Advanced Detection of Color (Works on all versions)

function advIsColor()
	local booColor = false -- Create variable local to only the function
	if term.isColor ~= nil then -- Test to see if term.isColor even exists within ComputerCraft
		booColor = term.isColor() -- If it is then set the booColor to either true or false
		if booColor == false then
			print("Colors Disabled") -- This will trigger if on a Stone Computer of the latest version
		else
			print("Colors Initialized.) -- This will trigger if on a Advanced Computer of the latest version
		end
	else
		print("Colors Disabled, Older Ver CC") -- This will trigger if on an older version of ComputerCraft
	end
	return booColor -- Function returns result to the program
end

-- Puts result into a variable
local verColor = advIsColor()

-- Repeat this, as needed, right before more text or terminal clears. Change the colors as well
if verColor == true then term.setTextColor(colors.black) term.setBackgroundColor(colors.lightBlue) end

-- The Programs Code
print("Are my Colors Different?")

local verColor = (term.isColor or false) and term.isColor()
if verColor == true then term.setTextColor(colors.black) term.setBackgroundColor(colors.lightBlue) end
print("Code/Text of Program")

TheOriginalBIT, on 15 December 2012 - 02:43 AM said:

Good job :)/> EDIT: I never thought of doing multi-os compatibility in this way.

FYI: This technique uses what is called function pointers, they are very neat. I discovered them once with the following code

Spoiler

currX, currY, currZ = 0, 0, 0
-- lots of stuff moving turtle around
function goToY(y)
  dirFunc
  if (y > currY) then
	 dirFunc = turtle.down
  elseif (y < currY) then
	 dirFunc = turtle.up
  else
	 return
  end
  while (currY ~= y) do
	 dirFunc()
  end
end

TrinaryAtom, on 15 December 2012 - 02:50 AM said:

TheOriginalBIT, on 15 December 2012 - 02:43 AM said:

Good job :)/> EDIT: I never thought of doing multi-os compatibility in this way.

FYI: This technique uses what is called function pointers, they are very neat. I discovered them once with the following code

Spoiler

currX, currY, currZ = 0, 0, 0
-- lots of stuff moving turtle around
function goToY(y)
  dirFunc
  if (y > currY) then
	 dirFunc = turtle.down
  elseif (y < currY) then
	 dirFunc = turtle.up
  else
	 return
  end
  while (currY ~= y) do
	 dirFunc()
  end
end

Thanks :)/>
and
Woah.. umm… i cant seem to follow what you did there. As soon as i think i get it, it totally looses me. >< But I think i understand what you were trying to show me.

dirFunc = turtle.up

function goToY(y)
  while (currY ~= y) do
    if (y > currY) then
      turtle.down()
    elseif (y < currY) then
      turtle.up()
    end
  end
end

TheOriginalBIT, on 15 December 2012 - 03:13 AM said:

If you wish to read my attempt at explaining how function pointers work and what I did in that example read the spoiler below :)/>

Spoiler

Basically what it does is this.

A function can be seen as a set of instructions in memory. A pointer 'points' ( :o/> WHAT?! :P/> ) to this location in memory. If you were to use print(turtle.up) it would print some hexadecimal number if that function exists, nil if it doesn't. So by doing

dirFunc = turtle.up

we are actually assigning the pointer to the turtle.up function to our variable dirFunc. Then when it comes to wanting to execute this function thats where you add ( ) (in lua, other languages are different ) to the end of the variable. This tells the compiler/runtime env (depending on the language) that you want to call the function that it points to.

So what my little code snippet did was it moved the turtle back to its origin y position. If the turtle was above the origin it would move it down, if it was below the origin it would move it up.

However using function pointers in the example I gave is kinda pointless. The code below is obviously a little smaller, and easier for most to understand, but function pointers can be used for some interesting purposes, case and point, your multi-os programs.

Alt method of doing the same thing:

Spoiler

function goToY(y)
  while (currY ~= y) do
	if (y > currY) then
	  turtle.down()
	elseif (y < currY) then
	  turtle.up()
	end
  end
end

TrinaryAtom, on 15 December 2012 - 03:20 AM said:

TheOriginalBIT, on 15 December 2012 - 03:13 AM said:

If you wish to read my attempt at explaining how function pointers work and what I did in that example read the spoiler below :)/>

Spoiler

Basically what it does is this.

A function can be seen as a set of instructions in memory. A pointer 'points' ( :o/> WHAT?! :P/> ) to this location in memory. If you were to use print(turtle.up) it would print some hexadecimal number if that function exists, nil if it doesn't. So by doing

dirFunc = turtle.up

we are actually assigning the pointer to the turtle.up function to our variable dirFunc. Then when it comes to wanting to execute this function thats where you add ( ) (in lua, other languages are different ) to the end of the variable. This tells the compiler/runtime env (depending on the language) that you want to call the function that it points to.

So what my little code snippet did was it moved the turtle back to its origin y position. If the turtle was above the origin it would move it down, if it was below the origin it would move it up.

However using function pointers in the example I gave is kinda pointless. The code below is obviously a little smaller, and easier for most to understand, but function pointers can be used for some interesting purposes, case and point, your multi-os programs.

Alt method of doing the same thing:

Spoiler

function goToY(y)
  while (currY ~= y) do
	if (y > currY) then
	  turtle.down()
	elseif (y < currY) then
	  turtle.up()
	end
  end
end

Excellent Read. I completely understand. Thanks :D/>

TheOriginalBIT said:

You should rep me up ;)/>/>

tiin57, on 15 December 2012 - 05:09 AM said:

TheOriginalBIT said:

You should rep me up ;)/>/>

Asking for rep is bad manners and will in the long run earn you less.

TrinaryAtom, on 15 December 2012 - 01:28 PM said:

I see a green arrow on there post. ( bottom right corner)

function advIsColor()
    return term.isColor and term.isColor()
end

immibis, on 15 December 2012 - 01:49 PM said:

function advIsColor()
	return term.isColor and term.isColor()
end

TheOriginalBIT, on 15 December 2012 - 01:55 PM said:

immibis, on 15 December 2012 - 01:49 PM said:

function advIsColor()
	return term.isColor and term.isColor()
end

Doesn't exactly print like his does ;)/> :P/>

immibis, on 15 December 2012 - 01:49 PM said:

function advIsColor()
	return term.isColor and term.isColor()
end

KillaVanilla, on 15 December 2012 - 02:14 PM said:

immibis, on 15 December 2012 - 01:49 PM said:

function advIsColor()
	return term.isColor and term.isColor()
end

I always assumed that that snippit would crash on older systems with an "attempt to call nil" error, but I realized that Lua would find that term.isColor would equal nil and immediately return false.

In any case, this "program" (it's more of a snippet, actually) is just an overly fancy and complex way to avoid errors while calling functions, so I'm not going to use it myself.

Also, I'm back from my hiatus, so…Hello again?

immibis, on 15 December 2012 - 01:57 PM said:

TheOriginalBIT, on 15 December 2012 - 01:55 PM said:

immibis, on 15 December 2012 - 01:49 PM said:

function advIsColor()
	return term.isColor and term.isColor()
end

Doesn't exactly print like his does ;)/> :P/>

Why would you want it to print?

KillaVanilla, on 15 December 2012 - 02:14 PM said:

immibis, on 15 December 2012 - 01:49 PM said:

function advIsColor()
	return term.isColor and term.isColor()
end

I always assumed that that snippit would crash on older systems with an "attempt to call nil" error, but I realized that Lua would find that term.isColor would equal nil and immediately return false.

immibis, on 15 December 2012 - 02:28 PM said:

-snip-

It returns nil, actually.

KillaVanilla, on 15 December 2012 - 03:03 PM said:

immibis, on 15 December 2012 - 02:28 PM said:

-snip-

It returns nil, actually.

…Odd. I wonder why; I assumed that it would return false because it was part of an AND statement.

local verColor = (term.isColor and term.isColor())
if verColor == true then term.setTextColor(colors.black) term.setBackgroundColor(colors.lightBlue) end
print("Code/Text of Program")

TheOriginalBIT, on 15 December 2012 - 03:41 PM said:

i believe that 'and' actually works as a ternary operator :)/>/>/>

TrinaryAtom, on 15 December 2012 - 04:05 PM said:

So with all that said, this is me "showing you up" with no explination.

local verColor = (term.isColor and term.isColor())
if verColor == true then term.setTextColor(colors.black) term.setBackgroundColor(colors.lightBlue) end
print("Code/Text of Program")

TrinaryAtom, on 15 December 2012 - 04:05 PM said:

I'm still learning here, but, i thought "and" could only be used with things like "if".
(To clarify, i have no idea what ternary operator is and this is more of a question.)

return term.isColor and term.isColor()

if term.isColor == false or term.isColor == nil then -- this line is equivalent to "if not term.isColor then"
   return term.isColor
else
   return term.isColor()
end

function advIsColor()
   return term.isColor and term.isColor()
end

-- This won't work if term.isColor doesn't exist, since advIsColor will return nil, which is not equal to false.
if advIsColor() == false then print("Not colour") end

-- All of these will work
if advIsColor() ~= true then print("Not colour") end
if advIsColor() then print("Colour") end
if not advIsColor() then print("Not colour") end

function advIsColor()
  return (term.isColor or false) and term.isColor()
end
function advIsColor()
  return (term.isColor and term.isColor()) or false
end

function advIsColor()
  local temp
  -- the "or" part. I save the result in temp to save repeating this part twice.
  if term.isColor ~= false and term.isColor ~= nil then -- again, this can be abbreviated as just "if term.isColor then"
	temp = term.isColor
  else
	temp = false
  end

  -- Now temp is either false, or term.isColor

  -- the "and" part
  if temp == false or temp == nil then
	-- Temp can't be nil, because it was either false or term.isColor, so it must be false
	return temp
  else
	return term.isColor()
  end
end

if X then
  return Y
else
  return Z
end

return (X ? Y : Z)

immibis, on 15 December 2012 - 09:00 PM said:

I'm not sure how that's "showing me up," whatever that means, because it's just my code inlined (taken out of a function and inserted directly, in place of the function call)

immibis, on 15 December 2012 - 09:00 PM said:

function advIsColor()
  return (term.isColor or false) and term.isColor()
end

immibis, on 15 December 2012 - 09:00 PM said:

function advIsColor()
  local temp
  -- the "or" part. I save the result in temp to save repeating this part twice.
  if term.isColor ~= false and term.isColor ~= nil then -- again, this can be abbreviated as just "if term.isColor then"
		temp = term.isColor
  else
		temp = false
  end

  -- Now temp is either false, or term.isColor

  -- the "and" part
  if temp == false or temp == nil then
		-- Temp can't be nil, because it was either false or term.isColor, so it must be false
		return temp
  else
		return term.isColor()
  end
end

local verColor = (term.isColor or false) and term.isColor()

function animUI(varColor, varb, varb)
   if varColor == true then term.setBackgroundColor(color.green) end
   Code
   Code
   Text
   Code
end

function random(varColor)
  Code
  Code
end

animUI(verColor, blah, blah)
random(verColor)