Re: Tuples and other constant values

[Andrew Starks <andrew.starks@...>]

On Wednesday, July 8, 2015, Dirk Laurie <dirk.laurie@gmail.com> wrote:
> 2015-07-07 0:13 GMT+02:00 Coda Highland <chighland@gmail.com>:
> > A large proportion of the tuple users I've met are Python converts.
>
> 2015-07-08 2:34 GMT+02:00 Tim Hill <drtimhill@gmail.com>:
> > You can think of them as an aggregate constant.
>
> Very well put.
>
> I'll confess to being an apostate from Python myself, but this is not
> really a Python thing. Even C89 has constant arrays (ie tuples) and
> structures (ie aggregate constants).
>
> The main reason why aggregate constants would be nice to have in
> Lua is that more lurking bugs can be caught at compile time.

This is one of those invaluable bonus threads. I've heard OF tuples but I didn't know what they were and I still don't comprehend their apparent significance. If anyone (on or off list) would like to point me to their favorite "Why Should I care about Tuples" document, please do. I've been googling it with "okay" results. 

I don't think I saw this earlier, but given the following:

function Tuple(...)

  local co = coroutine.wrap(function (...) while true do coroutine.yield(...) end end )

  return co, co(...) 

end

t = Tuple("foo", 5)

---

This start is missing a way for two Tuple objects with the same arguments to be evaluated as equal.

Beyond that, there is nothing about them that implies that I should be able to, for example, add them, or whatever?

And so also... If I can modify a value in a tuple, then the result would be a new tuple:

--assuming some Tuple library....

t.foo == 10
t2 = t:set("foo", 5)

t2.foo == 5

t2 ~= t

t.foo == 10

---

And so a Tuple might be any object that produces a new object if it is modified? (or errors?)[1]

The benefit being an object that behaves like a basic type, when it comes to equality?

Lua strings are tuples, correct? 

I should use them In places where I would otherwise need to do deep inspection, etc.?

In other languages, tuples may hint a compiler or otherwise provide efficiency benefits?

If the above is correct, I may only be missing the ability to recognize when I should reach for them.[2]

-Andrew

[1]LHF made an int64 library for Lua 5.2 that worked like this and it confused me at first. 

[2]Canonical examples would be welcomed (especially if they include negative examples (where their absence hurts or where they might be misapplied)