Re: numeric captures (string.find)

[Rici Lake <lua@...>]

On 14-Sep-04, at 4:34 PM, Asko Kauppi wrote:

> Would it be hard to make 'string.find()' return true numbers (not 
> strings with numerical contents, as now):
>
> What do you think - would it get any votes?

Not from me :)

First of all, there are many strings of digits which are not "numbers" 
-- id numbers, telephone numbers, postal codes (in some countries), 
credit card numbers, etc. Note that you cannot reliably round-trip such 
a sequence -- it may have too many digits for the precision of Number, 
or it may have leading zeros. So getting a number instead of the string 
loses information.

Furthermore, there are many numbers which are not simply sequences of 
digits -- negative numbers, floating point numbers, etc. The patterns 
to recognise these are complicated; it is actually easier to just match 
the possible character sequence and then verify with tonumber().

I wouldn't object to some % escape that used the c library's numeric 
recognition algorithm and returned a real number -- although I'm not 
sure that it would be worthwhile -- but magic behaviour on (%d+) is not 
a good idea, imho. (And also tricky to check for while parsing the 
pattern string.)

Rici