Re: ["all"] as an Lvalue?

[Jonathan Goble <jcgoble3@...>]

On Mon, Mar 28, 2016 at 8:55 PM, Steve Litt <slitt@troubleshooters.com> wrote:
> =====================================================
> domain_props = {
>     ["all"] = {
>         enable_scripts          = false,
>         enable_plugins          = false,
>         enable_private_browsing = false,
>         user_stylesheet_uri     = "",
>     },
>     ["youtube.com"] = {
>         enable_scripts = true,
>         enable_plugins = true,
>     },
> }
> =====================================================
>
> It looks like domain_props is a table whose two elements are each
> tables, named ["all"] and ["youtube.com"] respectively. I've never seen
> something like ["all"] being the name of a table element or a variable
> name before. What's going on, is ["all"] an anonymous table containing
> element "all"? I just don't understand this syntax, and why somebody
> would do this. What am I missing?

No, the keys are ordinary string values. So the first one could also
be accessed as `domain_props.all`. The `[]` syntax here is just a way
to use an arbitrary expression as a table key; it's not needed for
"all", since that is a valid identifier, but it is necessary to use
the string "youtube.com" as a table key, since that string is not a
valid identifier.

Thus, this piece of code could also be written as:

domain_props = {
    all = {
        ["enable_scripts"]      = false,
        ["enable_plugins"]      = false,
        enable_private_browsing = false,
        user_stylesheet_uri     = "",
    },
    ["youtube.com"] = {
        enable_scripts = true,
        ["enable_plugins"] = true,
    },
}

Both domain_props tables, in your example and mine, are exactly identical.