Re: Coercion: which do we want in the next version?

[Andrew Starks <andrew@...>]

On Wed, Jul 13, 2016 at 3:11 AM, Dirk Laurie <dirk.laurie@gmail.com> wrote:
> The present situation is that you can when building Lua disable
> automatic conversion between numbers and strings. All it takes
> a line in a section of src/Makefile set aside for user settings.
>
> MYCFLAGS= -DLUA_NOCVTN2S -DLUA_NOCVTS2N
>
> As befits an experimental feature, this is not in the Manual but
> it has been discussed often enough that "everybody" knows it.
>
> There is no direct way to see whether this has been done but it is
> easy to check whether `1 .. 2` or `"1"+"2"` is legal. However, there
> is no way to switch coercion on or off at runtime. The executable
> invoked when you just type 'lua' can behave in one of four possible
> ways. Maybe some of us have two or even four executables for the
> different settings; I will be impressed.
>
> By the time we reach the next version, quite possibly the feature will
> no longer be experimental, therefore documented, and maybe the
> default setting will be different from what it is now.
>
> Personally, I compile with
>
> MYCFLAGS= -DLUA_NOCVTS2N
>
> It offers a wide range of benefits. Since the string metatable can be
> accessed without the debug library, a clean way to implement a DSL
> inside Lua is to use expressions involving strings. especially now
> that Lua 5.3 offers so many more operations.
>
> But it is not so easy if you have to worry all the time whether
> 'str1 ~ str2' might not just decide to xor the bits instead of performing
> whatever cute operation you have been using the syntax for. And if
> you actually like the present behaviour, you can always supply
> a metatable for that.
>
> I can live with -DLUA_NOCVTN2S if I must, but the convenience
> of being able to use table.concat on an array of numbers will be
> sorely missed, and setting a __concat metamethod for numbers
> won't bring it back.
>


I've been using  -DLUA_NOCVTS2N and haven't had any issues with it in
a while. NOCVTN2S was too... pedantic and I had many irritating issues
with that flag and have grown to dislike it.

-Andrew
-- 
Andrew Starks
612 840 2939
andrew@starksfam.org