Re: [ANN] Lua 5.3.0 (work1) now available

[Joshua Jensen <josh.jjensen@...>]

----- Original Message -----
From: Luiz Henrique de Figueiredo
Date: 7/6/2013 12:26 PM
> > The only thing I found that appears to be missing is the ability to
> > determine the actual type of the number.
> One shouldn't need to do this but you can do it as follows:
>
> function isinteger(x)
> 	return tonumber(tostring(x),10)~=nil
> end
This isinteger() function is pretty heavyweight and becomes a garbage 
collection nightmare when operating over a lot of data.  But I guess it 
can be done inefficiently.

In any case, I wouldn't go so far as to say one shouldn't need to know 
the type of the number.  There are a number of reasons for this.  Most 
of my ideas deal in serialization; another example is below.  However, I 
can also think of cases where I want to ensure the incoming arguments to 
a function are integers.  Related to serialization is proper reflection.

Perhaps there could be a subtype() function or even an extension of 
type() that either returns two values 'number' and 'integer' or that 
takes an extra argument to return the actual numeric type?

-- Write nifty binary format
input =
{
    these_are_floats = { 1.0, 2.0, 3.0, 4.0, 5.0 },
    these_are_integers = { 1, 2, 3, 4, 5 },
    these_are_strings = { "one", "two", "three", "four", "five" },
}

function WriteBinaryBlob(data)
    if type(data[1]) == 'number' then
        if subtype(data[1]) == 'integer' then
            return struct.pack(string.rep('I', #data), unpack(data))
        else
            return struct.pack(string.rep('f', #data), unpack(data))
        end
    elseif type(data[1]) == 'string' then
        return struct.pack(string.rep('s', #data), unpack(data))
    end
end

for key, value in pairs(input) do
    WriteBinaryBlob(value)
end

> > It would be nice if there was a method to do so in Lua itself.  One use
> > case is for serializing integer values to disk in text form properly.
> tostring does this already.
True, but I may choose not to use tostring().

Anyway, thanks for all of your efforts getting this going!

-Josh