用惯用的F#方式将一个列表(n个元组或列表)与另一个列表(以及数组)缩放的方式是什么? [英] What would be an idiomatic F# way to scale a list of (n-tuples or list) with another list, also arrays?

问题描述

给出:

let weights = [0.5;0.4;0.3]
let X = [[2;3;4];[7;3;2];[5;3;6]]

我想要的是:
wX = [(0.5)*[2;3;4];(0.4)*[7;3;2];(0.3)*[5;3;6]]
我想知道一种使用列表以及数组的优雅方法.欢迎其他优化信息

what I want is:
wX = [(0.5)*[2;3;4];(0.4)*[7;3;2];(0.3)*[5;3;6]]
would like to know an elegant way to do this with lists as well as with arrays. Additional optimization information is welcome

推荐答案

您编写了一个列表列表，但是您的代码显示了一个元组列表.采取自由进行调整的解决方案将是

You write about a list of lists, but your code shows a list of tuples. Taking the liberty to adjust for that, a solution would be

let weights = [0.5;0.4;0.3]
let X = [[2;3;4];[7;3;2];[5;3;6]]
X
|> List.map2 (fun w x -> 
    x 
    |> List.map (fun xi -> 
        (float xi) * w
    )
) weights

根据您对语法的舒适程度，您可能更喜欢像oneliner这样的

Depending on how comfortable you are with the syntax, you may prefer a oneliner like

List.map2 (fun w x -> List.map (float >> (*) w) x) weights X

对于序列(Seq.map2，Seq.map)和数组(在Array模块中)，存在相同的库函数.

The same library functions exist for sequences (Seq.map2, Seq.map) and arrays (in the Array module).

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