Re: overriding string __eq as in: if {} == "string"

[Andrew Cagney <andrew.cagney@...>]

On 16 June 2015 at 13:04, Dirk Laurie <dirk.laurie@gmail.com> wrote:
> 2015-06-16 17:42 GMT+02:00 Andrew Cagney <andrew.cagney@gmail.com>:

>> The objective here is to fully integrate my objects into Lua.  That
>> is, expressions such as:
>>   o = "string"
>>   i = i+1
>>   if i == 1 or o == "string" then
>
> The first line creates a value of type string and stores it in _ENV.o
> unless you have overridden __newindex in _ENV, a risky thing to do.
> And as the docs state, __eq will not be invoked in the third line.

Yes, I'm taking that risk. __index and __newindex are overridden.
That way things like:

print(a,b)   -- global __index creates values for "a" and "b" on-demand
a = b        -- update "a" with b using __setindex

work the way I'd like.

> What you can do is to redefine stuff not normally used for strings.
> E.g. you can redefine string_mt.__not to be a constructor for your
> wrapper type and string_mt.__xor and to be your intended __eq.
> Then the following will work:
>
>    o = ~"string"
>    i = i+1
>    if i == 1 or o ~ "string" then

or as a first cut:

    o == ~"string"

while not, from my personal pov, ideal it does let me move forward.

Andrew

>