例如，假设我想读一行并且还按一下铃铛：
λ getLine >> putChar '\007'
How lang and dreary is the night when I am frae my Dearie.
-- Blip and `()`. The line is lost.
λ getLine >>= (\x -> putChar '\007' >> return x
I restless lie frae e'en to morn though I were ne'er sae weary.
"I restless lie frae e'en to morn though I were ne'er sae weary."
-- A line and also a blip side effect.
这个想法似乎与const有很多共同点，唯一的区别是，即使仅保留第一个操作的值，给出的值也是有效的，并且都可以执行。 （与>>不同，后者保留第二个值。）我的意思是：
λ constM a b = a >>= \x -> b >> return x
这是一个更复杂的示例，涉及来自Text.ParserCombinators.ReadP的解析器：
λ readP_to_S (many1 (munch1 (not . isSpace) `constM` skipSpaces ) `constM` eof) <$> getLine
How slow ye move, ye heavy hours.
[(["How","slow","ye","move,","ye","heavy","hours."],"")]
我想知道此功能在base中是否可用，或者可以从base中的其他功能轻松构造。