有什么理由只传递第一个元素而不传递整个数组？ [英] Any reason to pass just the first element instead of the whole array?

问题描述

好吧，所以昨天我有一个同事走进我的办公室，问我一个关于他必须使用的Fortran代码的问题。

Okay, so yesterday I had a co-worker coming into my office and asking me a question about Fortran code that he had to work with.

基本上，他使用的代码具有一个长的多维数组，并且一个子例程仅将这个长的多维数组作为参数。

Basically, the code that he works with has a long, multidimensional array, and a subroutine that expects just this long, multidimensional array as a parameter.

但是，仅调用该子例程的代码传递数组的第一个元素。代码仍然有效。所以他问我怎么可能。

However, the code calling that subroutine only passes the first element of the array. Yet the code works. So he asked me how that could be.

我还没有看到他的特定代码，但这是一个示例，说明了我如何理解这个问题（它确实有效！）：

I haven't seen his particular code, but here's an example how I understand the issue (and it works!):

subroutine print_array(a)
    implicit none
    integer :: a(10)
    write(*, *) a
end subroutine print_array

program passing
    implicit none
    integer :: i(10)
    i = (/ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 /)
    call print_array(i(1))
end program passing

所以我告诉他，Fortran顺序存储数组，并且数组的位置与第一个元素相同，并且由于子例程期望某种形状，

So I told him that Fortran stores arrays sequentially, and the location of the array is the same as to the first element, and since the subroutine expects a certain shape, it knows how far to read along this sequence, and so on.

我还告诉他这是不好的编程习惯，他不应该编写这种代码

I also told him that this was bad programming practice and that he shouldn't write this kind of code himself.

但是从那时起，我一直在想：为什么写这个的人为什么首先这样做？有什么理由吗？ （甚至不必是一个很好的理由。）

But since then I have been wondering: Why did whoever wrote this do it this way in the first place? Is there any reason to do that? (It doesn't even have to be a good reason.)

或者我是对的，这很愚蠢而且容易出错吗？

Or am I right and this is just silly and far too error-prone?

推荐答案

您对此的解释是正确的。您对遵循这种过时的做法的反感得到了广泛的支持。

Your explanation of how this works is correct. Your aversion to following this outdated practice is widely supported.

由于这个原因，我已经忘记了（尽管很久以前我曾经这么做过-就像从酒吧开车回家和抽烟一样，每个人都做过并且什么也没想到），但最早的语言版本可能不支持将整个数组作为参数传递。也许其他人的大脑没有被烈酒，烟草和FORTRAN的强力混合所吸引（没错，大声喊出来）。

As for the reason, I've forgotten (though long ago I used to do it to -- like driving home from the pub and smoking, everyone did and thought nothing of it) but perhaps the earliest versions of the language didn't support passing the whole array as a parameter. Perhaps someone else, whose brain is not addled by the potent mix of booze, tobacco and FORTRAN (that's right, shout it out) remembers more clearly.

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