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- Subject: Re: Lua as (Matlab like) calculator
- From: Dirk Laurie <dpl@...>
- Date: Wed, 29 Jun 2011 16:05:06 +0200
> It is not (as you say) what assignment means in a mathematical
> sense of course.
Don't blame mathematics for what Fortran, Matlab, etc do.
I find Lua's assignment rule simplest of all programming languages I know:
> Tables, functions, threads, and (full) userdata values are objects: variables
> do not actually contain these values, only references to them. Assignment,
> parameter passing, and function returns always manipulate references to such
> values; these operations do not imply any kind of copy.
Two sentences, and the whole concept is fully explained.
It is good that `__assign` is not a metamethod. We'll then need a library
function `rawassign`, and it's not worth it. Copying recursively defined
objects is a complicated matter, and there should be some visible reminder
that one is invoking such a mechanism. After all, it could be as small as
a pair of parentheses.
-- When object b is constructed, set its __call metamethod to make a copy
-- of itself. It could even take an argument indicating the desired depth.
a=b -- `a` is another name for the value of `b`
a=b() -- `a` is a name for a newly-made copy of `b`