以非交互方式将函数参数传递给 Julia

问题描述

我在一个文件中有一个 Julia 函数.假设它是下面的.现在我想将参数传递给这个函数.我试过做

I have a Julia function in a file. Let's say it is the below. Now I want to pass arguments into this function. I tried doing

julia filename.jl randmatstat(5) 

但这会给出一个错误，即("令牌是意外的.不确定解决方案是什么.如果有一个主要功能/如何使用 Julia 编写完整的解决方案，我也有点担心.例如什么是 Julia 程序的起点/入口点吗?

but this gives an error that '(' token is unexpected. Not sure what the solution would be. I am also a little torn on if there is a main function / how to write a full solution using Julia. For example what is the starting / entry point of a Julia Program?

function randmatstat(t)
    n = 5
    v = zeros(t)
    w = zeros(t)
    for i = 1:t
        a = randn(n,n)
        b = randn(n,n)
        c = randn(n,n)
        d = randn(n,n)
        P = [a b c d]
        Q = [a b; c d]
        v[i] = trace((P.'*P)^4)
        w[i] = trace((Q.'*Q)^4)
    end
    std(v)/mean(v), std(w)/mean(w)
end

推荐答案

Julia 没有这样的入口点".当您从终端调用 julia myscript.jl 时，您实际上是在要求 julia 执行脚本并退出.因此，它需要是一个脚本.如果您的脚本中只有一个函数定义，那么除非您稍后从脚本中调用该函数，否则它不会做太多事情.

Julia doesn't have an "entry point" as such. When you call julia myscript.jl from the terminal, you're essentially asking julia to execute the script and exit. As such, it needs to be a script. If all you have in your script is a function definition, then it won't do much unless you later call that function from your script.

至于参数，如果你调用 julia myscript.jl 1 2 3 4，所有剩余的参数(即在本例中为 1、2、3 和 4)变成一个字符串数组特殊名称 ARGS.您可以使用此特殊变量来访问输入参数.

As for arguments, if you call julia myscript.jl 1 2 3 4, all the remaining arguments (i.e. in this case, 1, 2, 3 and 4) become an array of strings with the special name ARGS. You can use this special variable to access the input arguments.

例如如果你有一个简单的 julia 脚本:

e.g. if you have a julia script which simply says:

# in julia mytest.jl
show(ARGS)

然后从 linux 终端调用它会得到这样的结果:

Then calling this from the linux terminal will give this result:

<bashprompt> $ julia mytest.jl 1 two "three and four"
UTF8String["1","two","three and four"]

因此，根据我从您的程序中了解到的情况，您可能想做这样的事情(注意:在 julia 中，该函数需要在调用之前定义).

So, from what I understand from your program, you probably want to do something like this (note: in julia, the function needs to be defined before it's called).

# in file myscript.jl
function randmatstat(t)
    n = 5
    v = zeros(t)
    w = zeros(t)
    for i = 1:t
        a = randn(n,n)
        b = randn(n,n)
        c = randn(n,n)
        d = randn(n,n)
        P = [a b c d]
        Q = [a b; c d]
        v[i] = trace((P.'*P)^4)
        w[i] = trace((Q.'*Q)^4)
    end
    std(v)/mean(v), std(w)/mean(w)
end

t = parse(Int64, ARGS[1])
(a,b) = randmatstat(t)
print("a is $a, and b is $b
")

然后像这样从你的 linux 终端调用它:

And then call this from your linux terminal like so:

julia myscript.jl 5

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