Programming Assistance Needed For C.C. Noob-In-Training

Hi guys.

I've been playing around with ComputerCraft and trying my best to learn lua, but I've encountered a problem with a program I have been trying to write.

Basically, me and my friend were building a train line. At either end of the platform there is a detector track hooked up to a computer, which has a monitor on top of it. I'm trying to make a program that will display a message on the monitor when one detector is triggered and a different message when the second is triggered.

Here is what I've come up with:

[attachment=432:TrainDetector.txt]

The issue i'm having is that the computer expects an "=" on line 2. Any additional issues I am currently unaware of, however I came to the forums to ask all of you pros:

a) what i've done wrong and
:)/>/> if there is a better way of doing it than the way I am…

I know i'm not amazing, but I won't learn anything if I don't ask!

Thank you all for reading my shout out for help!

original code:

if redstone.getInput("right") == "true" then
	    monitor top print("The Train has entered the Station!")
if redstone.getInput("left") == "true" then
	    monitor top print("The Train has left the Station!")
else
sleep(1)
end

Hello developer, I found (i am sorry to say) lots of mistakes:

1. It is true not "true" . Othewise Lua thinks you are talking about a string
2. When using if for the second time on the same level, use 'elseif'
3. The monitor isnt initialised, and used completely wrong. I would recommend for beginners to FIRST print it on the terminal screen, and if the code works, THEN print it on the monitor.
4. I put 'while true do' and 'end' around your code. This makes the program repeat, and not just check the redstone once.
5. I put the sleep after the program. You also need to sleep if the program detects a cart, not only when it doesnt detect.
6. I made the sleep last 0.1 seconds. I dont know exactly how long a detector pulses, but this way you are sure it doesnt miss the cart.


Changed code

while true do
if redstone.getInput("right") == true then
  print("The Train has entered the Station!")
elseif redstone.getInput("left") == true then
  print("The Train has left the Station!")
end
sleep(0.1)
end

Please note the adapted version is a little spammy :)/>/> but I tested it and it works.
Tomorrow I add the monitor version if you like.

there were some structuring error that I fixed but I can't get the monitors to work, here is what i got anyway, sorry :)/>/>

while true do
	if redstone.getInput("right") then
		monitor top print("The Train has entered the Station!")

	elseif redstone.getInput("left") then
		monitor top print("The Train has left the Station!")

end
end

Jan, on 02 September 2012 - 12:06 AM said:

original code:

if redstone.getInput("right") == "true" then
		monitor top print("The Train has entered the Station!")
if redstone.getInput("left") == "true" then
		monitor top print("The Train has left the Station!")
else
sleep(1)
end

Hello developer, I found (i am sorry to say) lots of mistakes:

1. It is true not "true" . Othewise Lua thinks you are talking about a string
2. When using if for the second time on the same level, use 'elseif'
3. The monitor isnt initialised, and used completely wrong. I would recommend for beginners to FIRST print it on the terminal screen, and if the code works, THEN print it on the monitor.
4. I put 'while true do' and 'end' around your code. This makes the program repeat, and not just check the redstone once.
5. I put the sleep after the program. You also need to sleep if the program detects a cart, not only when it doesnt detect.
6. I made the sleep last 0.1 seconds. I dont know exactly how long a detector pulses, but this way you are sure it doesnt miss the cart.


Changed code

while true do
if redstone.getInput("right") == true then
  print("The Train has entered the Station!")
elseif redstone.getInput("left") == true then
  print("The Train has left the Station!")
end
sleep(0.1)
end

Please note the adapted version is a little spammy :)/>/> but I tested it and it works.
Tomorrow I add the monitor version if you like.

Thank you for your help!!

I really appreciate all your crit. Thats why the forums are here after all lol,

Adding a monitor would be a nice learning curve. Me and my friend are both noob with cc, but i'm making an effort to learn lua.
Glad to see I didn't get a "you suck at lua" response though lol. Being a noob sucks lol

Cheers mates!

Its better to use os.pullEvent instead of a busy wait

  while true do
    os.pullEvent("redstone")
    if rs.getInput("left") then
       print("The train has left the station")
    else
       print("The train has entered the station")
    end
end

Ok I'll show you how to implement monitor

monitor = peripheral.wrap("top")

This will make a 'monitor' table, with functions

function say(text)
monitor.clear()
monitor.setCursorPos(1,1)
monitor.write(text)
end

This defines a simple function. The name of the function is 'say' and the argument will be saved as 'text'
It calls a function to clear the screen, then one to reset the cursor position, and finally 'writes' the gives text

while true do
os.pullEvent("redstone")
if redstone.getInput("right") == true then
  say("The Train has entered the Station!")
  sleep(3)
  say("...")
elseif redstone.getInput("left") == true then
  say("The Train has left the Station!")
  sleep(3)
  say("...")
end
end

In the main loop I replaced the print functions with the new say function
also I let the text stay on the screen for 3 seconds, and then clear the screen
Also I added Magus suggestion:
the os.pullEvent function waits until it 'something happens' (such as a key press, or redstone change) which is called an event.
Using os.pullEvent("redstone") waits for redstone events

Good luck programming

Full code:

monitor = peripheral.wrap("top")
function say(text)
monitor.clear()
monitor.setCursorPos(1,1)
monitor.write(text)
end
while true do
os.pullEvent("redstone")
if redstone.getInput("right") == true then
  say("The Train has entered the Station!")
  sleep(3)
  say("...")
elseif redstone.getInput("left") == true then
  say("The Train has left the Station!")
  sleep(3)
  say("...")
end
end