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haskell accumArray用法及代码示例


Haskell语言Array模块中函数accumArray的用法及代码示例。

用法类型:

Ix a => (b -> c -> b) -> b -> (a,a) -> [(a,c)] -> Array a b

通过使用将具有相同索引的关联值组合在一起的累加函数,放宽了给定索引最多只能在关联列表中出现一次的限制。第一个论点accumArray是累加函数;第二个是初始值;其余两个参数是一个边界对和一个关联列表,与数组函数一样。

示例1:

输入:
accumArray (+) 0 (1,3) [(1,2),(1,4),(2,1),(2,2),(2,3),(3,5)]
         
输出:
array (1,3) [(1,6),(2,6),(3,5)]
         

示例2:

输入:
accumArray (++) "" (1,3) [(1,"H"),(3,"y"),(1,"i"),(2,","),(3,"ou")]
         
输出:
array (1,3) [(1,"Hi"),(2,","),(3,"you")]
         

示例3:

输入:
accumArray (\x y-> x ++ y ++ "-") "XXX:" (1,3) [(1,"H"),(3,"y"),(1,"i"),(2,","),(3,"ou")]
         
输出:
array (1,3) [(1,"XXX:H-i-"),(2,"XXX:,-"),(3,"XXX:y-ou-")]
         

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