Re: Next Version of Lua?

[Jim Mellander <jmellander@...>]

Olivier Hamel wrote:
> Roberto Ierusalimschy wrote:
>>> Roberto said they (inner Lua dev group) weren't happy with any known 
>>> implementation of bitwise operators, it would be helpful to know
>>> what  they are not pleased with so we may propose alternate 
>>> solutions/implementations.
>>>     
>>
>> My dream was bitwise operators that make sense for floating numbers,
>> like shifts and negation do. But I gave up.
>>
>> -- Roberto
>>
>>   
> Oh. Well. Yah, you won't be getting very far with bitwise ops on float,
> I suggest that floats be cast to ints (or whatever) and then the ops
> performed on them. It's common knowledge you won't be getting bitwise
> ops on floats natively/naturally unless you add some (a lot) of magic
> powder to the mix with a slice of lemon. But even there, I don't thing
> the idea of bitwise ops can ever EVER apply to floats, since their
> internal representation does not match that of a 'simpler' number like
> char/short/int/etc... That said, I had in mind to use bitwise ops on
> whole numbers anyways...
> 
> Have we considered adding fixed point precision numbers?
> 
> Olivier
> 
> 

My 2nd favorite language (awk as implemented in gawk), which also uses a
double as the numeric type, takes the following tack when doing bitwise ops:

"For all of these functions, first the double-precision floating-point
value is converted to the widest C unsigned integer type, then the
bitwise operation is performed. If the result cannot be represented
exactly as a C double, leading nonzero bits are removed one by one until
it can be represented exactly. The result is then converted back into a
C double. (If you don't understand this paragraph, don't worry about it.)"

from http://www.gnu.org/manual/gawk/html_node/Bitwise-Functions.html

-- 
Jim Mellander
Incident Response Manager
Computer Protection Program
Lawrence Berkeley National Laboratory
(510) 486-7204

The reason you are having computer problems is:

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