commit 9db58c6b8a47103e80bb85e07618d2bef6a6821d
Author: Bruce Hill <bitbucket@bruce-hill.com>
Date:   Fri Feb 9 02:13:07 2018 -0800

    Initial commit.

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..82a321d
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,50 @@
+# makefile for immutable table library for Lua
+
+# change these to reflect your Lua installation
+LUA= /users/Bruce/Sandbox/Lua/lua-5.1.5
+LUAINC= $(LUA)/src
+LUALIB= $(LUA)/src
+LUABIN= $(LUA)/src
+
+# these will probably work if Lua has been installed globally
+#LUA= /usr/local
+#LUAINC= $(LUA)/include
+#LUALIB= $(LUA)/lib
+#LUABIN= $(LUA)/bin
+
+# probably no need to change anything below here
+CC= gcc
+CFLAGS= $(INCS) $(WARN) -O2 $G
+WARN= -std=c99 -pedantic -Wall -Wextra
+INCS= -I$(LUAINC)
+#MAKESO= $(CC) -shared
+MAKESO= $(CC) -bundle -undefined dynamic_lookup
+
+MYNAME= immutable
+MYLIB= l$(MYNAME)
+T= $(MYNAME).so
+OBJS= $(MYLIB).o
+TEST= test.lua
+
+all:	test
+
+test:	$T
+	$(LUABIN)/lua $(TEST)
+
+o:	$(MYLIB).o
+
+so:	$T
+
+$T:	$(OBJS)
+	$(MAKESO) -o $@ $(OBJS)
+
+$(OBJS): limmutable.c
+
+clean:
+	rm -f $(OBJS) $T core core.*
+
+doc:
+	@echo "$(MYNAME) library:"
+	@fgrep '/**' $(MYLIB).c | cut -f2 -d/ | tr -d '*' | sort | column
+
+# eof
diff --git a/limmutable.c b/limmutable.c
new file mode 100644
index 0000000..ccd0652
--- /dev/null
+++ b/limmutable.c
@@ -0,0 +1,300 @@
+/*
+* immutable.c
+* An immutable table library.
+*/
+
+#include "lua.h"
+#include "lauxlib.h"
+#include "lobject.h"
+#include "ltable.h"
+#include "lstate.h"
+#include <stdio.h>
+
+#define MYNAME "immutable"
+#define MYTYPE MYNAME
+
+// Class:new(...)
+static int Lcreate_instance(lua_State *L)
+{
+    int n_args = lua_gettop(L);
+    // arg 1: class table, ...
+
+    lua_getfield(L, 1, "__fields");
+    // Stack: [__fields]
+    size_t n = lua_objlen(L,-1);
+    if ((size_t)n_args-1 != n) {
+        lua_pushstring(L, "incorrect number of arguments");
+        lua_error(L);
+    }
+    lua_pop(L,1);
+    // Stack: []
+
+    lua_getfield(L, 1, "__instances");
+    // Stack: [__instances]
+    lua_createtable(L, n, 0);
+    // Stack [__instances, inst]
+    
+    // Copy in all the values, and simultaneously compute the hash:
+    lua_Integer hash = 0;
+    for (lua_Integer i=1; i <=(lua_Integer)n; i++) {
+        lua_pushinteger(L, i);
+        lua_pushvalue(L, i+1);
+        // Stack [__instances, inst, i, args[i+1]]
+        lua_Integer item_hash;
+        switch (lua_type(L, -1)) {
+            case LUA_TNIL:
+                item_hash = 0;
+                break;
+            case LUA_TNUMBER:
+                item_hash = (lua_Integer)lua_tonumber(L, -1);
+                break;
+            case LUA_TBOOLEAN:
+                item_hash = (lua_Integer)lua_toboolean(L, -1);
+                break;
+            case LUA_TTABLE:
+            case LUA_TFUNCTION:
+            case LUA_TUSERDATA:
+            case LUA_TTHREAD:
+            case LUA_TLIGHTUSERDATA:
+                item_hash = (lua_Integer)lua_topointer(L, -1);
+                break;
+            case LUA_TSTRING:
+                {
+                    size_t strlen;
+                    const char *str = lua_tolstring(L, -1, &strlen);
+                    item_hash = *str << 7;
+                    for (const char *end = &str[strlen]; str < end; str++)
+                        item_hash = (1000003*item_hash) ^ *str;
+                    item_hash ^= strlen;
+                    break;
+                }
+            default:
+                item_hash = 0;
+        }
+        hash = (1000003 * hash) ^ item_hash;
+        lua_settable(L, -3);
+        // Stack [__instances, inst]
+    }
+
+    // Stack: [__instances, inst]
+    // Find bucket
+    lua_pushinteger(L, hash);
+    // Stack: [__instances, inst, hash]
+    lua_gettable(L, -3);
+    // Stack: [__instances, inst, bucket]
+    if (lua_isnil(L, -1)) {
+        // Make a new bucket
+        // Stack: [__instances, inst, nil]
+        lua_pop(L, 1);
+        // Stack: [__instances, inst]
+        lua_createtable(L, 1, 0);
+        // Stack: [__instances, inst, bucket]
+        lua_createtable(L, 0, 1);
+        // Stack: [__instances, inst, bucket, bucket_mt]
+        lua_pushstring(L, "__mode");
+        lua_pushstring(L, "k");
+        // Stack: [__instances, inst, bucket, bucket_mt, '__mode', 'k']
+        lua_settable(L, -3);
+        // Stack: [__instances, inst, bucket, {'__mode'='k'}]
+        lua_setmetatable(L, -2);
+        // Stack: [__instances, inst, bucket]
+
+        lua_pushinteger(L, hash);
+        // Stack: [__instances, inst, bucket, hash]
+        lua_pushvalue(L, -2);
+        // Stack: [__instances, inst, bucket, hash, bucket]
+        lua_settable(L, -5);
+        // Stack: [__instances, inst, bucket]
+    }
+    // Stack: [__instances, inst, bucket]
+    // scan bucket
+    lua_pushnil(L);
+    while (lua_next(L, -2) != 0) {
+        // Stack: [__instances, inst, bucket, hash_collider_inst, hash_collider]
+        int bucket_item_matches = 1;
+        // Perform a full equality check
+        lua_pushnil(L);
+        // Stack: [__instances, inst, bucket, hash_collider_inst, hash_collider, nil]
+        while (lua_next(L, -2) != 0) {
+            // Stack: [__instances, inst, bucket, hash_collider_inst, hash_collider, collider_key, collider_value]
+            lua_pushvalue(L, -2);
+            // Stack: [__instances, inst, bucket, hash_collider_inst, hash_collider, collider_key, collider_value, collider_key]
+            lua_gettable(L, -7); // inst[collider_key]
+            // Stack: [__instances, inst, bucket, hash_collider_inst, hash_collider, collider_key, collider_value, inst_value]
+            if (!lua_equal(L, -1, -2)) {
+                // go to next item in the bucket
+                bucket_item_matches = 0;
+                lua_pop(L, 4);
+                break;
+                // Stack: [__instances, inst, bucket, hash_collider_inst]
+            } else {
+                lua_pop(L, 2);
+                // Stack: [__instances, inst, bucket, hash_collider_inst, hash_collider, collider_key]
+            }
+        }
+        if (bucket_item_matches) {
+            // Stack: [__instances, inst, bucket, hash_collider_inst, hash_collider]
+            lua_pop(L, 1);
+            // Found matching singleton
+            return 1;
+        }
+    }
+
+    // failed to find a singleton
+    // Stack: [__instances, inst, bucket]
+
+    const void *data = lua_topointer(L, -2);
+    void** userdata = (void**)lua_newuserdata(L, sizeof(void*));
+    *userdata = (void*)data;
+    
+    // Stack [__instances, inst, bucket, inst_userdata]
+    lua_pushvalue(L, 1);
+    // Stack [__instances, inst, bucket, inst_userdata, metatable]
+    lua_setmetatable(L, -2);
+    // Stack [__instances, inst, bucket, inst_userdata]
+    
+    lua_pushvalue(L, -1);
+    // Stack [__instances, inst, bucket, inst_userdata, inst_userdata]
+    lua_pushvalue(L, -4);
+    // Stack [__instances, inst, bucket, inst_userdata, inst_userdata, inst]
+    lua_settable(L, -4);
+    // Stack [__instances, inst, bucket, inst_userdata]
+    return 1;
+}
+
+
+static int Llen(lua_State *L)
+{
+    lua_pushvalue(L, 1);
+    luaL_getmetatable(L, MYTYPE);
+    lua_getfield(L, -1, "fields");
+    return 1;
+}
+
+static int Lindex(lua_State *L)
+{
+    lua_getmetatable(L, 1);
+    // Stack: [mt]
+    lua_getfield(L, -1, "__fields");
+    // Stack: [mt, fields]
+    
+    lua_pushnil(L);
+    while (lua_next(L, -2) != 0) {
+        if (lua_equal(L, -1, 2)) {
+            Table **inst_table = (Table**)lua_touserdata(L, 1);
+            lua_Integer i = lua_tointeger(L, -2);
+            const TValue* value = luaH_getnum(*inst_table, i);
+            setobj2s(L, L->top - 1, value);
+            return 1;
+        }
+        lua_pop(L, 1);
+    }
+    lua_pop(L, 1);
+    // Stack: [mt]
+    lua_getfield(L, -1, "__methods");
+    // Stack: [mt, __methods]
+    lua_pushvalue(L, 2);
+    lua_gettable(L, -2);
+    return 1;
+}
+
+/*
+static int Lgc(lua_State *L)
+{
+    lua_getglobal(L, "print");
+    lua_pushstring(L, "===========> Garbage collection of ");
+    lua_getglobal(L, "tostring");
+    lua_pushvalue(L, 1);
+    lua_call(L, 1, 1);
+    lua_concat(L, 2);
+    lua_call(L, 1, 0);
+    return 0;
+}
+*/
+
+static const luaL_Reg R[] =
+{
+    { "__len", Llen},
+    //{ "__gc", Lgc},
+    //{ "__eq", Leq},
+    { "__index", Lindex},
+    //{ "__hash", Lhash},
+    { "new", Lcreate_instance},
+    { NULL, NULL}
+};
+
+static int Lmake_class(lua_State *L)
+{
+    // args: fields, [methods, [metamethods]]
+    int n_args = lua_gettop(L);
+
+    // CLS = {}
+    lua_newtable(L);
+    // Stack: [CLS]
+
+    // If metamethods were passed in, copy them over
+    if (n_args > 2) {
+        lua_pushnil(L);
+        // Stack: [CLS, nil]
+        while (lua_next(L, 3) != 0) {
+            lua_pushvalue(L, -2);
+            lua_pushvalue(L, -2);
+            // Stack: [CLS, method_name, method_value, method_name, method_value]
+            lua_settable(L, -5);
+            // Stack: [CLS, method_name, method_value]
+            lua_pop(L, 1);
+            // Stack: [CLS, method_name]
+        }
+    }
+
+    // CLS.__instances = {}
+    lua_newtable(L);
+    // Stack: [CLS, CLS.__instances]
+    lua_setfield(L, -2, "__instances");
+    // Stack: [CLS]
+
+    // CLS.__fields = arg1
+    lua_pushvalue(L, 1);
+    // Stack: [CLS, __fields]
+    lua_setfield(L, -2, "__fields");
+    // Stack: [CLS]
+
+    lua_newtable(L);
+    // Stack: [CLS, __methods]
+    // If methods were passed in, copy them over
+    if (n_args > 1) {
+        // Stack: [
+        lua_pushnil(L);
+        // Stack: [CLS, __methods, nil]
+        while (lua_next(L, 2) != 0) {
+            lua_pushvalue(L, -2);
+            lua_pushvalue(L, -2);
+            // Stack: [CLS, __methods, method_name, method_value, method_name, method_value]
+            lua_settable(L, -5);
+            // Stack: [CLS, __methods, method_name, method_value]
+            lua_pop(L, 1);
+            // Stack: [CLS, __methods, method_name]
+        }
+        // Stack: [CLS, __methods]
+    }
+    lua_setfield(L, -2, "__methods");
+    // Stack: [CLS]
+
+    // Populate __len, __eq, __index, new, etc.
+    luaL_register(L,NULL,R);
+
+    // setmetatable(CLS, {__new=CLS.new})
+    lua_createtable(L, 0, 1);
+    lua_pushcfunction(L, Lcreate_instance);
+    lua_setfield(L, -2, "__call");
+    lua_setmetatable(L, -2);
+    // Stack [CLS]
+
+    return 1;
+}
+
+LUALIB_API int luaopen_immutable(lua_State *L)
+{
+    lua_pushcfunction(L, Lmake_class);
+    return 1;
+}
diff --git a/test.lua b/test.lua
new file mode 100644
index 0000000..43f9796
--- /dev/null
+++ b/test.lua
@@ -0,0 +1,71 @@
+local immutable = require"immutable"
+
+local bright = string.char(27).."[1m"
+local blue = string.char(27).."[34m"
+local reset = string.char(27).."[0m"
+local function say(...) io.write(bright..blue); print(...); io.write(reset); end
+local function repr(t)
+    local tmp = {}
+    for k,v in pairs(t) do tmp[#tmp+1] = ("%s=%s"):format(k,v) end
+    return "{"..table.concat(tmp, ", ").."}"
+end
+
+local Vec = immutable({"x","y"}, {
+    len2=function(self)
+        return self.x*self.x + self.y*self.y
+    end,
+}, {
+    __add=function(self, other)
+        local cls = getmetatable(self)
+        return cls(self.x+other.x, self.y+other.y)
+    end,
+    __tostring=function(self)
+        return "Vec("..tostring(self.x)..", "..tostring(self.y)..")"
+    end,
+})
+
+local v = Vec(1,3)
+say(v)
+local also_v = Vec(1,3)
+say(also_v)
+-- Hash collision right now
+local not_v = Vec(true,3)
+say(not_v)
+local also_not_v = Vec(true,3)
+say(also_not_v)
+
+say(v == also_v)
+say(v + Vec(5,6))
+collectgarbage()
+say(Vec("hello", "world"))
+say(Vec("hello", "world"))
+collectgarbage()
+collectgarbage()
+
+say("Let's look at the instances")
+for h,b in pairs(Vec.__instances) do
+    say(("Hash bucket: 0x%x"):format(h))
+    for k,v in pairs(b) do
+        local tmp = {}
+        for kk,vv in pairs(v) do tmp[#tmp+1] = tostring(vv) end
+        say('    <'..table.concat(tmp, ", ")..'>')
+    end
+end
+
+local FooVec = immutable({"x","y"}, {
+    len2=function(self)
+        return self.x*self.x + self.y*self.y
+    end,
+}, {
+    __add=function(self, other)
+        local cls = getmetatable(self)
+        return cls(self.x+other.x, self.y+other.y)
+    end,
+    __tostring=function(self)
+        return "Vec("..tostring(self.x)..", "..tostring(self.y)..")"
+    end,
+})
+
+say("FooVec: "..tostring(FooVec(1,3)))
+say("FooVec == Vec: "..tostring(FooVec(1,3) == Vec(1,3)))
+say("FooVec:len2() = "..tostring(FooVec(1,3):len2()))