Removing Text From A String

Hello there,

I am wanting to write a code that uses the ME bridge with the chat box that will let me pull items from my ME system by listening to chat. The problem I am having is that if you are not within a 64 block radius the chatbox can't use the tell function.( I'm on a SMP server) So the way I can see to solve this is to have the request and the item Id on the same line. So what I need to do is separate the calling command from the block ID within in variable is this possible?

You mean something like this?

local command, id = string.match(chatInput, "(%a+) (.*)")

Well the input would be somthing like !request 1 example. I need to take the!request out so the ME peripheral can pull out ID 1.

I suggest you to read the 'String Manipulation' chapter of the Lua 5.1 Reference Manual:
http://www.lua.org/manual/5.1/manual.html#5.4
Play around with the functions shown there and you should be able to come up with a solution to your problem.

Well firstly, if you wish to solve the range problem you can do 1 of 2 things.

1. If you have access to the SMP configs, bump up the range
2. Use OpenPeripheral, the terminal have unlimited range and can work cross-dimension too.

Now to the actual problem:

It is completely possible to parse a command and get the args from chat, firstly I would do this:


Using the method that Lyqyd posted we can extract the first word and the args like so

local cmd, args = chatInput:match("(%a+) (.+)")

Now this will actually parse all chat messages, which if not coded correctly, can become problematic with the computer. So we have it detect the ! at the start, if that doesn't exist, then it will return nil

local cmd, args = chatInput:match("!(%a+) (.+)")

if cmd then
  --# we now have a valid format of request through chat
end

Now we can also build a database of commands with a table like so

local commands = {
  ["request"] = doRequest,
  ["other"] = doOther,
  ["another"] = doAnother,
}

Now the format is the command (must be one word) is the key for the table and a function pointer as the value. A function pointer if you don't know is the address to the location in memory that a function is stored, so for example

function test()
  print("hello world")
end

is a function, and using `test` would get us the function pointer, using `print(test)` you can see this location in memory as "table: [location]" but we are straying from topic, so lets bring it back.

We then must define the function

local function doRequest( args )
  --# process the args and perform the request
end

now we should also check that the users command was actually a valid one, for this we do the following

if commands[cmd] then
  --# it was in the table, it is valid
else
  --# invalid command
end

So if we put together what we have so far we get the following

local function doRequest( args )
  --# process the args and perform the request
end


local commands = {
  ["request"] = doRequest,
}

local cmd, args = chatInput:match("!(%a+) (.+)")

if cmd then
  if commands[cmd] then
    commands[cmd]() --# call the function pointer, we have been given th
  else
    --# alert user that it was an invalid command
  end
--# no else here, it wasn't a command for us
end

As for in the `doRequest` function, there are several methods of attack, this is the one I like to use

local function doRequest(args)
  local qty, name = args:match("(%d+) (%a+)")
  if not (qty and name) then
    --# alert the user that they have mistyped the command and it must be "!request [qty] [name]"
    return
  end
  --# valid command, process the request here
end

Now all you need to do is put the process of gathering and processing the command into a loop, actually listen for the command, and you're set to having a program that can respond to commands.

A great tutorial on Patterns in Lua and how they work can be found in the Tutorials section and also the PIL.