Assertions

local function add(a,b)
   assert(type(a) == "number", "a is not a number")
   assert(type(b) == "number", "b is not a number")
   return a+b
end

add(10)
―――――
lua: temp.lua:3: b is not a number
stack traceback:
        [C]: in function 'assert'
        temp.lua:3: in local 'add'
        temp.lua:7: in main chunk
        [C]: in ?


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