+httpVersionP = string "HTTP/"
+ >>
+ -- 頻出するので高速化
+ choice [ do string "1.0"
+ return $ HttpVersion 1 0
+ , do string "1.1"
+ return $ HttpVersion 1 1
+ -- 一般の場合
+ , do major <- many1 digit
+ char '.'
+ minor <- many1 digit
+ return $ HttpVersion (read major) (read minor)
+ ]