Re: Default to LUA_NOCVTN2S and LUA_NOCVTS2N

[Fangrui Song <i@...>]

On 2019-10-07, Roberto Ierusalimschy wrote:
> > Is there a plan to make LUA_NOCVTN2S and LUA_NOCVTS2N the default, i.e.
> > no implicit conversion between numbers/strings?
>
> No (at least for now).

That is fine.

There may still be a need to conditionally compile stringmetamethods
with LUA_NOCVTN2S or another macro. See my previous reply.

The incompatibility is introduced in 5.4 . If this is conditioned in
this release, users who define LUA_NOCVTN2S will not see another
incompatibility in this regard when LUA_NOCVTN2S ever becomes the
default.

> > 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