在 Fortran 90 中使用模块内部的子例程

我有一个关于在 Fortran 90 中的模块内使用子例程的问题。这是我的代码

    Module Multiplication
      Subroutine Two_times(input,output)
        Real :: input,output  
        output = input * 2.0  
      End Subroutine Two_times
    End Module    
    Program test_get_command_argument
      Use Multiplication: Two_times

      Real :: i,j

      i = 0.5
      Write (*,*) i

      Call  Two_times(i,j)
      Write (*,*) j

    End Program

我使用ifort编译了上面的代码。我收到以下消息。

    files_rev.f90(2): error #6218: This statement is positioned incorrectly and/or has syntax errors.
      Subroutine Two_times(input,output)
    --^
    files_rev.f90(4): error #6274: This statement must not appear in the specification part of a module.
        output = input * 2.0  
    ----^
    files_rev.f90(5): error #6786: This is an invalid statement; an END [MODULE] statement is required.
      End Subroutine Two_times
    --^
    files_rev.f90(5): error #6785: This name does not match the unit name.   [TWO_TIMES]
      End Subroutine Two_times
    -----------------^
    files_rev.f90(6): error #6790: This is an invalid statement; an END [PROGRAM]  statement is required.
    End Module 
    ^
    files_rev.f90(9): error #5082: Syntax error, found IDENTIFIER 'MULTIPLICATION' when expecting one of: ( : % [ . = =>
      Use Multiplication: Two_times
    ------^
    files_rev.f90(8): warning #5427: Program may contain only one main entry routine
    Program test_get_command_argument
    --------^
    compilation aborted for files_rev.f90 (code 1)

为什么我收到 #6218 和 #6274 错误消息以及如何修复它们？

你缺少一个contains之前的关键字subroutine声明和only之后的关键字use。或者你可以删除: Two_times使用模块中的所有内容。所以工作代码如下所示：

Module Multiplication
  Contains
  Subroutine Two_times(input,output)
    Real :: input,output  
    output = input * 2.0  
  End Subroutine Two_times
End Module 

Program test_get_command_argument
  Use Multiplication, Only: Two_times
  Real :: i,j

  i = 0.5
  Write (*,*) i

  Call Two_times(i,j)
  Write (*,*) j

End Program

看看这个答案，无法在同一文件中使用模块和主程序进行编译，同样，对于失踪者contains.