On Sun, Jul 24, 2016 at 6:18 PM, nobody <nobody+lua-list@afra-berlin.de> wrote:
Why introduce a global concept for something that's just a problem in
some very special cases?
Nil works fine everywhere, except when you expect '{ ... }' to be a
sequence (or you use 'table.pack' and then get that 'n' field that some
people seem not to like...)
I present:
function table.packx( nilsubst, ... ) -- can't think of a good name
local t = table.pack( ... )
for i = 1, t.n do
if t[i] == nil then t[i] = nilsubst end
end
t.n = nil
return t
end
-- (Above function hereby put into the public domain, yadda yadda.)
Ta-daa! You get a sequence, no 'n' field, and _you_ decide what the
substitute should be (of course that can be 'none', 'nothing',
'undefined' or whatever, or maybe just 0, "", ... -- whatever suits your
needs.)
(And if you _must_ share that placeholder across several modules /
libraries / ..., you can have a simple global constant 'none = {}'
(possibly with a metatable to prevent '__index'/'__newindex' etc.), but
you definitely don't need to change the language!)
Except that there's no way to make that substitute value falsey. Thus,
code testing for the lack of a useful value must use explicit equality
tests, rather than simply 'if var then ...', which makes for uglier
code.
I'd rather have a falsey value that's not literally 'false', and for
that, a change to the Lua language is required (be it '__bool' or
'undef').
