Space Lua: Align arithmetic model with standard Lua

[mjf]

This patchset aligns Space Lua arithmetic model with standard Lua. It also extends arithmetic test suite for Space Lua.

[zefhemel]

Ok, this is looking simpler than before. As I understand it you do end up using a boxed value (new Number) in the end and do all the conversions around that. Is Number somehow preserving whether a value was an integer or a float? I don't really understand this part.

[mjf]

We only add distinction for zero and only when needed in order to align with Lua. Number itself does not preserve int vs float but we do, via a Symbol tag, on boxed +0 and by recomputing "integerness" for non-zero values.

[mjf]

The code seems to be working as expected (as I hope). There is some code left that may be deduplicated into helper wrappers but I am uncertain about this step for I do not know what the impact of extra function calls to these wrappers would be in terms of performance. It won't be hard to make this step later...

It does not break anything for me and also passes all checks and tests. I also do not see any performance impact personally. Both does not mean there is not some issue left, or some performance regression will occure.

This branch also adds missing __unm and __bnot metamethods. The implementation is still missing the __len and correct #. As I realized the # operator is misbehaving now (as well as the accompanied unimplemented __len metamethod) which should be fixed. But not here. I'd rather create separate FR for it (and perhaps take over it) for it is not strictly speaking an arithmetical operation and it will definitely need some extra work to make it aligned with Lua.

__len: the length (#) operation. If the object is not a string, Lua will try its metamethod. If there is a metamethod, Lua calls it with the object as argument, and the result of the call (always adjusted to one value) is the result of the operation. If there is no metamethod but the object is a table, then Lua uses the table length operation (see §3.4.7). Otherwise, Lua raises an error. -- docs

[zefhemel]

Alright, this works for me. I mostly understand what's happening here. Thanks for the effort!