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P137 <* vs const的区别 #30
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可以呀,我们拿
|
很奇妙!清楚了一点。 |
[],Maybe作为Functor,Applicative,Monad,的实例,应该也有自己的实现。源代码怎么看? |
你先去hackage上查看base的文档(里面有源码的链接),自己推试试,不行我再来给你推个。 |
136页的定义 |
是的,确实不是简单的flip,effect的展开是有顺序的,感谢反馈。 |
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P137页第二段:
需要注意的是,很多新手会误认为(< * ) :: f a -> f b -> f a 和const函数一样,就直接忽略第二个参数。。。。。。。。。。。。。
Nothing <* Just 3
--Nothing
Just <* Nothing
--Nothing
[1..2] <* [1..10]
--[1111111111,2222222222]
能推导这个过程吗?为什么?
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