What is the cause of these error- symbol 'x1' has no implicit type?

[s_hy]

Hi all,

i am beginner in fortran and linux. I have wrote codes for 1d scalar wave as below:

SUBROUTINE fd1d (x_num,x1,x2,t_num,t1,t2,c,u_x1,u_x2,u_t1,ut_t1,u)
implicit none
integer (kind=2) t_num,x_num,t,x
real (kind=4) alpha,c,t_delta,t1,t2,u(t_num+1,x_num+1),ut(x_num+1),x_delta,x1,x2
t_delta = (t2-t1)/real(t_num,kind=4)
x_delta = (x2-x1)/real(x_num,kind=4)
alpha = c*t_delta/x_delta
write ( *,'(a)')''
write ( *,'a,g14.6)') 'Stability condition ALPHA = C * DT/DX = ',alpha
Open (103, FILE='parameters.DAT',status='old')
Open(90, File = "abc.dat", ACCESS = 'APPEND')

!the boundary conditions
call u_x1 ( t_num,x_num,u )
call u_x2 ( t_num,x_num,u )

!the initial data
call u_t1 ( t_num,x_num,u )
call ut_t1( x_num,ut )

t=1
do x=2, x_num
u(t+1,x) = alpha**2 * u(t,x+1) / 2.0D+00 + ( 1.0D+00-alpha**2 ) * u(t,x) &
+ alpha**2 * u(t,x-1) / 2.0D+00 + t_delta * ut(x)
end do

!All subsequent steps in time rely on two previous rows of solution data

do t=2, t_num
do x=2, x_num
u(t+1,x) = alpha**2 * u(t, x+1) + 2.0D+00 * (1.0D+00-alpha**2) * u(t, x) &
+ alpha**2 * u(t, x-1) - u(t-1,x)
end do
end do
return
end SUBROUTINE fd1d


when i am trying to compile, there are errors referring to all parameters which is "symbol 'x1' (and t1, c, x2...) has no implicit type. What is that mean?

 

[Mark44]

The variables that you list (x1, t1, c, and x2) are declared in the subroutine you showed, so my guess is that the error arises in some other part of your program, a part you didn't show us. Are these variables being used elsewhere in your program? If so, they probably aren't being declared in those places.

What we aren't seeing is the main program and the four subroutines that are called in the code above, plus whatever else makes up the entire program.

The compiler or linker probably gave more information than you showed, such as the line number at which the error occurred. That information can help you narrow down the source of the problem.

 

[s_hy]

thank you for ur time mark44. the list of subroutines that i didn't list here are quite long, might be bothering. I have found out the problem and finally have succeed to compile it without any error.

thanks again

 

[LaurieAG]

Hi guys,

The variables that you list (x1, t1, c, and x2) are declared in the subroutine you showed, so my guess is that the error arises in some other part of your program, a part you didn't show us.

The variables were re declared in the subroutine after being passed from the main program.

s_hy, see what happens when you change types between the main and the subroutine for future reference.

The windows wobble bug was similar and caused approx 60,000 programs to have errors when run in win 2000 (NT). The win com/com+ model created an extra thread on early dual processor systems that ran out after 8 ocurrences of a subroutine type change error.

 

[LudusRex]

The cause of this error is that the variables x1, t1, c, and x2 have not been declared with an explicit type. In Fortran, all variables must have an explicit type, such as integer or real, declared before they can be used in a program. This is known as implicit typing.

To fix this error, you will need to declare the type of each variable before using it in your program. For example, you could declare x1 as a real variable by adding the line "real (kind=4) :: x1" before the subroutine declaration. This will ensure that the compiler knows what type of variable x1 is and can properly use it in the program.

It is important to explicitly declare the type of all variables in your program to avoid errors and ensure that your code runs correctly. Additionally, it is good practice to initialize all variables with a value before using them in your program. This will help prevent any unexpected behavior and improve the overall quality of your code.