隐式转换整数< - >逻辑在Fortran if语句中 [英] Implicit conversion integer <--> logical in Fortran if statement

问题描述

我有一些遗留的Fortran代码，我被要求分析并翻译成现代语言。我不知道过去编译代码时使用了哪种编译器，所以现在我试着用gfortran编译它。代码中包含这样的语句导致gfortran投诉：

pre code>程序测试
隐式无
整数* 4 :: var
var = .true。

if（var）then
write（*，*）Hi
endif

end program test

使用gfortran编译此错误会导致以下错误：

  test.f：6：9：
 
 if（var）then 
 1 
错误：（1）处的IF子句需要标量LOGICAL表达式
  

（另外，它给出了在 var = .true中完成的转换的警告。 ）。

我不确定编译代码的哪个编译器，但显然代码应该按原样编译。有没有办法告诉gfortran接受这种转换？

根据文档，虽然在if语句中没有进行隐式转换： https://gcc.gnu.org/onlinedocs/gfortran/Implicitly-convert -LOGICAL-and-INTEGER-values.html

解决方案

这在GFortran中是不可能的。 手册指出：

但是，在
if语句中不存在INTEGER值的隐式转换，在I / O操作中也不存在LOGICAL或INTEGER值的隐式转换。

您只能在分配中执行隐式转换，例如您的

  integer :: var 
 var = .true。 
  

但即使如此，您也必须非常小心。它不符合标准，编译器之间的值 var 会有所不同。英特尔曾经使用 -1 （所有位设为1），除非选择 -standard-semantics code> .true。，但gfortran在C语言中使用 +1 。新版本的英特尔Fortran更改了默认设置。另一个方向更加棘手，可能有值不是 .true。也不是 .false。。 p>

I have some legacy Fortran code which I was asked to analyze and translate to a modern language. I don't know which compiler was used in the past to compile the code, so for now, I'm trying to compile it with gfortran. The code contains a statement like this was causes gfortran to complain:

  program test
  implicit none
  integer*4 :: var
  var=.true.

  if(var) then
        write(*,*) "Hi"
  endif

  end program test

Compiling this with gfortran gives the following error:

test.f:6:9:

       if(var) then
         1
Error: IF clause at (1) requires a scalar LOGICAL expression

(In addition, it gives a warning about the conversion done in var=.true.).

I'm not sure which which compiler the code was compiled, but apparently the code should compile as it is. Is there a way to tell gfortran to accept this conversion?

According to the docs, no implicit conversion is done within if-statements though: https://gcc.gnu.org/onlinedocs/gfortran/Implicitly-convert-LOGICAL-and-INTEGER-values.html

解决方案

This is not possible in GFortran. The manual states:

However, there is no implicit conversion of INTEGER values in if-statements, nor of LOGICAL or INTEGER values in I/O operations.

You are only able to perform implicit conversions in assignments like your

  integer :: var
  var = .true.

but even there you must be very careful. It is not standard conforming and the value var will differ between compilers. Intel used to use -1 (all bits set to 1), unless -standard-semantics was chosen, for .true., but gfortran uses +1 as in the C language. New versions of Intel Fortran changes the default. The other direction is even trickier, there might be values which are neither .true. nor .false..

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