Say no to global by default?
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- Subject: Say no to global by default?
- From: Gavin Wraith <gavin@...>
- Date: 2018年7月20日 21:06:52 +0100
I have not read all the correspondence on the
"Say no to globals by default thread" so it could be that
this is redundant. In the latest version of RiscLua I
have a prelude containing:
local D = { }
global = setmetatable ({ }, {
__newindex = function (t, n, v) rawset (_G, n, v) end,
__index = rawget,
})
global ._PROMPT = "> "
setmetatable (_G, {
__newindex = function (t, n, v)
if not D[n] then
local w = debug.getinfo (2, "S").what
if w ~= "C" then
error ("\nattempt to write to undeclared variable " .. n, 2)
end -- if
D[n] = true
end -- if
rawset (t, n, v)
end ,
__index = function (_, n)
if not D[n] then
error ("\nattempt to read undeclared variable " .. n, 2)
end -- if
end,
} )
So the first assignment to a global variable x
has to be
global.x = foo
but before that any reference to x raises an error.
--
Gavin Wraith (gavin@wra1th.plus.com)
Home page: http://www.wra1th.plus.com/