From 0f15ee34d78ae45e9ccd03b124993248bff30add Mon Sep 17 00:00:00 2001
From: Bruce Hill <bitbucket@bruce-hill.com>
Date: Fri, 9 Feb 2018 16:46:33 -0800
Subject: [PATCH] Added default tostring.

---
 limmutable.c | 81 ++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 69 insertions(+), 12 deletions(-)

diff --git a/limmutable.c b/limmutable.c
index b257481..deff4c0 100644
--- a/limmutable.c
+++ b/limmutable.c
@@ -1,6 +1,16 @@
 /*
 * immutable.c
-* An immutable table library.
+* An immutable table library by Bruce Hill. This library returns a single function
+* that can be used to declare immutable classes, like so:
+*
+*     immutable = require 'immutable'
+*     local Foo = immutable({"baz","qux"})
+*     local foo = Foo("hello", 99)
+*     assert(not pcall(function() foo.x = 'mutable' end))
+*     local t = {[foo]="it works"}
+*     assert(t[Foo("hello", 99)] == "it works")
+* 
+* Instances *are* garbage collected.
 */
 
 #include "lua.h"
@@ -199,14 +209,62 @@ static int Lindex(lua_State *L)
     }
     lua_pop(L, 1);
     // Stack: [mt]
-    lua_getfield(L, -1, "__methods");
-    // Stack: [mt, __methods]
     lua_pushvalue(L, 2);
-    // Stack: [mt, __methods, key]
+    // Stack: [mt, key]
     lua_gettable(L, -2);
     return 1;
 }
 
+static int Ltostring(lua_State *L)
+{
+    luaL_Buffer b;
+    luaL_buffinit(L, &b);
+
+    lua_getmetatable(L, 1);
+    // Stack: [mt]
+    
+    lua_getfield(L, -1, "name");
+    if (!lua_isnil(L, -1)) {
+        luaL_addvalue(&b);
+    } else {
+        lua_pop(L, 1);
+    }
+    luaL_addstring(&b, "(");
+    
+    lua_getfield(L, -1, "__instances");
+    // Stack: [mt, buckets]
+    lua_rawgeti(L, -1, *((lua_Integer*)lua_touserdata(L, 1)));
+    // Stack: [mt, buckets, bucket]
+    lua_pushvalue(L, 1);
+    // Stack: [mt, buckets, bucket, inst_udata]
+    lua_rawget(L, -2);
+    // Stack: [mt, buckets, bucket, inst_table]
+    
+    lua_getfield(L, -4, "__fields");
+    // Stack: [mt, buckets, bucket, inst_table, fields]
+    
+    lua_pushnil(L);
+    int needs_comma = 0;
+    while (lua_next(L, -2) != 0) {
+        // Stack: [mt, buckets, bucket, inst_table, fields, i, fieldname]
+        if (needs_comma) {
+            luaL_addstring(&b, ", ");
+        } else {
+            needs_comma = 1;
+        }
+        luaL_addvalue(&b);
+        // Stack: [mt, buckets, bucket, inst_table, fields, i]
+        luaL_addstring(&b, "=");
+        lua_rawgeti(L, -3, lua_tonumber(L, -1));
+        // Stack: [mt, buckets, bucket, inst_table, fields, i, value]
+        luaL_addvalue(&b);
+        // Stack: [mt, buckets, bucket, inst_table, fields, i]
+    }
+    luaL_addstring(&b, ")");
+    luaL_pushresult(&b);
+    return 1;
+}
+
 static const luaL_Reg R[] =
 {
     { "__len", Llen},
@@ -223,6 +281,8 @@ static int Lmake_class(lua_State *L)
     // CLS = {}
     lua_newtable(L);
     // Stack: [CLS]
+    lua_pushcfunction(L, Ltostring);
+    lua_setfield(L, -2, "__tostring");
 
     // If metamethods were passed in, copy them over
     if (n_args > 2) {
@@ -252,25 +312,22 @@ static int Lmake_class(lua_State *L)
     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]
+        // Stack: [CLS, nil]
         while (lua_next(L, 2) != 0) {
+            // Stack: [CLS, method_name, method_value]
             lua_pushvalue(L, -2);
             lua_pushvalue(L, -2);
-            // Stack: [CLS, __methods, method_name, method_value, method_name, method_value]
+            // Stack: [CLS, method_name, method_value, method_name, method_value]
             lua_settable(L, -5);
-            // Stack: [CLS, __methods, method_name, method_value]
+            // Stack: [CLS, method_name, method_value]
             lua_pop(L, 1);
-            // Stack: [CLS, __methods, method_name]
+            // Stack: [CLS, method_name]
         }
-        // Stack: [CLS, __methods]
     }
-    lua_setfield(L, -2, "__methods");
     // Stack: [CLS]
 
     // Populate __len, __eq, __index, new, etc.