Re: Default to LUA_NOCVTN2S and LUA_NOCVTS2N

[Fangrui Song <i@...>]

On 2019-10-06, Fangrui Song wrote:
> I am a drop-by visitor and just noticed the announcement of Lua 5.4.0 (beta).
> (I wanted to reply to "[ANN] Lua 5.4.0 (beta)" but I am not subscribed,
> thus I do not know its Message-ID so that I can reply by setting the proper In-Reply-To.)
>
> Is there a plan to make LUA_NOCVTN2S and LUA_NOCVTS2N the default, i.e.
> no implicit conversion between numbers/strings?
>
> By making them the default, I envision there might be a need to rename
> LUA_NOCVTN2S and LUA_NOCVTS2N to their opposite forms LUA_CVTN2S and
> LUA_CVTS2N, respectively.

> 8.1 – Incompatibilities in the Language
>
> * The coercion of strings to numbers in arithmetic and bitwise operations
>   has been removed from the core language. The string library does a
>   similar job for arithmetic (but not for bitwise) operations using the
>   string metamethods. However, unlike in previous versions, the new
>   implementation preserves the implicit type of the numeral in the string.
>   For instance, the result of "1" + "2" now is an integer, not a float.

There may be a need to turn off implicit string to number conversion for
this case as well. The behavior corresponds to lstrlib.c stringmetamethods.

 > getmetatable''.__add
 function: 0x55da4540e5dd
 > '3'+'a'
 stdin:1: attempt to add a 'string' with a 'string' # expected
 > '3'+'4'
 7  # unexpected