Re: Most efficient way to recognize a line by its first (up to) three characters

[Luiz Henrique de Figueiredo <lhf@...>]

>     local prefix, info = line:sub(1,3), line:sub(4)
>     if prefix == "abc" then
>       -- do something
>     elseif prefix == "123" then
>       -- do something else
>     elseif ...

Consider this scheme instead of a chain of ifs:

local handlers={
	["abc"]=function (prefix,info) ... end,
	["123"]=function (prefix,info) ... end,
}

local badprefix=function (prefix,info) error("cannot handle "..prefix) end

while true do
	local prefix, info = line:sub(1,3), line:sub(4)
	local h = handlers[prefix] or badprefix
	h(prefix,info)
end