diff --git a/polymer/eduke32/Makefile b/polymer/eduke32/Makefile
index b4badc991..45ae1ee9c 100644
--- a/polymer/eduke32/Makefile
+++ b/polymer/eduke32/Makefile
@@ -170,7 +170,8 @@ ifneq (0,$(LUNATIC))
                $(OBJ)/luaJIT_BC_lunacon.$o \
                $(OBJ)/luaJIT_BC_geom.$o \
                $(OBJ)/luaJIT_BC_randgen.$o \
-               $(OBJ)/luaJIT_BC_stat.$o
+               $(OBJ)/luaJIT_BC_stat.$o \
+               $(OBJ)/luaJIT_BC_bitar.$o
 
     # now, take care of having the necessary symbols (sector, wall, etc.) in the
     # executable no matter what the debugging level
diff --git a/polymer/eduke32/source/lunatic/bitar.lua b/polymer/eduke32/source/lunatic/bitar.lua
index f5eacfa9e..f92f521ea 100644
--- a/polymer/eduke32/source/lunatic/bitar.lua
+++ b/polymer/eduke32/source/lunatic/bitar.lua
@@ -1,33 +1,18 @@
 
 -- "Bit array" module based on LuaJIT's BitOp.
 
+local ffi = require "ffi"
 local bit = require "bit"
 
 local error = error
+local assert = assert
 local type = type
 
+local setmetatable=setmetatable
+
+
 module(...)
 
--- Create new bit array.
--- Returns a table p in which entries p[0] through p[floor((size+31)/32)]
--- are set to an initialization value: 0 if 0 has been passed, -1 if 1
--- has been passed.
-function new(size, initval)
-    if (type(size) ~= "number" or size < 0) then
-        error("bad argument #1 to newarray (must be a nonnegative number)", 2)
-    end
-
-    if (initval ~= 0 and initval ~= 1) then
-        error("bad argument #2 to newarray (must be either 0 or 1)", 2)
-    end
-
-    local p = {}
-    for i=0,(size+31)/32 do
-        p[i] = -initval
-    end
-
-    return p
-end
 
 -- Is bit i set in bit array ar?
 function isset(ar, i)
@@ -45,3 +30,109 @@ function set1(ar, j)
     local jx = bit.rshift(j, 5)
     ar[jx] = bit.bor(ar[jx], bit.rol(0x00000001, j))
 end
+
+local ops = { isset=isset, set0=set0, set1=set1 }
+local mt
+mt = {
+    __index=ops,
+
+    -- set ops disguised as arithmetic ones...
+
+    __mul = function(ar1, ar2)  -- set intersection
+        assert(#ar1 == #ar2)
+        local p = {}
+        for i=0,#ar1 do
+            p[i] = bit.band(ar1[i], ar2[i])
+        end
+        return setmetatable(p, mt)
+    end,
+
+    __add = function(ar1, ar2)  -- set union
+        assert(#ar1 == #ar2)
+        local p = {}
+        for i=0,#ar1 do
+            p[i] = bit.bor(ar1[i], ar2[i])
+        end
+        return setmetatable(p, mt)
+    end,
+
+    __sub = function(ar1, ar2)  -- set difference
+        assert(#ar1 == #ar2)
+        local p = {}
+        for i=0,#ar1 do
+            p[i] = bit.band(ar1[i], bit.bnot(ar2[i]))
+        end
+        return setmetatable(p, mt)
+    end,
+
+    -- serialization
+    __tostring = function(ar)
+        local maxidx=#ar
+        local size=maxidx+1
+
+        local hdr = "bitar.new('"
+        local ofs = #hdr
+        local totalstrlen = ofs+8*size+2
+        local str = ffi.new("char [?]", totalstrlen)
+
+        ffi.copy(str, hdr, ofs)
+
+        for i=0,maxidx do
+            -- 'a' is ASCII 97
+            for nib=0,7 do
+                str[ofs + 8*i + nib] = 97 + bit.band(bit.rshift(ar[i], 4*nib), 0x0000000f)
+            end
+        end
+
+        ffi.copy(str+totalstrlen-2, "')", 2)
+
+        return ffi.string(str, totalstrlen)
+    end,
+}
+
+-- Create new bit array.
+-- Returns a table p in which entries p[0] through p[floor((maxbidx+31)/32)]
+-- are set to an initialization value: 0 if 0 has been passed, -1 if 1
+-- has been passed.
+-- Storage: 4 bits/bit + O(1)? (per 32 bits: 64 bits key, 64 bits value)
+function new(maxbidx, initval)
+    local p = {}
+
+    if (type(maxbidx)=="string") then
+        -- string containing hex digits (a..p) given, internal
+        local lstr = maxbidx
+
+        local numnibs = #lstr
+        assert(numnibs%8 == 0)
+
+        local size = numnibs/8
+        local maxidx = size-1
+
+        local str = ffi.new("char [?]", numnibs)
+        ffi.copy(str, lstr, numnibs)
+
+        for i=0,maxidx do
+            p[i] = 0
+
+            for nib=0,7 do
+                local hexdig = str[8*i + nib]
+                assert(hexdig >= 97 and hexdig < 97+16)
+                p[i] = bit.bor(p[i], bit.lshift(hexdig-97, 4*nib))
+            end
+        end
+    else
+        if (type(maxbidx) ~= "number" or not (maxbidx >= 0)) then
+            error("bad argument #1 to newarray (must be a nonnegative number)", 2)
+        end
+
+        if (initval ~= 0 and initval ~= 1) then
+            error("bad argument #2 to newarray (must be either 0 or 1)", 2)
+        end
+
+        for i=0,maxbidx/32 do
+            p[i] = -initval
+        end
+    end
+
+    return setmetatable(p, mt)
+end
diff --git a/polymer/eduke32/source/lunatic/bittest.lua b/polymer/eduke32/source/lunatic/bittest.lua
index de22b32d5..0130c4541 100755
--- a/polymer/eduke32/source/lunatic/bittest.lua
+++ b/polymer/eduke32/source/lunatic/bittest.lua
@@ -4,14 +4,14 @@
 
 local string = require "string"
 
-local getticks
-
 local bit = require("bit")
 local bitar = require "bitar"
 
 local print = print
 local tonumber = tonumber
 
+local getticks
+
 if (string.dump) then
     -- stand-alone
     local os = require "os"
@@ -27,8 +27,6 @@ end
 
 -- based on example from http://bitop.luajit.org/api.html
 
-local isset, set0 = bitar.isset, bitar.set0
-
 local m = string.dump and tonumber(arg[1]) or 1e7
 
 local ffiar_p, boundchk_p = false, false
@@ -82,17 +80,35 @@ function sieve()
     local t = getticks()
 
     for i=2,m do
-        if (isset(p, i)) then
+        if (p:isset(i)) then
             count = count + 1
-            for j=i+i,m,i do set0(p, j); end
+            for j=i+i,m,i do p:set0(j); end
         end
     end
 
     print(string.format("[%s] Found %d primes up to %d (%.02f ms)",
                         ffiar_p and "ffi-ar"..(boundchk_p and ", bchk" or "") or "tab-ar",
                         count, m, getticks()-t))
+
+    return p
 end
 
 if (string.dump) then
-    sieve()
+    local p = sieve()
+    local t = getticks()
+
+    -- test serialization
+    local p2 = bitar.new(string.match(tostring(p), "'(.*)'"))
+    print(getticks()-t)
+
+    for i=0,#p do
+        assert(p[i]==p2[i])
+    end
+
+    for i = 3,#p do
+        p[i] = nil
+    end
+
+    print(p)
+    print(p-p)  -- test set difference
 end
diff --git a/polymer/eduke32/source/lunatic/defs.ilua b/polymer/eduke32/source/lunatic/defs.ilua
index 461aae704..3c19a8bb0 100644
--- a/polymer/eduke32/source/lunatic/defs.ilua
+++ b/polymer/eduke32/source/lunatic/defs.ilua
@@ -548,6 +548,7 @@ local allowed_modules = {
     randgen = require("randgen"),
     geom = require("geom"),
     stat = require("stat"),
+    bitar = require("bitar"),
 }
 
 local package_loaded = {}
diff --git a/polymer/eduke32/source/lunatic/dynsymlist b/polymer/eduke32/source/lunatic/dynsymlist
index 94f26c96e..eec417c68 100644
--- a/polymer/eduke32/source/lunatic/dynsymlist
+++ b/polymer/eduke32/source/lunatic/dynsymlist
@@ -43,6 +43,7 @@ luaJIT_BC_con_lang;
 luaJIT_BC_geom;
 luaJIT_BC_randgen;
 luaJIT_BC_stat;
+luaJIT_BC_bitar;
 
 rand_jkiss_u32;
 rand_jkiss_dbl;