deep_equal.lua

-- Implementation from stackoverflow: answered Sep 22 '14 at 14:32 Hisham H M
function deep_equal(a, b)
   local avoid_loops = {}
   local function recurse(t1, t2)
      -- compare value types
      if type(t1) ~= type(t2) then return false end
      -- Base case: compare simple values
      if type(t1) ~= "table" then return t1 == t2 end
      -- Now, on to tables.
      -- First, let's avoid looping forever.
      if avoid_loops[t1] then return avoid_loops[t1] == t2 end
      avoid_loops[t1] = t2
      -- Copy keys from t2
      local t2keys = {}
      local t2tablekeys = {}
      for k, _ in pairs(t2) do
         if type(k) == "table" then table.insert(t2tablekeys, k) end
         t2keys[k] = true
      end
      -- Let's iterate keys from t1
      for k1, v1 in pairs(t1) do
         local v2 = t2[k1]
         if type(k1) == "table" then
            -- if key is a table, we need to find an equivalent one.
            local ok = false
            for i, tk in ipairs(t2tablekeys) do
               if table_eq(k1, tk) and recurse(v1, t2[tk]) then
                  table.remove(t2tablekeys, i)
                  t2keys[tk] = nil
                  ok = true
                  break
               end
            end
            if not ok then return false end
         else
            -- t1 has a key which t2 doesn't have, fail.
            if v2 == nil then return false end
            t2keys[k1] = nil
            if not recurse(v1, v2) then return false end
         end
      end
      -- if t2 has a key which t1 doesn't have, fail.
      if next(t2keys) then return false end
      return true
   end
   return recurse(a, b)
end