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