--------------------Configuration: 02 - Win32 Debug-------------------- Compiling Fortran... D:\HJWFORTRAN\KESHE\02\2.f90 D:\HJWFORTRAN\KESHE\02\2.f90(32) : Error: This name does not have a type, and must have an explicit type. [RECTANGLE_METHOD] integral_result = rectangle_method(a, b, n) --------------------------------------^ D:\HJWFORTRAN\KESHE\02\2.f90(35) : Error: This name does not have a type, and must have an explicit type. [TRAPEZOIDAL_METHOD] integral_result = trapezoidal_method(a, b, n) --------------------------------------^ D:\HJWFORTRAN\KESHE\02\2.f90(38) : Error: This name does not have a type, and must have an explicit type. [SIMPSONS_METHOD] integral_result = simpsons_method(a, b, n) --------------------------------------^ Error executing df.exe. 02.exe - 3 error(s), 0 warning(s) 根据这个提示修改

根据编译器提示的错误信息，问题在于Fortran中调用子程序时，编译器无法识别`rectangle_method`、`trapezoidal_method`和`simpsons_method`的类型。这是因为Fortran要求在使用函数之前必须明确声明其类型。 为了解决这个问题，我们需要在主程序中使用`implicit none`语句，并通过`interface`块或模块（module）显式声明这些函数的接口。 以下是修改后的代码： ### 修改后的Fortran代码 ```fortran program definite_integral implicit none integer :: method, choice real :: a, b, integral_result integer :: n ! 主菜单循环 do call show_menu() read(*,*) choice select case (choice) case (1) ! 输入积分区间和分割数 print *, "Enter the lower limit (a):" read(*,*) a print *, "Enter the upper limit (b):" read(*,*) b print *, "Enter the number of intervals (n):" read(*,*) n case (2) ! 计算定积分 if (a >= b .or. n <= 0) then print *, "Invalid interval or number of intervals." else print *, "Choose the method to calculate the integral:" print *, "1. Rectangle Method" print *, "2. Trapezoidal Method" print *, "3. Simpson's Method" read(*,*) method select case (method) case (1) integral_result = rectangle_method(a, b, n) print *, "Integral by Rectangle Method:", integral_result case (2) integral_result = trapezoidal_method(a, b, n) print *, "Integral by Trapezoidal Method:", integral_result case (3) integral_result = simpsons_method(a, b, n) print *, "Integral by Simpson's Method:", integral_result case default print *, "Invalid method choice." end select end if case (3) ! 退出程序 exit case default print *, "Invalid choice. Please try again." end select end do contains ! 显示菜单 subroutine show_menu() print *, "Menu:" print *, "1. Input integration limits and intervals" print *, "2. Calculate definite integral" print *, "3. Exit" print *, "Enter your choice:" end subroutine show_menu ! 定义函数 f(x) real function f(x) real, intent(in) :: x f = x**2 + 2*x + 1 ! 每位同学可以选择不同的函数 end function f ! 矩形法求定积分 real function rectangle_method(a, b, n) real, intent(in) :: a, b integer, intent(in) :: n real :: h, xi integer :: i h = (b - a) / real(n) rectangle_method = 0.0 do i = 1, n xi = a + (i - 0.5) * h ! 取每个矩形的中点 rectangle_method = rectangle_method + f(xi) * h end do end function rectangle_method ! 梯形法求定积分 real function trapezoidal_method(a, b, n) real, intent(in) :: a, b integer, intent(in) :: n real :: h, xi integer :: i h = (b - a) / real(n) trapezoidal_method = 0.5 * (f(a) + f(b)) * h do i = 1, n-1 xi = a + i * h trapezoidal_method = trapezoidal_method + f(xi) * h end do end function trapezoidal_method ! 辛普生法求定积分 real function simpsons_method(a, b, n) real, intent(in) :: a, b integer, intent(in) :: n real :: h, xi integer :: i if (mod(n, 2) /= 0) then print *, "For Simpson's method, n must be even." simpsons_method = 0.0 return end if h = (b - a) / real(n) simpsons_method = f(a) + f(b) do i = 1, n-1 xi = a + i * h if (mod(i, 2) == 0) then simpsons_method = simpsons_method + 2.0 * f(xi) else simpsons_method = simpsons_method + 4.0 * f(xi) end if end do simpsons_method = simpsons_method * h / 3.0 end function simpsons_method end program definite_integral ``` --- ### 解释修改内容 1. **`contains`关键字**： - 在Fortran中，如果将子程序定义在`contains`块内，则它们会自动成为主程序的一部分，编译器可以正确识别它们的类型。 - 这样就不需要额外的`interface`声明。 2. **`implicit none`**： - `implicit none`确保所有变量都必须显式声明类型，避免隐式类型推断可能导致的错误。 3. **函数接口**： - 将所有函数定义在`contains`块内后，编译器能够自动识别函数的返回值类型（如`real`），从而解决“没有显式类型”的问题。 --- ###