Re: New operators?

[Rici Lake <lua@...>]

Andy Stark wrote:
> An alternative to assignment operators (+=, etc) might be to have a
> shorthand for referring to the variables on the left hand side of the
> assignment. Perhaps one of the unused characters (question mark, say)
> could be used for this. So if we started with:-
>
>    longVarName = longVarName + 1
>
> ...we could change it to:-
>
>    longVarName = ? + 1
>
> ...and then perhaps ?1, ?2, etc for multiple assignments.

Some time ago, I wrote a patch for Lua which does this (except with
$ instead of ?), which I think is floating around in various places
(not on LuaPowerPatches, though, because I'm not really sure I like
it either.) If you want to play with it (and it comes with absolutely
no guarantees), you can find it at:

http://primero.ricilake.net/lua/pseudo-5.1.2.patch

Note: in a multiple assignment, $ refers to the matching lhs, and $i
refers to the i'th lhs. I'm not certain that the "matching lhs" rule
is correct: it's been suggested that $ should refer to the list of
lhs's, so that you could do a sort of rotate:

  a[x], a[x+1], a[x+2] = $3, $

That indeed might be convenient but right now you'd have to write:

  a[x], a[x+1], a[x+2] = $3, $1, $2

With this notation, ++ can be expressed almost as concisely:

  a[x] =$+ 1

and you can write expressions hard to write in C++, such as:

  a[x] = 2 * $ + 1

  a[x] = func($)

etc.

It does have a certain something going for it....