string – 遍历包括空行的行

local s = "foo\nbar\n\njim"
for line in magiclines(s) do
  print( line=="" and "(blank)" or line)
end
--> foo
--> bar
--> (blank)
--> jim

此代码不包含空行：

for line in string.gmatch(s,'[^\r\n]+') do print(line) end
--> foo
--> bar
--> jim

此代码包含额外的虚假空白行：

for line in string.gmatch(s,"[^\r\n]*") do
  print( line=="" and "(blank)" or line)
end
--> foo
--> (blank)
--> bar
--> (blank)
--> (blank)
--> jim
--> (blank)

function magiclines(s)
        if s:sub(-1)~="\n" then s=s.."\n" end
        return s:gmatch("(.-)\n")
end