Thread: First Plugin attempt, decided to take errors to wiser heads than my own.

I want to eventually create a basic calculator that does operations like -*/+. Here's what I have so far. I'm trying to assign a chat command:

import "Turbine"

Turbine.Shell.WriteLine("Basic Calculator by Cerridan");
BasicCalc = class( Turbine.ShellCommand );
function BasicCalc:Execute( command, arguments )
if((arguments == nil) or (string.len(arguments) == 0)) then
Turbine.Shell.WriteLine("Inval id Arguments!");
end

--Assigning integers and symbols to separate arrays.
local ints = {};
local index = 1;
local symbols = {};

for word in arguments:gmatch( "%d+" ) do
ints[index] = word;
index = index + 1;
end

index = 1;

for word in arguments:gmatch( "%[/*%-+]" ) do
symbols[index] = word;
index = index + 1;
end
end

Calc = BasicCalc();
Turbine.Shell.AddCommand( "calc", BasicCalc );

When I run it though, I get:

"...BasicCalculator\Main.lua:3 : attempt to call global 'class' (a nil value)"

This may be the totally wrong way to assign a command but any help on it would be appreciated. I've got some Java experience, if anyone feels like explaining in terms of Java code.

Thanks!
Cerridan of Firefoot

You mean like http://www.lotrointerface.com/downlo...alculator.html?



The "class" definition is not imported with the default Turbine import (or any of the Turbine imports), and it is not a standard feature of lua. If you want to use classes (of course you do), you need to copy the "Class.lua" file from the Turbine Examples folder into your plugin (and you probably want "Type.lua" too) and import them in the right order (Class before Type iirc).

I think I fixed it. I put in

BasicCalc = Turbine.ShellCommand();

instead of the class() definition.

I'm aiming to make a calculator that you can run via a text command that doesn't require UI, ie (works at the time of writing):
/bc 20+3
would print out
20 + 3 = 23

Replace:

Code:

Calc = BasicCalc();
Turbine.Shell.AddCommand( "calc", BasicCalc );

with:

Code:

Calc = BasicCalc();
Turbine.Shell.AddCommand( "calc", Calc );

You need to pass AddCommand an instance of a command and not the command class itself.


This has the potential to get messy - it'll depend on how you approach it. Good luck.

Massive edit: Although this is technically a parsing problem, you don't have to really use the full set of parsing tools to do it. I think.

Code:

import "Turbine"

--[[
Currently supported commands
# represents positive numbers
# may be substituted for "ans"

#[/*-+^]#
[/*-+^]#
#[/*-+^]
--]]

--Version tracker
versionNum = "1.0.1"
--Warnings
warn = true;
warning = "!!This code does not support negative numbers!!";

--Make this a command to be executed each time command called
BasicCalc = Turbine.ShellCommand();

--Create Previous Answer Variable
prevValue = 1;

--What to do every time user types in chat command
function BasicCalc:Execute( command, arguments )

	--If user types in base command then print help
	if((arguments == nil) or (string.len(arguments) < 2)) then
		Turbine.Shell.WriteLine(self:GetHelp());
		return;
	end
	
	--Answer assumption cases - if the first char of the string is an operator
	--then append previous answer value to the front
	if(arguments:sub(1,1):match("[%^/*%-+x]")) then
		arguments = prevValue .. arguments;
	end
	--If the last char of the string is an operator then append to back
	if(arguments:sub(arguments:len(), arguments:len()):match("[%^/*%-+x]")) then
		arguments = arguments .. prevValue;
	end
	
	--Split by operators
	arr = self:Split(arguments, "[ +%-*/x%^]");
	
	--Kill invalid cases
	if(arr[1] == nil or arr[2] == nil) then
		Turbine.Shell.WriteLine("Arguments Invalid!");
		return;
	end
	
	--Get operator
	find = string.find(arguments, "[/*%-+x%^]");
	oper = string.sub(arguments, find, find);
	
	--If user entered "ans" for front, back, or both operators then replace with actual value.
	if(arr[1] == "ans") then
		arr[1] = prevValue;
	end
	if(arr[2] == "ans") then
		arr[2] = prevValue;
	end
	
	--If multiplication, replace with x to make it look nicer
	if(oper == "*") then oper = "x"; end
	
	--Result Variable
	out = 0;
	
	--Failure variable
	fail = false;
	
	--Operator Cases
	if(oper == "+") then	 out = arr[1] + arr[2];
	elseif(oper == "-") then	out = arr[1] - arr[2];
	elseif(oper == "x") then	out = arr[1] * arr[2];
	elseif(oper == "/") then	out = arr[1] / arr[2];
	elseif(oper == "^") then	out = math.pow(arr[1], arr[2]);
	else 
		fail = true;
		Turbine.Shell.WriteLine("Unrecognized Operator!");
	end
	--Write a line out with the equation input and the resultant number.
	if(fail == false)
		Turbine.Shell.WriteLine(arr[1] .. " " .. oper .. " " .. arr[2] .. " = " .. out);
		--Store answer in answer variable if not negative
		if(out >= 0) prevValue = out; end
	end	
end

--Get help strings.
function BasicCalc:GetHelp()
	return self:GetShortHelp() .. "\nCerridan's Calculator Plugin";
end

function BasicCalc:GetShortHelp()
	return "/bc | /calc [#|ans] [/*-+] [#|ans]";
end

--Split method, not written by me.
function BasicCalc:Split(str, delim, maxNb)
    -- Eliminate bad cases...
    if string.find(str, delim) == nil then
        return { str }
    end
    if maxNb == nil or maxNb < 1 then
        maxNb = 0    -- No limit
    end
    local result = {}
    local pat = "(.-)" .. delim .. "()"
    local nb = 0
    local lastPos
    for part, pos in string.gfind(str, pat) do
        nb = nb + 1
        result[nb] = part
        lastPos = pos
        if nb == maxNb then break end
    end
    -- Handle the last field
    if nb ~= maxNb then
        result[nb + 1] = string.sub(str, lastPos)
    end
    return result
end

--Text written on initialization
Turbine.Shell.WriteLine("Basic Calculator " .. versionNum .. " by Cerridan");
if(warn) then Turbine.Shell.WriteLine(warning); end
Turbine.Shell.WriteLine("Usage: /bc | /calc [#|ans] [/*-+] [#|ans]");

--Add commands so they can be called from the chatbox
Turbine.Shell.AddCommand( "calc", BasicCalc );
Turbine.Shell.AddCommand( "bc", BasicCalc );

That's what I have so far, planning to add square roots, and negative number support...

A couple of pointers.

First, you can combine the AddCommand lines so that you assign all aliases for the same command in one line by separating the aliases with a semi-colon:
Turbine.Shell.AddCommand( "calc;bc", BasicCalc );

Second, and really more important, you should remove any alias commands that you add. The most common means is to use an Unload event handler. Failure to remove commands can have undesirable results including crashing the client in certain circumstances. The simplest Unload event handler would be:
plugin.Unload = function()
Turbine.Shell.RemoveCommand( BasicCalc );
end

Third, you can access the version info from the .plugin file instead of using a separate variable by using:
Turbine.Shell.WriteLine( "Basic Calculator " .. plugin:GetVersion() .. " by Cerridan" );
so that you only have to update the version number in the .plugin file (and the .plugincompendium file if you want to be supported by Plugin Compendium).

Note that "plugin" is a special variable created by Turbine which is only valid during the initialization of your plugin - basically the time when your main plugin file is being parsed and executed - once the plugin is loaded, the "plugin" variable will no longer be accessible so don't reference it in event handlers, instead use Plugins["Calc"] (where "Calc" is the actual name of your plugin from the <name> tag of your .plugin file).

As a rule, anything you create, you should destroy before unloading. That includes commands, eventhandlers, etc. That will help minimize the chances of your plugin causing undesirable results.

Thanks for all the help!

The plugin thus far:

Code:

import "Turbine"

--[[
Currently supported commands
# represents positive numbers
# may be substituted for "ans"

#[/*-+^]#
[/*-+^]#
#[/*-+^]

# may not be substituted for ans in the below cases:
sqrt#
sin#
cos#
tan#
--]]

--Warnings
warn = true;
warning = "!!This code does not support negative numbers!!";

--Make this a command to be executed each time command called
BasicCalc = Turbine.ShellCommand();

--Create Previous Answer Variable
prevValue = 1;

--What to do every time user types in chat command
function BasicCalc:Execute( command, arguments )

	--If user types in base command then print help
	if((arguments == nil) or (string.len(arguments) < 2)) then
		Turbine.Shell.WriteLine(self:GetHelp());
		return;
	end
	
	--Check for special functions
	if(arguments:len() >=  5 and arguments:sub(1,4) == "sqrt")  then
		self:PrintResult(arguments:sub(5, arguments:len()), nil, "sqrt", math.sqrt(arguments:sub(5, arguments:len())));
		return;
	elseif(arguments:len() >= 4 and arguments:sub(1, 3) == "sin") then
		self:PrintResult(arguments:sub(4, arguments:len()), nil, "sin", math.sin(arguments:sub(4, arguments:len())));
		return;
	elseif(arguments:len() >= 4 and arguments:sub(1, 3) == "cos") then
		self:PrintResult(arguments:sub(4, arguments:len()), nil, "cos", math.cos(arguments:sub(4, arguments:len())));
		return;
	elseif(arguments:len() >= 4 and arguments:sub(1, 3) == "tan") then
		self:PrintResult(arguments:sub(4, arguments:len()), nil, "tan", math.tan(arguments:sub(4, arguments:len())));
		return;
	end
	
	
	--Answer assumption cases - if the first char of the string is an operator
	--then append previous answer value to the front
	if(arguments:sub(1,1):match("[%^/*%-+x]")) then
		arguments = prevValue .. arguments;
	end
	--If the last char of the string is an operator then append to back
	if(arguments:sub(arguments:len(), arguments:len()):match("[%^/*%-+x]")) then
		arguments = arguments .. prevValue;
	end
	
	--Split by operators
	arr = self:Split(arguments, "[ +%-*/x%^]");
	
	--Kill invalid cases
	if(arr[1] == nil or arr[2] == nil) then
		Turbine.Shell.WriteLine("Arguments Invalid!");
		return;
	end
	
	--Get operator
	find = string.find(arguments, "[/*%-+x%^]");
	oper = string.sub(arguments, find, find);
	
	--If user entered "ans" for front, back, or both operators then replace with actual value.
	if(arr[1] == "ans") then
		arr[1] = prevValue;
	end
	if(arr[2] == "ans") then
		arr[2] = prevValue;
	end
	
	--If multiplication, replace with x to make it look nicer
	if(oper == "*") then oper = "x"; end
	
	--Result Variable
	out = 0;
	
	--Failure variable
	fail = false;
	
	--Operator Cases
	if(oper == "+") then	 out = arr[1] + arr[2];
	elseif(oper == "-") then	out = arr[1] - arr[2];
	elseif(oper == "x") then	out = arr[1] * arr[2];
	elseif(oper == "/") then	out = arr[1] / arr[2];
	elseif(oper == "^") then	out = math.pow(arr[1], arr[2]);
	else 
		fail = true;
		Turbine.Shell.WriteLine("Unrecognized Operator!");
	end
	--Write a line out with the equation input and the resultant number.
	if(fail == false) then self:PrintResult(arr[1], arr[2], oper, out); end
end

function BasicCalc:PrintResult(one, two, oper, out)
	if(oper == "sqrt" or oper == "sin" or oper == "cos" or oper == "tan") then
		Turbine.Shell.WriteLine(oper .. "(" .. one .. ") = " .. out);
	else
		Turbine.Shell.WriteLine(arr[1] .. " " .. oper .. " " .. arr[2] .. " = " .. out);	
	end	
	--Store answer in answer variable if not negative
	if(out >= 0) then prevValue = out; end
end

--Get help strings.
function BasicCalc:GetHelp()
	return self:GetShortHelp() .. "\nCerridan's Calculator Plugin";
end

function BasicCalc:GetShortHelp()
	return "/bc | /calc [#|ans] [/*-+] [#|ans]";
end

--Split method, not written by me.
function BasicCalc:Split(str, delim, maxNb)
    -- Eliminate bad cases...
    if string.find(str, delim) == nil then
        return { str }
    end
    if maxNb == nil or maxNb < 1 then
        maxNb = 0    -- No limit
    end
    local result = {}
    local pat = "(.-)" .. delim .. "()"
    local nb = 0
    local lastPos
    for part, pos in string.gfind(str, pat) do
        nb = nb + 1
        result[nb] = part
        lastPos = pos
        if nb == maxNb then break end
    end
    -- Handle the last field
    if nb ~= maxNb then
        result[nb + 1] = string.sub(str, lastPos)
    end
    return result
end

--Unload handler
plugin.Unload = function()
Turbine.Shell.RemoveCommand(BasicCalc);
end

--Text written on initialization
Turbine.Shell.WriteLine("Basic Calculator " .. plugin:GetVersion() .. " by Cerridan");
if(warn) then Turbine.Shell.WriteLine(warning); end
Turbine.Shell.WriteLine("Usage: /bc | /calc [#|ans] [/*-+] [#|ans]");

--Add commands so they can be called from the chatbox
Turbine.Shell.AddCommand( "calc;bc", BasicCalc );

Hmm... had an odd thought and did some poking around. You may want to check out the loadstring function. Apparently, it's Lua's version of eval().