Basic Latin digits, not everything else (was: RE: How the C programming language bridges the man-machine gap)

[Hans Åberg]

> On 19 Apr 2022, at 00:24, Marius Spix via Unicode <unicode at corp.unicode.org> wrote:
> 
> Also note >
> 
> On Mon, 18 Apr 2022 21:10:58 +0200
> Jens Maurer via Unicode wrote:
> 
>> On 18/04/2022 20.47, Doug Ewell via Unicode wrote:
>>> Hans Åberg wrote:
>> "In both the source and execution basic character sets,
>> the value of each character after 0 in the above list
>> of decimal digits shall be one greater than the value
>> of the previous."
>> 
>> Note the use of the term "basic character set".
> 
> Also note that SHALL be does not mean MUST be. For example, the basic
> character set SHALL include certain characters like “[”, “]”, “{” or
> “}”, but whenever they do not exist in the current character set, C
> allows to replace them by digraphs and trigraphs. C++ also adds and
> alternative tokens (like “and” or “xor” instead of “&&” or “^”).
> Trigraphs are not supported in C++17 anymore, which breaks
> downwards-compatibility.
> 
> C also expect that the backslash (\, ASCII codepoint 0x5C) is used for
> escape sequences in string literals, but some users of Shift JIS
> encoding use the Yen sign (¥), with shares the same codepoint 0x5C.

In math, it is common that the symbols vary. For example, in logic, one might use for conjunction 𝑨 ∧ 𝑩 or 𝑨 & 𝑩, or implication 𝑨 ⇒ 𝑩, 𝑨 → 𝑩, or 𝑨 ⊃ 𝑩. If defines the logic using a specific set of symbols, it is also valid for other such sets.