sunday afternoon whishlist: append/stream operator

[Oliver Schmidt <oschmidt_do_not_send_email_to_this_address@...>]

Hi,

On 09/05/10 17:36, Klaus Ripke wrote:
> Could x[] be syntactic sugar for x[#x+1] ?
> It would make appending to lists so much nicer.

I also think that a nice syntactic form for appending to lists would 
increase Lua's usability as configuration language.

Consider the use case, that the user has to configure some lists of 
names (e.g. filenames) for some kind of processing. Some names may 
belong to different lists. So it would be nice, if the user may define 
his own lists and build configuration lists together from his user 
defined lists. So the user can group his names and mention each name 
only once.

IMHO a nice way for this could be a stream operator "<<" (this could 
also be useful for other use cases).

E.g.

    t1 = { "a", "b", "c"}
    t2 = { "x", "y" }

    t1 << { "d", "e" } << "f" << t2 << "z"

Would result in t1 pointing to the table { "a", "b", "c", "d", "e", "f", 
"x", "y", "z" }

The stream operator should be overwritable in the metatable, with 
default implementation:

    function __stream(a, b)
        if type(a) ~= "table" then error("...") end
        if type(b) == "table" then
            for i = 1, #b do
                a[#a + 1] = b[i]
            end
        else
            a[#a + 1] = b
	end
        return a
    end

What do you think?

Best regards,
Oliver