gistfile1.lua

local function isLeader(u)
	return ((UnitInParty(u) or UnitInRaid(u)) and UnitIsPartyLeader(u))
end

local function isMasterLoot(u)
	local method, party, raid = GetLootMethod()
	local unit
	if method == 'master' then
		if party then
			unit = party == 0 and 'player' or 'party' .. party
		elseif raid then
			unit = 'raid' .. raid
		end
		return unit and UnitIsUnit(u, unit)
	end
end

local function func(unit)
	if isLeader(unit) and isMasterLoot(unit) then
		-- blah blah blah
	end
end