initial release

cosmic rage/lua/copytable.lua

@@ -0,0 +1,89 @@
+-- copytable.lua
+
+--[[
+
+Table copying functions. 
+
+See: http://www.gammon.com.au/forum/?id=8042
+
+Ideas by Shaun Biggs, David Haley, Nick Gammon
+
+Date: 21st July 2007
+
+This is intended to copy tables (make a real copy, rather than just the table
+reference).
+
+You can do a deep or shallow copy.
+
+Shallow: Simply copies the keys and values. 
+If a value is a table, you will get the same table as in the original.
+
+Deep: Copies keys and values recursively.
+If a value is a table, makes a copy of that table, and so on.
+
+Deep copy based on: http://lua-users.org/wiki/CopyTable
+
+Restrictions: Items must be "safe" to copy (eg. not file IO userdata). 
+
+The deep copied tables share the same metatable as the original ones. 
+To change this, change the line:
+
+   return setmetatable(new_table, getmetatable(object))
+
+to:
+
+   return setmetatable(new_table, _copy (getmetatable(object))
+
+Example:
+
+t1 = {
+  m = { a = 1, b = 2 },
+  n = { c = 3, d = 4 },
+  }
+
+require "copytable"  -- load this file
+
+t2 = copytable.shallow (t1)  -- shallow copy
+t3 = copytable.deep (t1)  -- copies sub tables as well
+
+--]]
+
+module (..., package.seeall)
+
+                     
+function deep (object)
+  local lookup_table = {}
+
+  local function _copy (object)
+    if type (object) ~= "table" then
+      return object
+    elseif lookup_table [object] then
+      return lookup_table [object]
+    end  -- if
+
+    local new_table = {}
+    lookup_table [object] = new_table
+
+    for index, value in pairs (object) do
+      new_table [_copy (index)] = _copy (value)
+    end  -- for
+
+    return setmetatable (new_table, getmetatable (object))
+  end  -- function _copy
+
+  return _copy (object)
+end  -- function deepcopy
+
+function shallow (t)
+  assert (type (t) == "table", "You must specify a table to copy")
+    
+  local result = {}
+
+  for k, v in pairs (t) do
+    result [k] = v
+  end -- for each table element
+
+  -- copy the metatable
+  return setmetatable (result, getmetatable (t))
+
+end  -- function shallow