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local tonumber, tointeger = tonumber, math.tointeger
local type, getmetatable, rawget, error = type, getmetatable, rawget, error
local strsub = string.sub
local print = print
_ENV = nil
-- Try to convert a value to an integer, without assuming any coercion.
local function toint (x)
x = tonumber(x) -- handle numerical strings
if not x then
return false -- not coercible to a number
end
return tointeger(x)
end
-- If operation fails, maybe second operand has a metamethod that should
-- have been called if not for this string metamethod, so try to
-- call it.
local function trymt (x, y, mtname)
if type(y) ~= "string" then -- avoid recalling original metamethod
local mt = getmetatable(y)
local mm = mt and rawget(mt, mtname)
if mm then
return mm(x, y)
end
end
-- if any test fails, there is no other metamethod to be called
error("attempt to '" .. strsub(mtname, 3) ..
"' a " .. type(x) .. " with a " .. type(y), 4)
end
local function checkargs (x, y, mtname)
local xi = toint(x)
local yi = toint(y)
if xi and yi then
return xi, yi
else
return trymt(x, y, mtname), nil
end
end
local smt = getmetatable("")
smt.__band = function (x, y)
local x, y = checkargs(x, y, "__band")
return y and x & y or x
end
smt.__bor = function (x, y)
local x, y = checkargs(x, y, "__bor")
return y and x | y or x
end
smt.__bxor = function (x, y)
local x, y = checkargs(x, y, "__bxor")
return y and x ~ y or x
end
smt.__shl = function (x, y)
local x, y = checkargs(x, y, "__shl")
return y and x << y or x
end
smt.__shr = function (x, y)
local x, y = checkargs(x, y, "__shr")
return y and x >> y or x
end
smt.__bnot = function (x)
local x, y = checkargs(x, x, "__bnot")
return y and ~x or x
end
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