Trouble getting started with Lua

Posted by BishopOsiris on Sat 26 Nov 2016 02:35 PM — 8 posts, 34,241 views.

BishopOsiris USA Sat 26 Nov 2016 02:35 PM #0

I bought the book "Programming in Lua" fourth edition by Lerusalimschy. I downloaded a binary interpreter for Window x86 from http://luadist.org/. When I open it, it says its a compiler. I can't even get the very first program (hello world) to work. It just says "nil". I was really excited to get started with this language but I hit this road block right out of the gate :(

Is there is a difference between a compiler and an interpreter?

What am I doing wrong?

Fiendish USA Global Moderator Sat 26 Nov 2016 09:24 PM #1

Quote:
I can't even get the very first program (hello world) to work. It just says "nil".

You've failed to tell us what you did so we have no comments on why it didn't work.

Nick Gammon Australia Forum Administrator Sun 27 Nov 2016 12:39 AM #2

You can use the Immediate window inside MUSHclient (Ctrl+I) to try a lot of Lua stuff. A possible problem is that if you go into an infinite loop you will have to force-quit MUSHclient. You can add this timer to pretty-much prevent that:


<timers>
  <timer name="runaway" 
    enabled="y" 
    second="5.00" 
    send_to="12"
    active_closed="y" >
  <send>

runaway_instruction_limit = 100000

function hook ()
  debug.sethook (hook, "", runaway_instruction_limit)
  error ("Runaway instruction limit reached")
end -- hook

debug.sethook (hook, "", runaway_instruction_limit)

</send>

  </timer>
</timers>

For advice on how to copy the above, and paste it into MUSHclient, please see Pasting XML.

As for your issue, copy/paste exactly what you tried, that printed "nil".

BishopOsiris USA Sun 27 Nov 2016 12:43 PM #3

How do I post images?

Fiendish USA Global Moderator Sun 27 Nov 2016 09:57 PM #4

Post them on an image sharing service and put the URL here.

Nick Gammon Australia Forum Administrator Sun 27 Nov 2016 10:02 PM #5

Why do you want to post an image? Copy and paste the code you were using, and copy and paste the error message you got.

To make your code more readable please use [code] tags as described here.

BishopOsiris USA Wed 07 Dec 2016 03:47 PM #6

At the Lua prompt in my interpreter:

Lua>

I type:

Quote:
hello.lua

This is what it spits out:


stdin:1 attempt to index a nil value (global 'hello')
stack traceback:
     stdin:1: in main chunk
     [C]: in ?

The hello.lua file is in the same directory as the interpreter and it consists of this:

 print("hello world")

Nick Gammon Australia Forum Administrator Wed 07 Dec 2016 10:10 PM #7

If you want to run an external file, then run Lua with an argument, eg.


lua hello.lua

You don't start Lua up, and then type in a file name like you did.

However if you have already started the Lua interpreter up, then you can "dofile" it, eg. from inside Lua:


Lua>  dofile "test.lua"