numericValue for (unicode) characters

[monarch_dodra]

On Saturday, 5 January 2013 at 00:47:14 UTC, H. S. Teoh wrote:
> [...]
>
> I, for one, would love to know why isNumeric != hasNumericValue.
>
>
> T

I guess it's just bad wording from the standard.

The standard defined 3 groups that make up Number:
[Nd] 	Number, Decimal Digit
[Nl] 	Number, Letter
[No] 	Number, Other

However, there are a couple of characters that *are* numbers, but 
aren't in those goups.

The "Good" news is that the standard, *does* define number_types 
to classify the kind of number a char is:
* Null: Not a number
* Digit: Obvious
* Decimal: Any decimal number that is NOT a digit
* Numeric: Everything else.

So they used "Numeric" as wild, and "Number" as their general 
category.

This leaves us with ambiguity when choosing our word:
Technically '5' does not clasify as "numeric", although you could 
consider it "has a numeric value".

I hope that makes sense.