Fortran中包含子程序和函数的模块

Question

我正在学习正确使用子程序，函数和模块，下面是一个简单的例子，编译时没有发生错误，执行后，结果是4.57187637E-41而不是pi，我查了几个引用，还没有发现错误。

module wz 
    implicit none 
    private 
    public :: print_out 
    real,parameter :: pi = 3.14159 
    contains 
     subroutine print_out 
     implicit none 
     real :: area 
     print *, area 
     end subroutine print_out 

     function f(x) result(area) 
     implicit none 

     real, intent(in):: x 
     real   :: area 

     area = pi * x ** 2 
     end function f 
end module wz 

program test_module 
use wz 
implicit none 
    real :: x 
    x = 1. 
    call print_out 
end program test_module 

Answer 1

您正在打印的值是area，只是在声明之后以及在做任何事情之前。你需要传递x到f功能，你可以做到这一点通过print_out子程序：

module wz 
    implicit none 
    private 
    public :: print_out 
    real,parameter :: pi = 3.14159 
    contains 
     subroutine print_out(x) 
     implicit none 
     real, intent(in) :: x 
     real :: area 
     area = f(x) 
     print *, area 
     end subroutine print_out 

     function f(x) result(area) 
     implicit none 

     real, intent(in):: x 
     real   :: area 

     area = pi * x ** 2 
     end function f 
end module wz 

program test_module 
use wz 
implicit none 
    real :: x 
    x = 1. 
    call print_out(x) 
end program test_module