__SYMBOLS = { };
__DICT = { }; -- the keys will be strings (the commands), and values will be true
local function onAutoAssemble(script,syntax)
	local multiline_comment = false;
	for i = 0,script.count - 1 do
		local line = script[i];
		if multiline_comment then
			if line:find'}' then multiline_comment = false;
			end
		else
			if line:find'^registersymbol%(' then
				local command = 'un'..line:match'^registersymbol%(.-%)';
				if not __DICT[command] then -- the command isn't in the list yet
					__SYMBOLS[#__SYMBOLS + 1] = command;
					__DICT[command] = true; -- now it is
				end
			elseif line:find'^unregistersymbol%(' then
				local command = line:match'^unregistersymbol%(.-%)';
				__DICT[command] = nil; -- remove command from the list
				for i,v in ipairs(__SYMBOLS) do
					if v == command then
						table.remove(__SYMBOLS,i); -- also remove it from __SYMBOLS
						break;
					end
				end
			end
			if line:find'{' then
				multiline_comment = true;
			end
		end
	end
end
registerAutoAssemblerPrologue(onAutoAssemble);
local main = getMainForm();
local btn = createButton(main);
btn.width,btn.height,btn.top,btn.left = 100,30,290,460;
btn.caption = 'clear U-symbols';
btn.onClick = function()
	autoAssemble(table.concat(__SYMBOLS,'\n'));
	__SYMBOLS = { };
end