function paramstr_to_flags(str)
	local function string_is_flag(str)
		return type(str)=="string" and str[1]=="-"
	end
	local function string_is_ok_arg(str)
		return type(str)!="string" or #str>0
	end
	local result={params={},flags={}}
	if(#str==0) return result
	local raw=split(str," ")
	local i=1
	while i<=#raw do
		local word=raw[i]
		if string_is_flag(word) then
			i+=1
			local args={}
			while i<=#raw and not string_is_flag(raw[i]) do
				if(string_is_ok_arg(raw[i]))add(args,raw[i])
				i+=1
			end
			result.flags[sub(word,2)]=args
		else
			if(string_is_ok_arg(word))add(result.params,word)
			i+=1
		end
	end
	return result
end