如何在Fortran的main.f95中正确导入roll_dice.f95子程序？

错误原因 #

你遇到的编译错误本质是Fortran语法规则限制：当用include将子程序代码插入主程序时，子程序不能直接放在主程序的执行语句区域（比如call语句前后）。主程序的结构要求，内部子程序必须放在contains块中；如果要作为独立文件的外部子程序，需要用模块或者分开编译链接。

另外你代码里还有两个小问题：

• 输出骰子图案时的反斜杠\是多余的，Fortran不需要转义加号，会导致输出多余的反斜杠
• 最后输出掷骰结果的格式串"('You rolled a ', 5(i0, ' and ', i0))"有误，5是多余的，会导致格式不匹配

解决方法一：修正include的用法（适合简单场景） #

把include放在主程序的contains块中，让子程序成为主程序的内部子程序：

修改后的main.f95 #

program main
    implicit none

    ! 这里可以声明变量或添加use语句
    call roll_dice() ! 调用子程序

contains
    ! 将子程序文件包含在contains块内，符合Fortran语法
    include 'roll_dice.f95'

end program main

修正后的roll_dice.f95 #

去掉多余的反斜杠，修正格式串：

subroutine roll_dice()
    real :: r(2)
    integer :: i(2)

    call random_seed()
    call random_number(r)

    ! 转换为1-6的整数
    i = 1 + nint(5 * r)

    ! 第一个骰子图案
    select case (i(1))
    case (1)
        print *, "+-------+"
        print *, "|       |"
        print *, "|   *   |"
        print *, "|       |"
        print *, "+-------+"
    case (2)
        print *, "+-------+"
        print *, "|     * |"
        print *, "|       |"
        print *, "| *     |"
        print *, "+-------+"
    case (3)
        print *, "+-------+"
        print *, "|     * |"
        print *, "|   *   |"
        print *, "| *     |"
        print *, "+-------+"
    case (4)
        print *, "+-------+"
        print *, "| *   * |"
        print *, "|       |"
        print *, "| *   * |"
        print *, "+-------+"
    case (5)
        print *, "+-------+"
        print *, "| *   * |"
        print *, "|   *   |"
        print *, "| *   * |"
        print *, "+-------+"
    case (6)
        print *, "+-------+"
        print *, "| *   * |"
        print *, "| *   * |"
        print *, "| *   * |"
        print *, "+-------+"
    case default
        print *, "第一个随机数无效"
    end select

    ! 第二个骰子图案
    select case (i(2))
    case (1)
        print *, "+-------+"
        print *, "|       |"
        print *, "|   *   |"
        print *, "|       |"
        print *, "+-------+"
    case (2)
        print *, "+-------+"
        print *, "|     * |"
        print *, "|       |"
        print *, "| *     |"
        print *, "+-------+"
    case (3)
        print *, "+-------+"
        print *, "|     * |"
        print *, "|   *   |"
        print *, "| *     |"
        print *, "+-------+"
    case (4)
        print *, "+-------+"
        print *, "| *   * |"
        print *, "|       |"
        print *, "| *   * |"
        print *, "+-------+"
    case (5)
        print *, "+-------+"
        print *, "| *   * |"
        print *, "|   *   |"
        print *, "| *   * |"
        print *, "+-------+"
    case (6)
        print *, "+-------+"
        print *, "| *   * |"
        print *, "| *   * |"
        print *, "| *   * |"
        print *, "+-------+"
    case default
        print *, "第二个随机数无效"
    end select
    
    ! 修正格式串，正确输出两个骰子的点数
    print "('你掷出了 ', i0, ' 和 ', i0)", i

end subroutine roll_dice

编译运行：

gfortran main.f95 -o dice_game
./dice_game

解决方法二：使用Fortran模块（推荐，适合大型模块化程序） #

这是Fortran标准的模块化编程方式，更适合后续扩展多个子程序的场景：

修改后的roll_dice.f95（改为模块） #

module dice_mod
    implicit none
contains
    subroutine roll_dice()
        real :: r(2)
        integer :: i(2)

        call random_seed()
        call random_number(r)

        ! 转换为1-6的整数
        i = 1 + nint(5 * r)

        ! 第一个骰子图案
        select case (i(1))
        case (1)
            print *, "+-------+"
            print *, "|       |"
            print *, "|   *   |"
            print *, "|       |"
            print *, "+-------+"
        case (2)
            print *, "+-------+"
            print *, "|     * |"
            print *, "|       |"
            print *, "| *     |"
            print *, "+-------+"
        case (3)
            print *, "+-------+"
            print *, "|     * |"
            print *, "|   *   |"
            print *, "| *     |"
            print *, "+-------+"
        case (4)
            print *, "+-------+"
            print *, "| *   * |"
            print *, "|       |"
            print *, "| *   * |"
            print *, "+-------+"
        case (5)
            print *, "+-------+"
            print *, "| *   * |"
            print *, "|   *   |"
            print *, "| *   * |"
            print *, "+-------+"
        case (6)
            print *, "+-------+"
            print *, "| *   * |"
            print *, "| *   * |"
            print *, "| *   * |"
            print *, "+-------+"
        case default
            print *, "第一个随机数无效"
        end select

        ! 第二个骰子图案
        select case (i(2))
        case (1)
            print *, "+-------+"
            print *, "|       |"
            print *, "|   *   |"
            print *, "|       |"
            print *, "+-------+"
        case (2)
            print *, "+-------+"
            print *, "|     * |"
            print *, "|       |"
            print *, "| *     |"
            print *, "+-------+"
        case (3)
            print *, "+-------+"
            print *, "|     * |"
            print *, "|   *   |"
            print *, "| *     |"
            print *, "+-------+"
        case (4)
            print *, "+-------+"
            print *, "| *   * |"
            print *, "|       |"
            print *, "| *   * |"
            print *, "+-------+"
        case (5)
            print *, "+-------+"
            print *, "| *   * |"
            print *, "|   *   |"
            print *, "| *   * |"
            print *, "+-------+"
        case (6)
            print *, "+-------+"
            print *, "| *   * |"
            print *, "| *   * |"
            print *, "| *   * |"
            print *, "+-------+"
        case default
            print *, "第二个随机数无效"
        end select
        
        ! 修正格式串
        print "('你掷出了 ', i0, ' 和 ', i0)", i

    end subroutine roll_dice
end module dice_mod

修改后的main.f95（使用模块） #

program main
    ! 导入模块，这样就能使用其中的子程序
    use dice_mod
    implicit none

    call roll_dice() ! 调用模块中的子程序

end program main

编译运行：

# 方式一：分开编译
gfortran -c roll_dice.f95
gfortran main.f95 roll_dice.o -o dice_game
./dice_game

# 方式二：一次性编译
gfortran main.f95 roll_dice.f95 -o dice_game
./dice_game

内容的提问来源于stack exchange，提问作者Jace