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Haskell笔记 (19)—— Guard

Posted by nanxiao on 二月 22, 2016 in Haskell笔记 |

guard跟在函数名和参数之后,用管道符号表示:

myCompare :: (Ord a) => a -> a -> Ordering  

myCompare a b
    | a < b = LT
    | a == b = EQ
    | otherwise = GT    

guard长得和pattern类似,pattern检查输入是否符合这个pattern,而guard则会计算布尔表达式,返回TrueFalse。如果返回值是True,则执行等号后面的函数体部分。

参考资料:
Guards, guards!

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