通过引用传递参数传递交换函数 [英] Passing arguments by pass-by-reference to a swap function

问题描述

我在解决练习测试时遇到了这个问题。考虑下面的代码以
FORTRAN之类的传递引用语言编写，并且这些语句代码

 子程序交换（ix，iy）
 it = ix 
 ix = iy！ L1行
 iy = it！在线L2 
结束
 
程序主要
 ia = 3 
 ib = 8 
调用交换（ia，ib + 5）
 print * ，ia，ib 
最终计划
  

陈述：

1. 编译器将生成代码来分配一个临时无名单元，
   将其初始化为13，并传递单元交换的地址
   
2. 执行时，代码将在第L1行生成运行时错误。


3. 执行时，代码将在第二行生成运行时错误。程序将打印13和8


4. 程序将打印13和-2

上面的声明是正确的。

我认为S1和S4。任何人都可以确认吗？ TIA

解决方案

是的，S1和S4都是正确的。

，

S0a：由于L1：和L2：是语法错误，所以文件不可编译。 ：）

S0b：严格来说，FORTRAN作为参考传递语言是不正确的：

• 语言的名称是Fortran




• 按引用传递的是未在标准中指定的实现细节。拷入，拷出是另一种可能的实现。此外，一些较新的Fortran语言功能（F90 +）实际上意味着既不是通过引用也不是copy-in-copy-out的实现。见例如指针作为虚拟参数和 http：// software .intel.com / en-us / blogs / 2009/03/31 / doctor-fortran-in-iive-come-here-for-an-argument /

I encountered this problem while solving a practice test

Consider the following code written in a pass-by-reference language like FORTRAN and these statements about the code

  subroutine swap(ix,iy)
    it = ix
    ix = iy    ! line L1
    iy = it    ! line L2
  end

  program main
    ia = 3
    ib = 8
    call swap (ia, ib+5)
    print *, ia, ib
  end program

Statements:

1. The compiler will generate code to allocate a temporary nameless cell, initialize it to 13, and pass the address of the cell swap
2. On execution the code will generate a runtime error on line L1
3. On execution the code will generate a runtime error on line L2
4. The program will print 13 and 8
5. The program will print 13 and -2

Which of the above the above statement(s) is/are correct.

I think S1 and S4. Could anyone please confirm? TIA

解决方案

Yes, S1 and S4 are correct.

Also,

S0a: The file is not compilable as is because the L1: and L2: are syntax errors. :)

S0b: Strictly speaking, speaking of FORTRAN as a pass-by-reference language is incorrect:

• The name of the language is Fortran

• Pass by reference is an implementation detail that is not specified in the standard. Copy-in, copy-out is another possible implementation. Also, some newer Fortran language features (F90+) in practice imply an implementation which is neither pass-by-reference nor copy-in-copy-out. See e.g. pointer as a dummy argument and http://software.intel.com/en-us/blogs/2009/03/31/doctor-fortran-in-ive-come-here-for-an-argument/

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