Loading strings for variable naming

local var = loadstring("return "..varname)()

local var = getfenv()[varname]

local loadstring(var) = "hello"

Doyle3694, on 14 December 2012 - 08:39 AM said:

Can I do

local loadstring(var) = "hello"

?

local varname = "blah"
loadstring("return "..varname)() = "hello"

local func = loadstring("return os.version")
local ver = func()	-- now ver holds a reference to the variable os.version
print(ver)
ver = 1     -- reassign a number to ver

local func = function() return os.version end
local ver = func()   -- now ver holds a reference to the variable os.version
print(ver)
ver = 1    -- reassign a number to ver

loadstring("return os.version")() = "hello"

getfenv()[varname] = "hello"

--table to hold variables with strings as names
local userVars={}

while true do
	print("enter blank to exit")
	write("variable name >")
	local name=read()
	if name=="" then
	   break
	end
	if userVars[name] then
		print("current value of '"..name.."' is "..userVars[name])
	end
	write("New value:")
	local val=read()
	userVars[name]=val
	print("value set.")
end

print("final values:")
for k,v in pairs(userVars) do
   print(k.."=\""..v.."\"")
end

function makeVar(name)
   return name
end
makeVar("lawl") = "herpaderp"

Doyle3694, on 14 December 2012 - 10:12 AM said:

Oh, would that make

function makeVar(name)
   return name
end
makeVar("lawl") = "herpaderp"

function makeVar(varname, var)
  getfenv()['varname']=var
end
makeVar("lawl","herpaderp")

function makeVar(varname, var)
  loadstring("return "..varname)() = var
end
makeVar("lawl","herpaderp")

Lyqyd, on 14 December 2012 - 11:11 AM said:

Your first example looks plausible, but your second looks approximately equivalent to the code you're disagreeing with.

loadstring("return "..varname)()

testVar = {"I am a table."}

local function getVar(varname)
  return loadstring("return "..varname)()
end
alias = getVar("testVar")
alias == testVar    -- True

testVar = {"I am a table."}

local function getVar(varname)
  return varname
end
alias = getVar("testVar")
alias == "testVar"    -- True

function varCheck(var, stan)
   if var == nil then					
     loadstring("return "..var)() = stan
   end						  
end									  

Doyle3694, on 21 December 2012 - 04:50 AM said:

OK Orwell, thanks ;)/> Can I get an explanation on getfenv() and it's uses?(Don't like using stuff I don't understand)

getfenv([f])
Returns the current environment in use by the function. f can be a Lua function or a number that specifies the function at that stack level: Level 1 is the function calling getfenv. If the given function is not a Lua function, or if f is 0, getfenv returns the global environment. The default for f is 1.

local tEnv = getfenv()  -- put the environment table for this function in tEnv
local printFunc = tEnv['print'] -- get the value for the key 'print' out of tEnv, it's a function pointer in this case
print( tostring( printFunc == print ) )  -- print the equality of the two function pointers
printFunc( tostring printFunc == print ) ) -- use the function pointer to call print
tEnv['print']("Test!") -- call the function pointer directly on the retreived env. table
getfenv()['print']("Test!") -- call the function pointer directly on the returned env. table from getfenv()

_G[string]=something

pcall(setfenv(function() code end,setmetatable({[string]=something},getfenv()))

PixelToast, on 21 December 2012 - 05:57 AM said:

you dont really want to use getfenv though
use
_G[string]=something

x = "test"
print( _G["x"] )

Orwell, on 21 December 2012 - 06:00 AM said:

-snip-
Won't work in the case of os.run as I mentioned earlier

PixelToast, on 21 December 2012 - 05:57 AM said:

pcall(setfenv(function() code end,setmetatable({[string]=something},getfenv()))

if you are worried about os.run

local G = getfenv()

function varCheck(var, stan)
   if var == nil then
	  getfenv()[var] = stan		  
   end							
end	

Doyle3694, on 21 December 2012 - 06:32 AM said:

OK, think I got it. will that make

function varCheck(var, stan)
   if var == nil then
	  getfenv()[var] = stan		  
   end							
end	

a working version?

function varCheck(varName, stan)
  getfenv()[varName] = getfenv()[varName] or stan
end	

Lyqyd, on 21 December 2012 - 06:36 AM said:

I very much doubt that nil is usable as an index.

ChunLing, on 21 December 2012 - 07:21 AM said:

You have to admit, you didn't explain that varName was the string matching var's identifier. Though you did call it varName…which…does that count as an explanation? I can't tell.