Fortran:整数 * 4 与整数(4)与整数(种类 = 4) [英] Fortran: integer*4 vs integer(4) vs integer(kind=4)

问题描述

我正在努力学习 Fortran，我看到很多不同的定义被传递，我想知道他们是否正在尝试完成同样的事情.以下有什么区别?

I'm trying to learn Fortran and I'm seeing a lot of different definitions being passed around and I'm wondering if they're trying to accomplish the same thing. What is the difference between the following?

• 整数*4
• 整数(4)
• 整数(kind=4)

推荐答案

在 Fortran >=90 中，最好的方法是使用内部函数来指定您需要的精度——这既保证了可移植性，又保证了您获得所需的精度需要.例如，要获得至少支持 8 个十进制数字的整数 i 和 my_int，您可以使用:

In Fortran >=90, the best approach is use intrinsic functions to specify the precision you need -- this guarantees both portability and that you get the precision that you need. For example, to obtain integers i and my_int that will support at least 8 decimal digits, you could use:

integer, parameter :: RegInt_K = selected_int_kind (8)
integer (kind=RegInt_K) :: i, my_int

已将 RegInt_K(或您选择的任何名称)定义为 parameter，您可以在整个代码中将其用作符号.这也使更改精度变得容易.

Having defined RegInt_K (or whatever name you select) as a parameter, you can use it throughout your code as a symbol. This also makes it easy to change the precision.

请求 8 位或 9 位十进制数字通常会获得一个 4 字节整数.

Requesting 8 or 9 decimal digits will typically obtain a 4-byte integer.

integer*4 是一个常见的扩展，可以追溯到旧的 FORTRAN 以指定一个 4 字节整数.虽然，这种语法不是，也从来不是标准的 Fortran.

integer*4 is an common extension going back to old FORTRAN to specify a 4-byte integer. Although, this syntax isn't and was never standard Fortran.

integer (4) 或 integer (RegInt_K) 是 integer (kind=4) 或 integer (kind=RegInt_K).integer (4) 与 integer*4 不同，并且不可移植——语言标准没有指定种类的数值.大多数编译器将 kind=4 用于 4 字节整数——因为这些编译器 integer*4 和 integer(4) 将提供相同的整数类型——但也有例外，所以 integer(4) 是不可移植的，最好避免使用.

integer (4) or integer (RegInt_K) are short for integer (kind=4) or integer (kind=RegInt_K). integer (4) is not the same as integer*4 and is non-portable -- the language standard does not specify the numeric values of kinds. Most compilers use the kind=4 for 4-byte integers -- for these compilers integer*4 and integer(4) will provide the same integer type -- but there are exceptions, so integer(4) is non-portable and best avoided.

实数的方法类似.

更新:如果您不想通过所需的精度指定数字类型，而是通过它们将使用的存储来指定，Fortran 2008 提供了一种方法.实数和整数可以通过 use 使用 ISO_FORTRAN_ENV 模块后的存储位数指定，例如，对于 4 字节(32 位)整数:

UPDATE: if you don't want to specify numeric types by the required precision, but instead by the storage that they will use, Fortran 2008 provides a method. reals and integers can be specified by the number of bits of storage after useing the ISO_FORTRAN_ENV module, for example, for a 4-byte (32-bit) integer:

use ISO_FORTRAN_ENV
integer (int32) :: MyInt

gfortran 手册在内在模块"下有文档.

The gfortran manual has documentation under "intrinsic modules".

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