Re: __index returns truncated to one, why?

[Dirk Laurie <dirk.laurie@...>]

2014-04-12 15:24 GMT+02:00 duz <duz@sol-3.de>:

> Your arguments against my little proposal are valid when
> looking at tables. I don't think much of them applies to
> the userdata case but likely, nobody would be thrilled if
> metamethods worked subtlety different on different objects.

In the userdata case, metamethods are merely a way of
mapping object methods to Lua syntax. Unfortunately,
"one key, one value" is part of Lua syntax.

    var ::=  Name | prefixexp ‘[’ exp ‘]’ | prefixexp ‘.’ Name

Your proposal exposes a gap if not an ambiguity in the 5.3
manual. The __index metamethod is a function, it must behave
exactly as rawgetting a table would — but it requires deduction.
almost reading between the lines, to extract that information.

The 5.2 manual was clear on the topic, giving pseudocode
for gettable_event. Maybe something like that could be
brought back.