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> work has begun on Lua 5.5 A beta version is now available: https://www.lua.org/work/ https://www.lua.org/work/ The main change from 5.4 seems to be the (op

• strenholme 1y ago
  As it turns out, it’s possible with Lua going back to 5.1 to not allow undeclared global variables: https://www.lua.org/pil/14.2.html https://www.lua.org/pil/14.2.html That code looks like this in Lua 5.1: function set(name, val) rawset(_G, name, val or false) end function exists(name) if rawget(_G, name) then return true end return false end throwError = {__newindex = function(self,name) error("Unknown global " .. name) end, __index = function(self,name) error("Unknown global " .. name) end } setmetatable(_G,throwError) Then, to use set("a") -- set"a" also works a = 1
  • ufo 1y ago
    Naturally, the main catch is that this only detects the violation at run-time. It also won't stop you from accidentally overwriting a global variable that already exists.
    • nmz 1y ago
      > It also won't stop you from accidentally overwriting a global variable that already exists. That's also solvable using metatables.
    • Dylan16807 1y ago
      Do the declarations in 5.5 prevent overwriting? That sounds tricky to define and implement.