leave the production for "unescaped" as-is.
> In section 3 (Encoding):
>   Add "Some strings, notably those that have unescaped surrogate code units
>   (value 0xD800 to 0xDFFF), cannot be encoded in UTF-8."

While this statement is true, it is not the whole truth, which is that
unescaped surrogate code units cannot be encoded in *any* encoding.
Indeed, it is useless to permit unescaped surrogate code units at all.
Therefore, I reject this proposal in toto.

> Proposal 2 (prohibit unescaped surrogates):
> 
> In section 1 (Introduction):
>   A string is a sequence of zero or more Unicode scalar values [UNICODE].
> In section 2.2 (Strings):
>   Change the production for "unescaped" to be:
>     unescaped = %x20-21 / %x23-5B / %x5D-D7FF / %xE000-10FFFF

I approve of this proposal.

-- 
John Cowan  [e-mail]   http://ccil.org/~cowan
"The exception proves the rule."  Dimbulbs think: "Your counterexample proves
my theory."  Latin students think "'Probat' means 'tests': the exception puts
the rule to the proof."  But legal historians know it means "Evidence for an
exception is evidence of the existence of a rule in cases not excepted from."