将2个列表函数组合成1? [英] Combine 2 list functions into 1?
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问题描述
我如何结合以下两个函数:
replaceNth n newVal(x:xs)
pre>
| n == 0 = newVal:xs
|否则= x:replaceNth(n-1)newVal xs
replaceMthNth mnv arg = replaceNth m(replaceNth nv(arg !! m))arg
变成一个函数吗?
是否有可能?
replacemn
0(z:xs):xss)=(z:xs):xss
replacemn 0 nz((x:xs):xss)=
let(ys:yss)= replacemn 0 (x-ys):yss)
替换mnz(xs:xss)= xs:replacemn(m-1)nz xss
How would I combine the following 2 functions:
replaceNth n newVal (x:xs) | n == 0 = newVal:xs | otherwise = x:replaceNth (n-1) newVal xs replaceMthNth m n v arg = replaceNth m (replaceNth n v (arg !! m)) arg
into a single function?
Is it possible?
解决方案This is pretty hideous but it does the job:
replacemn 0 0 z ((x : xs) : xss) = (z : xs) : xss replacemn 0 n z ((x : xs) : xss) = let (ys : yss) = replacemn 0 (n-1) z (xs : xss) in ((x : ys) : yss) replacemn m n z (xs:xss) = xs : replacemn (m-1) n z xss
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